diff mbox

[v4] Add and use new glibc-internal futex API.

Message ID 1435749621.4216.64.camel@localhost.localdomain
State Dropped
Headers show

Commit Message

Torvald Riegel July 1, 2015, 11:20 a.m. UTC
On Wed, 2015-06-24 at 16:22 -0700, Roland McGrath wrote:
> > @@ -987,7 +988,8 @@ setxid_mark_thread (struct xid_command *cmdp, struct pthread *t)
> >    if (t->setxid_futex == -1
> >        && ! atomic_compare_and_exchange_bool_acq (&t->setxid_futex, -2, -1))
> >      do
> > -      lll_futex_wait (&t->setxid_futex, -2, LLL_PRIVATE);
> > +      futex_wait_simple ((unsigned int *) &t->setxid_futex, -2,
> > +			 FUTEX_PRIVATE);
> >      while (t->setxid_futex == -2);
> 
> All these casts are ugly.  Where possible, we should just change the types
> of the fields to unsigned int.  For setxid_futex, it appears to use exactly
> four values (0, 1, -1, -2) and the particular choice of values does not
> seem to matter (except perhaps 0 as initialization state).  So really these
> should be in an enum rather than hard-coded magic numbers.
> 
> Cleaning that up could be done either before or after the futex API
> changes.  But I tend to think that if we have these explicit casts around,
> we'll fail to remove them all later when we should.

I've removed the casts.  The clean-up to enums should be done with the
patch that uses atomics to access setxid_futex.

(Note that the lack of atomic accesses to futex words is a recurring
problem, and not one I intended to solve with this patch.)

> > --- a/nptl/cancellation.c
> > +++ b/nptl/cancellation.c
> > @@ -19,6 +19,7 @@
> >  #include <setjmp.h>
> >  #include <stdlib.h>
> >  #include "pthreadP.h"
> > +#include <futex-internal.h>
> >  
> >  
> >  /* The next two functions are similar to pthread_setcanceltype() but
> > @@ -93,7 +94,7 @@ __pthread_disable_asynccancel (int oldtype)
> >    while (__builtin_expect ((newval & (CANCELING_BITMASK | CANCELED_BITMASK))
> >  			   == CANCELING_BITMASK, 0))
> >      {
> > -      lll_futex_wait (&self->cancelhandling, newval, LLL_PRIVATE);
> > +      futex_wait_simple (&self->cancelhandling, newval, FUTEX_PRIVATE);
> 
> This fails to build because of int vs unsigned int.  x86_64 has assembly
> code for this file, so you didn't test it in your build.  Please do at
> least an i686 build too to catch more cases.
> 
> Here too, the field really should just be unsigned int rather than adding
> casts everywhere.

ISTM the cancelhandling change to unsigned int requires more pervasive
code changes than in the patch you posted (see my reply to that).
I've kept the casts for now, with the expectation that we'll change to
unsigned int in the patch that uses atomics for all accesses to
cancelhandling.

> > +  int futex_private = (lll_private == LLL_PRIVATE)
> > +		      ? FUTEX_PRIVATE : FUTEX_SHARED;
> 
> There's no need for parens around a comparison like that.
> The operator precedence of comparison operators for ?: is well-known.
> However, you should use parens differently here so that the second
> line's indentation is done right (and stays that way):
> 
>   int futex_private = (lll_private == LLL_PRIVATE
> 		       ? FUTEX_PRIVATE : FUTEX_SHARED);

Changed to not use parens except where it's a multi-line case like
above.

> > @@ -31,6 +32,10 @@ pthread_mutexattr_setpshared (attr, pshared)
> >        && __builtin_expect (pshared != PTHREAD_PROCESS_SHARED, 0))
> >      return EINVAL;
> >  
> > +  int err = futex_supports_pshared (pshared);
> > +  if (err != 0)
> > +    return err;
> 
> It wouldn't hurt to consolidate the EINVAL check and futex_supports_pshared
> into one function that these several places could all call instead of
> duplicating the code.

futex_supports_pshared now checks whether pshared is one of the two
allowed values, too.

> > +    /* No other errors are documented at this time.  */
> > +    default:
> > +      abort ();
> 
> I think all these abort calls should be __libc_fatal, or perhaps
> __libc_message that shows the actual unexpected error code value.
> (Actually, they should all use a common convenience function for that.)

Added a convenience function called futex_fatal_error.

> > +/* See sysdeps/nptl/futex-internal.h for details.  */
> > +static __always_inline void
> > +futex_wait_simple (unsigned int *futex_word, unsigned int expected,
> > +		   int private)
> > +{
> > +  ignore_value (futex_wait (futex_word, expected, private));
> > +}
> 
> This obviously is not actually system-dependent and does not need to be
> copied.  But I'm not sure where we'd put it.  Perhaps there should be a
> common header that defines this and the convenience function for the abort
> cases (and maybe other things).  It could be a wrapper header that includes
> the sysdeps header.  It could be a little header that each variant
> includes.  It could be just in sysdeps/nptl/futex-internal.h and all the
> variants include that first; that might be best, in that the common file
> pre-declares all the inlines and thus we'd get compile-time checking that
> each variant is actually using all the correct signatures in its
> implementation.

I'm now including sysdeps/nptl/futex-internal.h from the
platform-specific futex-internal.h files.  futex_wait_simple goes there
as well as futex_fatal_error.

> >  #define AIO_MISC_NOTIFY(waitlist) \
> >    do {									      \
> >      if (*waitlist->counterp > 0 && --*waitlist->counterp == 0)		      \
> > -      lll_futex_wake (waitlist->counterp, 1, LLL_PRIVATE);		      \
> > +      futex_wake ((unsigned int *) waitlist->counterp, 1, FUTEX_PRIVATE);     \
> >    } while (0)
> 
> Another field whose type should change.

Can't do that right now because it still needs to cast away the volatile
that's still present after your recent change that makes it volatile
unsigned int.  I don't want to just remove the volatile either, because
this way make the synchronization work (it really should use atomics
though).  This can be cleaned up when we transform this to using
atomics.

> > +/* futex operations for glibc-internal use.  Stub version.
> > +   Copyright (C) 2014-2015 Free Software Foundation, Inc.
> 
> If you didn't copy any of this content from other files that had a 2014
> copyright, then a new file should just have a 2015 copyright.

I had posted this last year, and I remember that this is considered the
"publication" of the code.

> > +/* Returns 0 if PSHARED is supported, which can be either
> > +   PTHREAD_PROCESS_PRIVATE or PTHREAD_PROCESS_SHARED.  Otherwise, returns
> > +   ENOTSUP.  */
> > +static __always_inline int
> > +futex_supports_pshared (int pshared);
> 
> If the interface is defined this tightly, then I don't see any benefit over
> making it bool(void).

Which would have been roughly the interface I had in a previous version
of this patch :)

Anyway, it now also checks that pshared is one of
PTHREAD_PROCESS_PRIVATE or PTHREAD_PROCESS_SHARED too (see above), so
returning an actual error code is fine now.

Updated patch is attached.  Once this is OK, I'll send an updated patch
that includes the (updated) sparc changes so that Dave can test (per
Joseph's request, to allow for bisect-ability, we can't have a separate
patch for the sparc bits).

Tested on x86_64-linux.  No regressions except that I am getting a
check-local-headers failure:
*** $(common-objpfx)stdio-common/scanf15.o:
uses /usr/include/bits/syscall.h
*** /usr/include/bits/syscall.h: uses /usr/include/bits/syscall.h:
*** $(common-objpfx)stdio-common/scanf17.o:
uses /usr/include/bits/syscall.h
*** /usr/include/bits/syscall.h: uses /usr/include/bits/syscall.h:
Any advice on how to fix that?

Comments

Torvald Riegel July 1, 2015, 2:10 p.m. UTC | #1
On Wed, 2015-07-01 at 13:20 +0200, Torvald Riegel wrote:
> Tested on x86_64-linux.  No regressions except that I am getting a
> check-local-headers failure:
> *** $(common-objpfx)stdio-common/scanf15.o:
> uses /usr/include/bits/syscall.h
> *** /usr/include/bits/syscall.h: uses /usr/include/bits/syscall.h:
> *** $(common-objpfx)stdio-common/scanf17.o:
> uses /usr/include/bits/syscall.h
> *** /usr/include/bits/syscall.h: uses /usr/include/bits/syscall.h:
> Any advice on how to fix that?

And that regression goes away with a fresh build, not an incremental
build.  Sigh.
Andreas Schwab July 1, 2015, 2:24 p.m. UTC | #2
Torvald Riegel <triegel@redhat.com> writes:

> On Wed, 2015-07-01 at 13:20 +0200, Torvald Riegel wrote:
>> Tested on x86_64-linux.  No regressions except that I am getting a
>> check-local-headers failure:
>> *** $(common-objpfx)stdio-common/scanf15.o:
>> uses /usr/include/bits/syscall.h
>> *** /usr/include/bits/syscall.h: uses /usr/include/bits/syscall.h:
>> *** $(common-objpfx)stdio-common/scanf17.o:
>> uses /usr/include/bits/syscall.h
>> *** /usr/include/bits/syscall.h: uses /usr/include/bits/syscall.h:
>> Any advice on how to fix that?
>
> And that regression goes away with a fresh build, not an incremental
> build.  Sigh.

The only reason you don't get the failure with a fresh build is that
check-local-headers runs when the *.dt files of all the test programs
are not yet converted into *.d files.

Andreas.
Torvald Riegel July 1, 2015, 4:38 p.m. UTC | #3
On Wed, 2015-07-01 at 16:24 +0200, Andreas Schwab wrote:
> Torvald Riegel <triegel@redhat.com> writes:
> 
> > On Wed, 2015-07-01 at 13:20 +0200, Torvald Riegel wrote:
> >> Tested on x86_64-linux.  No regressions except that I am getting a
> >> check-local-headers failure:
> >> *** $(common-objpfx)stdio-common/scanf15.o:
> >> uses /usr/include/bits/syscall.h
> >> *** /usr/include/bits/syscall.h: uses /usr/include/bits/syscall.h:
> >> *** $(common-objpfx)stdio-common/scanf17.o:
> >> uses /usr/include/bits/syscall.h
> >> *** /usr/include/bits/syscall.h: uses /usr/include/bits/syscall.h:
> >> Any advice on how to fix that?
> >
> > And that regression goes away with a fresh build, not an incremental
> > build.  Sigh.
> 
> The only reason you don't get the failure with a fresh build is that
> check-local-headers runs when the *.dt files of all the test programs
> are not yet converted into *.d files.

OK, I see that now.  Is that intentional?  Or does check-local-headers
simply not work with fresh builds (which would be surprising..)?

Any further feedback on whether the actual failure reported on a
non-fresh-build makes sense, and how to fix it?
Andreas Schwab July 1, 2015, 6:04 p.m. UTC | #4
Torvald Riegel <triegel@redhat.com> writes:

> OK, I see that now.  Is that intentional?  Or does check-local-headers
> simply not work with fresh builds (which would be surprising..)?

The latter, but only for testsuite dep files (the others were already
converted during the testsuite run the latest).

> Any further feedback on whether the actual failure reported on a
> non-fresh-build makes sense, and how to fix it?

Really the two tests are broken by design:

# The following is a hack since we must compile scanf1{5,7}.c without any
# GNU extension.  The latter are needed, though, when internal headers
# are used.  So made sure we see the installed headers first.

Andreas.
Roland McGrath July 2, 2015, 1:27 a.m. UTC | #5
> I've removed the casts.  The clean-up to enums should be done with the
> patch that uses atomics to access setxid_futex.
> 
> (Note that the lack of atomic accesses to futex words is a recurring
> problem, and not one I intended to solve with this patch.)

Agreed.

> ISTM the cancelhandling change to unsigned int requires more pervasive
> code changes than in the patch you posted (see my reply to that).
> I've kept the casts for now, with the expectation that we'll change to
> unsigned int in the patch that uses atomics for all accesses to
> cancelhandling.

OK.  Anything is fine with me as long as by the end we clean things up to
remove all the casts.

> I'm now including sysdeps/nptl/futex-internal.h from the
> platform-specific futex-internal.h files.  futex_wait_simple goes there
> as well as futex_fatal_error.

That should be fine.  It wouldn't hurt to pass the errno value and perhaps
a string naming the operation to futex_fatal_error.  Then we can later
change it to call __libc_message (1, ...) for a more informative error.
(__libc_fatal takes a plain string, but __libc_message takes a minimal
printf-style format.)

> Can't do that right now because it still needs to cast away the volatile
> that's still present after your recent change that makes it volatile
> unsigned int.  I don't want to just remove the volatile either, because
> this way make the synchronization work (it really should use atomics
> though).  This can be cleaned up when we transform this to using
> atomics.

Agreed.  Perhaps every cast you add should have a formulaic (greppable)
comment so we can be sure we find them all in the later cleanup passes.

> I had posted this last year, and I remember that this is considered the
> "publication" of the code.

OK.

> Updated patch is attached.  Once this is OK, I'll send an updated patch
> that includes the (updated) sparc changes so that Dave can test (per
> Joseph's request, to allow for bisect-ability, we can't have a separate
> patch for the sparc bits).

I didn't check it closely, nor test it on NaCl.  I won't get to that until
next week.  (I'm actually on vacation this whole week, and just checking in
today to make sure I wasn't blocking you.)  Since we've resolved the issues
I raised, I'm sure it will be fine now.  I would appreciate if you could
amend it with greppable comments for everything we agreed we should clean
up later.  But beyond that if it has no regressions and nobody else
objects, it's fine with me to commit now.  If it turns out NaCl is actually
broken, I'll fix it up next week.

It wouldn't hurt to write up somewhere, probably on the wiki (though in
code comments in this patch would also be fine by me) the known/intended
further steps of transition and cleanup in this area.  I imagine that this
patch and maybe a bit more trivia is about all we'll get done before the
coming release freeze.  In practice that tends to mean we stop thinking
about the details for a month (and then that bleeds into August travel and
vacations and it always winds up longer than we intend before we get back
to it), so it seems wise to make the short-term future plans clear now
while the current discussion is fresh (and record them someplace easier to
follow than scattered in these review threads).


Thanks,
Roland
diff mbox

Patch

commit a691e8d2b4c973c168ba4e566b9d402f4f5f2b2b
Author: Torvald Riegel <triegel@redhat.com>
Date:   Thu Dec 4 14:12:23 2014 +0100

    Add and use new glibc-internal futex API.
    
    This adds new functions for futex operations, starting with wait,
    abstimed_wait, reltimed_wait, wake.  They add documentation and error
    checking according to the current draft of the Linux kernel futex manpage.
    
    Waiting with absolute or relative timeouts is split into separate functions.
    This allows for removing a few cases of code duplication in pthreads code,
    which uses absolute timeouts; also, it allows us to put platform-specific
    code to go from an absolute to a relative timeout into the platform-specific
    futex abstractions..
    
    Futex operations that can be canceled are also split out into separate
    functions suffixed by "_cancelable".
    
    There are separate versions for both Linux and NaCl; while they currently
    differ only slightly, my expectation is that the separate versions of
    lowlevellock-futex.h will eventually be merged into futex-internal.h
    when we get to move the lll_ functions over to the new futex API.

diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index 8e620c4..c56a4df 100644
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -29,6 +29,7 @@ 
 #include <tls.h>
 #include <list.h>
 #include <lowlevellock.h>
+#include <futex-internal.h>
 #include <kernel-features.h>
 #include <stack-aliasing.h>
 
@@ -987,7 +988,7 @@  setxid_mark_thread (struct xid_command *cmdp, struct pthread *t)
   if (t->setxid_futex == -1
       && ! atomic_compare_and_exchange_bool_acq (&t->setxid_futex, -2, -1))
     do
-      lll_futex_wait (&t->setxid_futex, -2, LLL_PRIVATE);
+      futex_wait_simple (&t->setxid_futex, -2, FUTEX_PRIVATE);
     while (t->setxid_futex == -2);
 
   /* Don't let the thread exit before the setxid handler runs.  */
@@ -1005,7 +1006,7 @@  setxid_mark_thread (struct xid_command *cmdp, struct pthread *t)
 	  if ((ch & SETXID_BITMASK) == 0)
 	    {
 	      t->setxid_futex = 1;
-	      lll_futex_wake (&t->setxid_futex, 1, LLL_PRIVATE);
+	      futex_wake (&t->setxid_futex, 1, FUTEX_PRIVATE);
 	    }
 	  return;
 	}
@@ -1032,7 +1033,7 @@  setxid_unmark_thread (struct xid_command *cmdp, struct pthread *t)
 
   /* Release the futex just in case.  */
   t->setxid_futex = 1;
-  lll_futex_wake (&t->setxid_futex, 1, LLL_PRIVATE);
+  futex_wake (&t->setxid_futex, 1, FUTEX_PRIVATE);
 }
 
 
@@ -1141,7 +1142,8 @@  __nptl_setxid (struct xid_command *cmdp)
       int cur = cmdp->cntr;
       while (cur != 0)
 	{
-	  lll_futex_wait (&cmdp->cntr, cur, LLL_PRIVATE);
+	  futex_wait_simple ((unsigned int *) &cmdp->cntr, cur,
+			     FUTEX_PRIVATE);
 	  cur = cmdp->cntr;
 	}
     }
@@ -1251,7 +1253,8 @@  __wait_lookup_done (void)
 	continue;
 
       do
-	lll_futex_wait (gscope_flagp, THREAD_GSCOPE_FLAG_WAIT, LLL_PRIVATE);
+	futex_wait_simple ((unsigned int *) gscope_flagp,
+			   THREAD_GSCOPE_FLAG_WAIT, FUTEX_PRIVATE);
       while (*gscope_flagp == THREAD_GSCOPE_FLAG_WAIT);
     }
 
@@ -1273,7 +1276,8 @@  __wait_lookup_done (void)
 	continue;
 
       do
-	lll_futex_wait (gscope_flagp, THREAD_GSCOPE_FLAG_WAIT, LLL_PRIVATE);
+	futex_wait_simple ((unsigned int *) gscope_flagp,
+			   THREAD_GSCOPE_FLAG_WAIT, FUTEX_PRIVATE);
       while (*gscope_flagp == THREAD_GSCOPE_FLAG_WAIT);
     }
 
diff --git a/nptl/cancellation.c b/nptl/cancellation.c
index deac1eb..2bd3168 100644
--- a/nptl/cancellation.c
+++ b/nptl/cancellation.c
@@ -19,6 +19,7 @@ 
 #include <setjmp.h>
 #include <stdlib.h>
 #include "pthreadP.h"
+#include <futex-internal.h>
 
 
 /* The next two functions are similar to pthread_setcanceltype() but
@@ -93,7 +94,8 @@  __pthread_disable_asynccancel (int oldtype)
   while (__builtin_expect ((newval & (CANCELING_BITMASK | CANCELED_BITMASK))
 			   == CANCELING_BITMASK, 0))
     {
-      lll_futex_wait (&self->cancelhandling, newval, LLL_PRIVATE);
+      futex_wait_simple ((unsigned int *) &self->cancelhandling, newval,
+			 FUTEX_PRIVATE);
       newval = THREAD_GETMEM (self, cancelhandling);
     }
 }
diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c
index 8a51161..c043fb5 100644
--- a/nptl/nptl-init.c
+++ b/nptl/nptl-init.c
@@ -34,6 +34,7 @@ 
 #include <shlib-compat.h>
 #include <smp.h>
 #include <lowlevellock.h>
+#include <futex-internal.h>
 #include <kernel-features.h>
 #include <libc-internal.h>
 #include <pthread-pids.h>
@@ -279,10 +280,10 @@  sighandler_setxid (int sig, siginfo_t *si, void *ctx)
 
   /* And release the futex.  */
   self->setxid_futex = 1;
-  lll_futex_wake (&self->setxid_futex, 1, LLL_PRIVATE);
+  futex_wake (&self->setxid_futex, 1, FUTEX_PRIVATE);
 
   if (atomic_decrement_val (&__xidcmd->cntr) == 0)
-    lll_futex_wake (&__xidcmd->cntr, 1, LLL_PRIVATE);
+    futex_wake ((unsigned int *) &__xidcmd->cntr, 1, FUTEX_PRIVATE);
 }
 #endif
 
diff --git a/nptl/pthread_barrier_init.c b/nptl/pthread_barrier_init.c
index 5ea9fad..8fe15ec 100644
--- a/nptl/pthread_barrier_init.c
+++ b/nptl/pthread_barrier_init.c
@@ -36,6 +36,7 @@  __pthread_barrier_init (barrier, attr, count)
 {
   struct pthread_barrier *ibarrier;
 
+  /* XXX EINVAL is not specified by POSIX as a possible error code.  */
   if (__glibc_unlikely (count == 0))
     return EINVAL;
 
@@ -44,11 +45,6 @@  __pthread_barrier_init (barrier, attr, count)
        ? iattr = (struct pthread_barrierattr *) attr
        : &default_barrierattr);
 
-  if (iattr->pshared != PTHREAD_PROCESS_PRIVATE
-      && __builtin_expect (iattr->pshared != PTHREAD_PROCESS_SHARED, 0))
-    /* Invalid attribute.  */
-    return EINVAL;
-
   ibarrier = (struct pthread_barrier *) barrier;
 
   /* Initialize the individual fields.  */
@@ -57,14 +53,10 @@  __pthread_barrier_init (barrier, attr, count)
   ibarrier->init_count = count;
   ibarrier->curr_event = 0;
 
-#ifdef __ASSUME_PRIVATE_FUTEX
+  /* XXX Don't use FUTEX_SHARED or FUTEX_PRIVATE as long as there are still
+     assembly implementations that expect the value determined below.  */
   ibarrier->private = (iattr->pshared != PTHREAD_PROCESS_PRIVATE
 		       ? 0 : FUTEX_PRIVATE_FLAG);
-#else
-  ibarrier->private = (iattr->pshared != PTHREAD_PROCESS_PRIVATE
-		       ? 0 : THREAD_GETMEM (THREAD_SELF,
-					    header.private_futex));
-#endif
 
   return 0;
 }
diff --git a/nptl/pthread_barrier_wait.c b/nptl/pthread_barrier_wait.c
index d69a929..2b34e30 100644
--- a/nptl/pthread_barrier_wait.c
+++ b/nptl/pthread_barrier_wait.c
@@ -19,6 +19,7 @@ 
 #include <errno.h>
 #include <sysdep.h>
 #include <lowlevellock.h>
+#include <futex-internal.h>
 #include <pthreadP.h>
 
 
@@ -29,9 +30,12 @@  __pthread_barrier_wait (barrier)
 {
   struct pthread_barrier *ibarrier = (struct pthread_barrier *) barrier;
   int result = 0;
+  int lll_private = ibarrier->private ^ FUTEX_PRIVATE_FLAG;
+  int futex_private = (lll_private == LLL_PRIVATE
+		       ? FUTEX_PRIVATE : FUTEX_SHARED);
 
   /* Make sure we are alone.  */
-  lll_lock (ibarrier->lock, ibarrier->private ^ FUTEX_PRIVATE_FLAG);
+  lll_lock (ibarrier->lock, lll_private);
 
   /* One more arrival.  */
   --ibarrier->left;
@@ -44,8 +48,7 @@  __pthread_barrier_wait (barrier)
       ++ibarrier->curr_event;
 
       /* Wake up everybody.  */
-      lll_futex_wake (&ibarrier->curr_event, INT_MAX,
-		      ibarrier->private ^ FUTEX_PRIVATE_FLAG);
+      futex_wake (&ibarrier->curr_event, INT_MAX, futex_private);
 
       /* This is the thread which finished the serialization.  */
       result = PTHREAD_BARRIER_SERIAL_THREAD;
@@ -57,12 +60,11 @@  __pthread_barrier_wait (barrier)
       unsigned int event = ibarrier->curr_event;
 
       /* Before suspending, make the barrier available to others.  */
-      lll_unlock (ibarrier->lock, ibarrier->private ^ FUTEX_PRIVATE_FLAG);
+      lll_unlock (ibarrier->lock, lll_private);
 
       /* Wait for the event counter of the barrier to change.  */
       do
-	lll_futex_wait (&ibarrier->curr_event, event,
-			ibarrier->private ^ FUTEX_PRIVATE_FLAG);
+	futex_wait_simple (&ibarrier->curr_event, event, futex_private);
       while (event == ibarrier->curr_event);
     }
 
@@ -72,7 +74,7 @@  __pthread_barrier_wait (barrier)
   /* If this was the last woken thread, unlock.  */
   if (atomic_increment_val (&ibarrier->left) == init_count)
     /* We are done.  */
-    lll_unlock (ibarrier->lock, ibarrier->private ^ FUTEX_PRIVATE_FLAG);
+    lll_unlock (ibarrier->lock, lll_private);
 
   return result;
 }
diff --git a/nptl/pthread_barrierattr_setpshared.c b/nptl/pthread_barrierattr_setpshared.c
index 86d72c5..eeaee5d 100644
--- a/nptl/pthread_barrierattr_setpshared.c
+++ b/nptl/pthread_barrierattr_setpshared.c
@@ -18,6 +18,7 @@ 
 
 #include <errno.h>
 #include "pthreadP.h"
+#include <futex-internal.h>
 
 
 int
@@ -27,9 +28,9 @@  pthread_barrierattr_setpshared (attr, pshared)
 {
   struct pthread_barrierattr *iattr;
 
-  if (pshared != PTHREAD_PROCESS_PRIVATE
-      && __builtin_expect (pshared != PTHREAD_PROCESS_SHARED, 0))
-    return EINVAL;
+  int err = futex_supports_pshared (pshared);
+  if (err != 0)
+    return err;
 
   iattr = (struct pthread_barrierattr *) attr;
 
diff --git a/nptl/pthread_condattr_setpshared.c b/nptl/pthread_condattr_setpshared.c
index 3a760cf..a015403 100644
--- a/nptl/pthread_condattr_setpshared.c
+++ b/nptl/pthread_condattr_setpshared.c
@@ -18,15 +18,16 @@ 
 
 #include <errno.h>
 #include <pthreadP.h>
+#include <futex-internal.h>
 
 int
 pthread_condattr_setpshared (attr, pshared)
      pthread_condattr_t *attr;
      int pshared;
 {
-  if (pshared != PTHREAD_PROCESS_PRIVATE
-      && __builtin_expect (pshared != PTHREAD_PROCESS_SHARED, 0))
-    return EINVAL;
+  int err = futex_supports_pshared (pshared);
+  if (err != 0)
+    return err;
 
   int *valuep = &((struct pthread_condattr *) attr)->value;
 
diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
index 71a5619..d10f4ea 100644
--- a/nptl/pthread_create.c
+++ b/nptl/pthread_create.c
@@ -31,6 +31,7 @@ 
 #include <kernel-features.h>
 #include <exit-thread.h>
 #include <default-sched.h>
+#include <futex-internal.h>
 
 #include <shlib-compat.h>
 
@@ -269,7 +270,7 @@  START_THREAD_DEFN
 
   /* Allow setxid from now onwards.  */
   if (__glibc_unlikely (atomic_exchange_acq (&pd->setxid_futex, 0) == -2))
-    lll_futex_wake (&pd->setxid_futex, 1, LLL_PRIVATE);
+    futex_wake (&pd->setxid_futex, 1, FUTEX_PRIVATE);
 
 #ifdef __NR_set_robust_list
 # ifndef __ASSUME_SET_ROBUST_LIST
@@ -414,7 +415,8 @@  START_THREAD_DEFN
 	  this->__list.__next = NULL;
 
 	  atomic_or (&this->__lock, FUTEX_OWNER_DIED);
-	  lll_futex_wake (&this->__lock, 1, /* XYZ */ LLL_SHARED);
+	  futex_wake ((unsigned int *) &this->__lock, 1,
+		      /* XYZ */ FUTEX_SHARED);
 	}
       while (robust != (void *) &pd->robust_head);
     }
@@ -442,7 +444,11 @@  START_THREAD_DEFN
       /* Some other thread might call any of the setXid functions and expect
 	 us to reply.  In this case wait until we did that.  */
       do
-	lll_futex_wait (&pd->setxid_futex, 0, LLL_PRIVATE);
+	/* XXX This differs from the typical futex_wait_simple pattern in that
+	   the futex_wait condition (setxid_futex) is different from the
+	   condition used in the surrounding loop (cancelhandling).  We need
+	   to check and document why this is correct.  */
+	futex_wait_simple (&pd->setxid_futex, 0, FUTEX_PRIVATE);
       while (pd->cancelhandling & SETXID_BITMASK);
 
       /* Reset the value so that the stack can be reused.  */
@@ -683,7 +689,7 @@  __pthread_create_2_1 (newthread, attr, start_routine, arg)
 	     stillborn thread.  */
 	  if (__glibc_unlikely (atomic_exchange_acq (&pd->setxid_futex, 0)
 				== -2))
-	    lll_futex_wake (&pd->setxid_futex, 1, LLL_PRIVATE);
+	    futex_wake (&pd->setxid_futex, 1, FUTEX_PRIVATE);
 
 	  /* Free the resources.  */
 	  __deallocate_stack (pd);
diff --git a/nptl/pthread_mutexattr_setpshared.c b/nptl/pthread_mutexattr_setpshared.c
index 77ee9f7..62fd168 100644
--- a/nptl/pthread_mutexattr_setpshared.c
+++ b/nptl/pthread_mutexattr_setpshared.c
@@ -18,6 +18,7 @@ 
 
 #include <errno.h>
 #include <pthreadP.h>
+#include <futex-internal.h>
 
 
 int
@@ -27,9 +28,9 @@  pthread_mutexattr_setpshared (attr, pshared)
 {
   struct pthread_mutexattr *iattr;
 
-  if (pshared != PTHREAD_PROCESS_PRIVATE
-      && __builtin_expect (pshared != PTHREAD_PROCESS_SHARED, 0))
-    return EINVAL;
+  int err = futex_supports_pshared (pshared);
+  if (err != 0)
+    return err;
 
   iattr = (struct pthread_mutexattr *) attr;
 
diff --git a/nptl/pthread_once.c b/nptl/pthread_once.c
index fe6d923..3c5bc33 100644
--- a/nptl/pthread_once.c
+++ b/nptl/pthread_once.c
@@ -17,7 +17,7 @@ 
    <http://www.gnu.org/licenses/>.  */
 
 #include "pthreadP.h"
-#include <lowlevellock.h>
+#include <futex-internal.h>
 #include <atomic.h>
 
 
@@ -35,7 +35,7 @@  clear_once_control (void *arg)
      get interrupted (see __pthread_once), so all we need to relay to other
      threads is the state being reset again.  */
   atomic_store_relaxed (once_control, 0);
-  lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE);
+  futex_wake ((unsigned int *) once_control, INT_MAX, FUTEX_PRIVATE);
 }
 
 
@@ -100,8 +100,10 @@  __pthread_once_slow (pthread_once_t *once_control, void (*init_routine) (void))
 	     is set and __PTHREAD_ONCE_DONE is not.  */
 	  if (val == newval)
 	    {
-	      /* Same generation, some other thread was faster. Wait.  */
-	      lll_futex_wait (once_control, newval, LLL_PRIVATE);
+	      /* Same generation, some other thread was faster.  Wait and
+		 retry.  */
+	      futex_wait_simple ((unsigned int *) once_control,
+				 (unsigned int) newval, FUTEX_PRIVATE);
 	      continue;
 	    }
 	}
@@ -122,7 +124,7 @@  __pthread_once_slow (pthread_once_t *once_control, void (*init_routine) (void))
       atomic_store_release (once_control, __PTHREAD_ONCE_DONE);
 
       /* Wake up all other threads.  */
-      lll_futex_wake (once_control, INT_MAX, LLL_PRIVATE);
+      futex_wake ((unsigned int *) once_control, INT_MAX, FUTEX_PRIVATE);
       break;
     }
 
diff --git a/nptl/pthread_rwlock_init.c b/nptl/pthread_rwlock_init.c
index 23ee6c6..99ab5e3 100644
--- a/nptl/pthread_rwlock_init.c
+++ b/nptl/pthread_rwlock_init.c
@@ -58,15 +58,8 @@  __pthread_rwlock_init (rwlock, attr)
 
      If the pshared value is in locking functions XORed with avail
      we get the expected result.  */
-#ifdef __ASSUME_PRIVATE_FUTEX
   rwlock->__data.__shared = (iattr->pshared == PTHREAD_PROCESS_PRIVATE
 			     ? 0 : FUTEX_PRIVATE_FLAG);
-#else
-  rwlock->__data.__shared = (iattr->pshared == PTHREAD_PROCESS_PRIVATE
-			     ? 0
-			     : THREAD_GETMEM (THREAD_SELF,
-					      header.private_futex));
-#endif
 
   return 0;
 }
diff --git a/nptl/pthread_rwlock_rdlock.c b/nptl/pthread_rwlock_rdlock.c
index 004a386..eb7ac8d 100644
--- a/nptl/pthread_rwlock_rdlock.c
+++ b/nptl/pthread_rwlock_rdlock.c
@@ -19,6 +19,7 @@ 
 #include <errno.h>
 #include <sysdep.h>
 #include <lowlevellock.h>
+#include <futex-internal.h>
 #include <pthread.h>
 #include <pthreadP.h>
 #include <stap-probe.h>
@@ -32,6 +33,8 @@  __pthread_rwlock_rdlock_slow (pthread_rwlock_t *rwlock)
 {
   int result = 0;
   bool wake = false;
+  int futex_shared =
+      rwlock->__data.__shared == LLL_PRIVATE ? FUTEX_PRIVATE : FUTEX_SHARED;
 
   /* Lock is taken in caller.  */
 
@@ -60,9 +63,10 @@  __pthread_rwlock_rdlock_slow (pthread_rwlock_t *rwlock)
       /* Free the lock.  */
       lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
 
-      /* Wait for the writer to finish.  */
-      lll_futex_wait (&rwlock->__data.__readers_wakeup, waitval,
-		      rwlock->__data.__shared);
+      /* Wait for the writer to finish.  We do not check the return value
+	 because we decide how to continue based on the state of the rwlock.  */
+      futex_wait_simple (&rwlock->__data.__readers_wakeup, waitval,
+			 futex_shared);
 
       /* Get the lock.  */
       lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
@@ -103,8 +107,7 @@  __pthread_rwlock_rdlock_slow (pthread_rwlock_t *rwlock)
   lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
 
   if (wake)
-    lll_futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX,
-		    rwlock->__data.__shared);
+    futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX, futex_shared);
 
   return result;
 }
@@ -117,6 +120,8 @@  __pthread_rwlock_rdlock (pthread_rwlock_t *rwlock)
 {
   int result = 0;
   bool wake = false;
+  int futex_shared =
+      rwlock->__data.__shared == LLL_PRIVATE ? FUTEX_PRIVATE : FUTEX_SHARED;
 
   LIBC_PROBE (rdlock_entry, 1, rwlock);
 
@@ -164,8 +169,7 @@  __pthread_rwlock_rdlock (pthread_rwlock_t *rwlock)
       lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
 
       if (wake)
-	lll_futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX,
-			rwlock->__data.__shared);
+	futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX, futex_shared);
 
       return result;
     }
diff --git a/nptl/pthread_rwlock_timedrdlock.c b/nptl/pthread_rwlock_timedrdlock.c
index 63fb313..93d235e 100644
--- a/nptl/pthread_rwlock_timedrdlock.c
+++ b/nptl/pthread_rwlock_timedrdlock.c
@@ -19,10 +19,10 @@ 
 #include <errno.h>
 #include <sysdep.h>
 #include <lowlevellock.h>
+#include <futex-internal.h>
 #include <pthread.h>
 #include <pthreadP.h>
 #include <sys/time.h>
-#include <kernel-features.h>
 #include <stdbool.h>
 
 
@@ -34,6 +34,8 @@  pthread_rwlock_timedrdlock (rwlock, abstime)
 {
   int result = 0;
   bool wake = false;
+  int futex_shared =
+      rwlock->__data.__shared == LLL_PRIVATE ? FUTEX_PRIVATE : FUTEX_SHARED;
 
   /* Make sure we are alone.  */
   lll_lock(rwlock->__data.__lock, rwlock->__data.__shared);
@@ -91,38 +93,6 @@  pthread_rwlock_timedrdlock (rwlock, abstime)
 	  break;
 	}
 
-      /* Work around the fact that the kernel rejects negative timeout values
-	 despite them being valid.  */
-      if (__glibc_unlikely (abstime->tv_sec < 0))
-	{
-	  result = ETIMEDOUT;
-	  break;
-	}
-
-#if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
-     || !defined lll_futex_timed_wait_bitset)
-      /* Get the current time.  So far we support only one clock.  */
-      struct timeval tv;
-      (void) __gettimeofday (&tv, NULL);
-
-      /* Convert the absolute timeout value to a relative timeout.  */
-      struct timespec rt;
-      rt.tv_sec = abstime->tv_sec - tv.tv_sec;
-      rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
-      if (rt.tv_nsec < 0)
-	{
-	  rt.tv_nsec += 1000000000;
-	  --rt.tv_sec;
-	}
-      /* Did we already time out?  */
-      if (rt.tv_sec < 0)
-	{
-	  /* Yep, return with an appropriate error.  */
-	  result = ETIMEDOUT;
-	  break;
-	}
-#endif
-
       /* Remember that we are a reader.  */
       if (++rwlock->__data.__nr_readers_queued == 0)
 	{
@@ -137,17 +107,11 @@  pthread_rwlock_timedrdlock (rwlock, abstime)
       /* Free the lock.  */
       lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
 
-      /* Wait for the writer to finish.  */
-#if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
-     || !defined lll_futex_timed_wait_bitset)
-      err = lll_futex_timed_wait (&rwlock->__data.__readers_wakeup,
-				  waitval, &rt, rwlock->__data.__shared);
-#else
-      err = lll_futex_timed_wait_bitset (&rwlock->__data.__readers_wakeup,
-					 waitval, abstime,
-					 FUTEX_CLOCK_REALTIME,
-					 rwlock->__data.__shared);
-#endif
+      /* Wait for the writer to finish.  We handle ETIMEDOUT below; on other
+	 return values, we decide how to continue based on the state of the
+	 rwlock.  */
+      err = futex_abstimed_wait (&rwlock->__data.__readers_wakeup, waitval,
+				 abstime, futex_shared);
 
       /* Get the lock.  */
       lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
@@ -155,7 +119,7 @@  pthread_rwlock_timedrdlock (rwlock, abstime)
       --rwlock->__data.__nr_readers_queued;
 
       /* Did the futex call time out?  */
-      if (err == -ETIMEDOUT)
+      if (err == ETIMEDOUT)
 	{
 	  /* Yep, report it.  */
 	  result = ETIMEDOUT;
@@ -167,8 +131,7 @@  pthread_rwlock_timedrdlock (rwlock, abstime)
   lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
 
   if (wake)
-    lll_futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX,
-		    rwlock->__data.__shared);
+    futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX, futex_shared);
 
   return result;
 }
diff --git a/nptl/pthread_rwlock_timedwrlock.c b/nptl/pthread_rwlock_timedwrlock.c
index c542534..615623a 100644
--- a/nptl/pthread_rwlock_timedwrlock.c
+++ b/nptl/pthread_rwlock_timedwrlock.c
@@ -19,10 +19,10 @@ 
 #include <errno.h>
 #include <sysdep.h>
 #include <lowlevellock.h>
+#include <futex-internal.h>
 #include <pthread.h>
 #include <pthreadP.h>
 #include <sys/time.h>
-#include <kernel-features.h>
 #include <stdbool.h>
 
 
@@ -34,6 +34,8 @@  pthread_rwlock_timedwrlock (rwlock, abstime)
 {
   int result = 0;
   bool wake_readers = false;
+  int futex_shared =
+      rwlock->__data.__shared == LLL_PRIVATE ? FUTEX_PRIVATE : FUTEX_SHARED;
 
   /* Make sure we are alone.  */
   lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
@@ -71,37 +73,6 @@  pthread_rwlock_timedwrlock (rwlock, abstime)
 	  break;
 	}
 
-      /* Work around the fact that the kernel rejects negative timeout values
-	 despite them being valid.  */
-      if (__glibc_unlikely (abstime->tv_sec < 0))
-	{
-	  result = ETIMEDOUT;
-	  break;
-	}
-
-#if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
-     || !defined lll_futex_timed_wait_bitset)
-      /* Get the current time.  So far we support only one clock.  */
-      struct timeval tv;
-      (void) __gettimeofday (&tv, NULL);
-
-      /* Convert the absolute timeout value to a relative timeout.  */
-      struct timespec rt;
-      rt.tv_sec = abstime->tv_sec - tv.tv_sec;
-      rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
-      if (rt.tv_nsec < 0)
-	{
-	  rt.tv_nsec += 1000000000;
-	  --rt.tv_sec;
-	}
-      /* Did we already time out?  */
-      if (rt.tv_sec < 0)
-	{
-	  result = ETIMEDOUT;
-	  break;
-	}
-#endif
-
       /* Remember that we are a writer.  */
       if (++rwlock->__data.__nr_writers_queued == 0)
 	{
@@ -116,17 +87,11 @@  pthread_rwlock_timedwrlock (rwlock, abstime)
       /* Free the lock.  */
       lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
 
-      /* Wait for the writer or reader(s) to finish.  */
-#if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
-     || !defined lll_futex_timed_wait_bitset)
-      err = lll_futex_timed_wait (&rwlock->__data.__writer_wakeup,
-				  waitval, &rt, rwlock->__data.__shared);
-#else
-      err = lll_futex_timed_wait_bitset (&rwlock->__data.__writer_wakeup,
-					 waitval, abstime,
-					 FUTEX_CLOCK_REALTIME,
-					 rwlock->__data.__shared);
-#endif
+      /* Wait for the writer or reader(s) to finish.  We handle ETIMEDOUT
+	 below; on other return values, we decide how to continue based on
+	 the state of the rwlock.  */
+      err = futex_abstimed_wait (&rwlock->__data.__writer_wakeup, waitval,
+				 abstime, futex_shared);
 
       /* Get the lock.  */
       lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
@@ -135,7 +100,7 @@  pthread_rwlock_timedwrlock (rwlock, abstime)
       --rwlock->__data.__nr_writers_queued;
 
       /* Did the futex call time out?  */
-      if (err == -ETIMEDOUT)
+      if (err == ETIMEDOUT)
 	{
 	  result = ETIMEDOUT;
 	  /* If we prefer writers, it can have happened that readers blocked
@@ -166,8 +131,7 @@  pthread_rwlock_timedwrlock (rwlock, abstime)
 
   /* Might be required after timeouts.  */
   if (wake_readers)
-    lll_futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX,
-	rwlock->__data.__shared);
+    futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX, futex_shared);
 
   return result;
 }
diff --git a/nptl/pthread_rwlock_tryrdlock.c b/nptl/pthread_rwlock_tryrdlock.c
index cde123f..256188a 100644
--- a/nptl/pthread_rwlock_tryrdlock.c
+++ b/nptl/pthread_rwlock_tryrdlock.c
@@ -19,6 +19,7 @@ 
 #include <errno.h>
 #include "pthreadP.h"
 #include <lowlevellock.h>
+#include <futex-internal.h>
 #include <elide.h>
 #include <stdbool.h>
 
@@ -28,6 +29,8 @@  __pthread_rwlock_tryrdlock (pthread_rwlock_t *rwlock)
 {
   int result = EBUSY;
   bool wake = false;
+  int futex_shared =
+      rwlock->__data.__shared == LLL_PRIVATE ? FUTEX_PRIVATE : FUTEX_SHARED;
 
   if (ELIDE_TRYLOCK (rwlock->__data.__rwelision,
 		     rwlock->__data.__lock == 0
@@ -63,8 +66,7 @@  __pthread_rwlock_tryrdlock (pthread_rwlock_t *rwlock)
   lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
 
   if (wake)
-    lll_futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX,
-		    rwlock->__data.__shared);
+    futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX, futex_shared);
 
   return result;
 }
diff --git a/nptl/pthread_rwlock_unlock.c b/nptl/pthread_rwlock_unlock.c
index d2ad4b0..bdd115d 100644
--- a/nptl/pthread_rwlock_unlock.c
+++ b/nptl/pthread_rwlock_unlock.c
@@ -19,6 +19,7 @@ 
 #include <errno.h>
 #include <sysdep.h>
 #include <lowlevellock.h>
+#include <futex-internal.h>
 #include <pthread.h>
 #include <pthreadP.h>
 #include <stap-probe.h>
@@ -29,6 +30,9 @@ 
 int
 __pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
 {
+  int futex_shared =
+      rwlock->__data.__shared == LLL_PRIVATE ? FUTEX_PRIVATE : FUTEX_SHARED;
+
   LIBC_PROBE (rwlock_unlock, 1, rwlock);
 
   if (ELIDE_UNLOCK (rwlock->__data.__writer == 0
@@ -51,16 +55,15 @@  __pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
 	{
 	  ++rwlock->__data.__writer_wakeup;
 	  lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
-	  lll_futex_wake (&rwlock->__data.__writer_wakeup, 1,
-			  rwlock->__data.__shared);
+	  futex_wake (&rwlock->__data.__writer_wakeup, 1, futex_shared);
 	  return 0;
 	}
       else if (rwlock->__data.__nr_readers_queued)
 	{
 	  ++rwlock->__data.__readers_wakeup;
 	  lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
-	  lll_futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX,
-			  rwlock->__data.__shared);
+	  futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX,
+		      futex_shared);
 	  return 0;
 	}
     }
diff --git a/nptl/pthread_rwlock_wrlock.c b/nptl/pthread_rwlock_wrlock.c
index 835a62f..60fa909 100644
--- a/nptl/pthread_rwlock_wrlock.c
+++ b/nptl/pthread_rwlock_wrlock.c
@@ -19,6 +19,7 @@ 
 #include <errno.h>
 #include <sysdep.h>
 #include <lowlevellock.h>
+#include <futex-internal.h>
 #include <pthread.h>
 #include <pthreadP.h>
 #include <stap-probe.h>
@@ -30,6 +31,8 @@  static int __attribute__((noinline))
 __pthread_rwlock_wrlock_slow (pthread_rwlock_t *rwlock)
 {
   int result = 0;
+  int futex_shared =
+      rwlock->__data.__shared == LLL_PRIVATE ? FUTEX_PRIVATE : FUTEX_SHARED;
 
   /* Caller has taken the lock.  */
 
@@ -58,9 +61,11 @@  __pthread_rwlock_wrlock_slow (pthread_rwlock_t *rwlock)
       /* Free the lock.  */
       lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
 
-      /* Wait for the writer or reader(s) to finish.  */
-      lll_futex_wait (&rwlock->__data.__writer_wakeup, waitval,
-		      rwlock->__data.__shared);
+      /* Wait for the writer or reader(s) to finish.  We do not check the
+	 return value because we decide how to continue based on the state of
+	 the rwlock.  */
+      futex_wait_simple (&rwlock->__data.__writer_wakeup, waitval,
+			 futex_shared);
 
       /* Get the lock.  */
       lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
diff --git a/nptl/pthread_rwlockattr_setpshared.c b/nptl/pthread_rwlockattr_setpshared.c
index 4b4b310..0369209 100644
--- a/nptl/pthread_rwlockattr_setpshared.c
+++ b/nptl/pthread_rwlockattr_setpshared.c
@@ -18,6 +18,7 @@ 
 
 #include <errno.h>
 #include "pthreadP.h"
+#include <futex-internal.h>
 
 
 int
@@ -27,9 +28,9 @@  pthread_rwlockattr_setpshared (attr, pshared)
 {
   struct pthread_rwlockattr *iattr;
 
-  if (pshared != PTHREAD_PROCESS_SHARED
-      && __builtin_expect (pshared != PTHREAD_PROCESS_PRIVATE, 0))
-    return EINVAL;
+  int err = futex_supports_pshared (pshared);
+  if (err != 0)
+    return err;
 
   iattr = (struct pthread_rwlockattr *) attr;
 
diff --git a/nptl/sem_init.c b/nptl/sem_init.c
index 575b661..bd1b592 100644
--- a/nptl/sem_init.c
+++ b/nptl/sem_init.c
@@ -21,22 +21,7 @@ 
 #include <shlib-compat.h>
 #include "semaphoreP.h"
 #include <kernel-features.h>
-
-/* Returns FUTEX_PRIVATE if pshared is zero and private futexes are supported;
-   returns FUTEX_SHARED otherwise.
-   TODO Remove when cleaning up the futex API throughout glibc.  */
-static __always_inline int
-futex_private_if_supported (int pshared)
-{
-  if (pshared != 0)
-    return LLL_SHARED;
-#ifdef __ASSUME_PRIVATE_FUTEX
-  return LLL_PRIVATE;
-#else
-  return THREAD_GETMEM (THREAD_SELF, header.private_futex)
-      ^ FUTEX_PRIVATE_FLAG;
-#endif
-}
+#include <futex-internal.h>
 
 
 int
@@ -48,6 +33,13 @@  __new_sem_init (sem_t *sem, int pshared, unsigned int value)
       __set_errno (EINVAL);
       return -1;
     }
+  pshared = pshared != 0 ? PTHREAD_PROCESS_SHARED : PTHREAD_PROCESS_PRIVATE;
+  int err = futex_supports_pshared (pshared);
+  if (err != 0)
+    {
+      __set_errno (err);
+      return -1;
+    }
 
   /* Map to the internal type.  */
   struct new_sem *isem = (struct new_sem *) sem;
@@ -60,7 +52,8 @@  __new_sem_init (sem_t *sem, int pshared, unsigned int value)
   isem->nwaiters = 0;
 #endif
 
-  isem->private = futex_private_if_supported (pshared);
+  isem->private = (pshared == PTHREAD_PROCESS_PRIVATE
+		   ? FUTEX_PRIVATE : FUTEX_SHARED);
 
   return 0;
 }
diff --git a/nptl/sem_open.c b/nptl/sem_open.c
index ecd051a..5ee8b71 100644
--- a/nptl/sem_open.c
+++ b/nptl/sem_open.c
@@ -30,6 +30,7 @@ 
 #include <sys/stat.h>
 #include "semaphoreP.h"
 #include <shm-directory.h>
+#include <futex-internal.h>
 
 
 /* Comparison function for search of existing mapping.  */
@@ -141,6 +142,14 @@  sem_open (const char *name, int oflag, ...)
   int fd;
   sem_t *result;
 
+  /* Check that shared futexes are supported.  */
+  int err = futex_supports_pshared (PTHREAD_PROCESS_SHARED);
+  if (err != 0)
+    {
+      __set_errno (err);
+      return SEM_FAILED;
+    }
+
   /* Create the name of the final file in local variable SHM_NAME.  */
   SHM_GET_NAME (EINVAL, SEM_FAILED, SEM_SHM_PREFIX);
 
@@ -201,7 +210,7 @@  sem_open (const char *name, int oflag, ...)
       sem.newsem.nwaiters = 0;
 #endif
       /* This always is a shared semaphore.  */
-      sem.newsem.private = LLL_SHARED;
+      sem.newsem.private = FUTEX_SHARED;
 
       /* Initialize the remaining bytes as well.  */
       memset ((char *) &sem.initsem + sizeof (struct new_sem), '\0',
diff --git a/nptl/sem_post.c b/nptl/sem_post.c
index b6d30b5..06d8359 100644
--- a/nptl/sem_post.c
+++ b/nptl/sem_post.c
@@ -20,37 +20,13 @@ 
 #include <atomic.h>
 #include <errno.h>
 #include <sysdep.h>
-#include <lowlevellock.h>
+#include <lowlevellock.h>	/* lll_futex* used by the old code.  */
+#include <futex-internal.h>
 #include <internaltypes.h>
 #include <semaphore.h>
 
 #include <shlib-compat.h>
 
-/* Wrapper for lll_futex_wake, with error checking.
-   TODO Remove when cleaning up the futex API throughout glibc.  */
-static __always_inline void
-futex_wake (unsigned int* futex, int processes_to_wake, int private)
-{
-  int res = lll_futex_wake (futex, processes_to_wake, private);
-  /* No error.  Ignore the number of woken processes.  */
-  if (res >= 0)
-    return;
-  switch (res)
-    {
-    case -EFAULT: /* Could have happened due to memory reuse.  */
-    case -EINVAL: /* Could be either due to incorrect alignment (a bug in
-		     glibc or in the application) or due to memory being
-		     reused for a PI futex.  We cannot distinguish between the
-		     two causes, and one of them is correct use, so we do not
-		     act in this case.  */
-      return;
-    case -ENOSYS: /* Must have been caused by a glibc bug.  */
-    /* No other errors are documented at this time.  */
-    default:
-      abort ();
-    }
-}
-
 
 /* See sem_wait for an explanation of the algorithm.  */
 int
diff --git a/nptl/sem_wait.c b/nptl/sem_wait.c
index c1fd10c..fce7ed4 100644
--- a/nptl/sem_wait.c
+++ b/nptl/sem_wait.c
@@ -17,6 +17,7 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#include <lowlevellock.h>	/* lll_futex* used by the old code.  */
 #include "sem_waitcommon.c"
 
 int
diff --git a/nptl/sem_waitcommon.c b/nptl/sem_waitcommon.c
index 772425d..d3702c7 100644
--- a/nptl/sem_waitcommon.c
+++ b/nptl/sem_waitcommon.c
@@ -20,7 +20,7 @@ 
 #include <kernel-features.h>
 #include <errno.h>
 #include <sysdep.h>
-#include <lowlevellock.h>
+#include <futex-internal.h>
 #include <internaltypes.h>
 #include <semaphore.h>
 #include <sys/time.h>
@@ -29,110 +29,6 @@ 
 #include <shlib-compat.h>
 #include <atomic.h>
 
-/* Wrapper for lll_futex_wait with absolute timeout and error checking.
-   TODO Remove when cleaning up the futex API throughout glibc.  */
-static __always_inline int
-futex_abstimed_wait (unsigned int* futex, unsigned int expected,
-		     const struct timespec* abstime, int private, bool cancel)
-{
-  int err, oldtype;
-  if (abstime == NULL)
-    {
-      if (cancel)
-	oldtype = __pthread_enable_asynccancel ();
-      err = lll_futex_wait (futex, expected, private);
-      if (cancel)
-	__pthread_disable_asynccancel (oldtype);
-    }
-  else
-    {
-#if (defined __ASSUME_FUTEX_CLOCK_REALTIME	\
-     && defined lll_futex_timed_wait_bitset)
-      /* The Linux kernel returns EINVAL for this, but in userspace
-	 such a value is valid.  */
-      if (abstime->tv_sec < 0)
-	return ETIMEDOUT;
-#else
-      struct timeval tv;
-      struct timespec rt;
-      int sec, nsec;
-
-      /* Get the current time.  */
-      __gettimeofday (&tv, NULL);
-
-      /* Compute relative timeout.  */
-      sec = abstime->tv_sec - tv.tv_sec;
-      nsec = abstime->tv_nsec - tv.tv_usec * 1000;
-      if (nsec < 0)
-        {
-          nsec += 1000000000;
-          --sec;
-        }
-
-      /* Already timed out?  */
-      if (sec < 0)
-        return ETIMEDOUT;
-
-      /* Do wait.  */
-      rt.tv_sec = sec;
-      rt.tv_nsec = nsec;
-#endif
-      if (cancel)
-	oldtype = __pthread_enable_asynccancel ();
-#if (defined __ASSUME_FUTEX_CLOCK_REALTIME	\
-     && defined lll_futex_timed_wait_bitset)
-      err = lll_futex_timed_wait_bitset (futex, expected, abstime,
-					 FUTEX_CLOCK_REALTIME, private);
-#else
-      err = lll_futex_timed_wait (futex, expected, &rt, private);
-#endif
-      if (cancel)
-	__pthread_disable_asynccancel (oldtype);
-    }
-  switch (err)
-    {
-    case 0:
-    case -EAGAIN:
-    case -EINTR:
-    case -ETIMEDOUT:
-      return -err;
-
-    case -EFAULT: /* Must have been caused by a glibc or application bug.  */
-    case -EINVAL: /* Either due to wrong alignment or due to the timeout not
-		     being normalized.  Must have been caused by a glibc or
-		     application bug.  */
-    case -ENOSYS: /* Must have been caused by a glibc bug.  */
-    /* No other errors are documented at this time.  */
-    default:
-      abort ();
-    }
-}
-
-/* Wrapper for lll_futex_wake, with error checking.
-   TODO Remove when cleaning up the futex API throughout glibc.  */
-static __always_inline void
-futex_wake (unsigned int* futex, int processes_to_wake, int private)
-{
-  int res = lll_futex_wake (futex, processes_to_wake, private);
-  /* No error.  Ignore the number of woken processes.  */
-  if (res >= 0)
-    return;
-  switch (res)
-    {
-    case -EFAULT: /* Could have happened due to memory reuse.  */
-    case -EINVAL: /* Could be either due to incorrect alignment (a bug in
-		     glibc or in the application) or due to memory being
-		     reused for a PI futex.  We cannot distinguish between the
-		     two causes, and one of them is correct use, so we do not
-		     act in this case.  */
-      return;
-    case -ENOSYS: /* Must have been caused by a glibc bug.  */
-    /* No other errors are documented at this time.  */
-    default:
-      abort ();
-    }
-}
-
 
 /* The semaphore provides two main operations: sem_post adds a token to the
    semaphore; sem_wait grabs a token from the semaphore, potentially waiting
@@ -220,11 +116,12 @@  do_futex_wait (struct new_sem *sem, const struct timespec *abstime)
   int err;
 
 #if __HAVE_64B_ATOMICS
-  err = futex_abstimed_wait ((unsigned int *) &sem->data + SEM_VALUE_OFFSET, 0,
-			     abstime, sem->private, true);
+  err = futex_abstimed_wait_cancelable (
+      (unsigned int *) &sem->data + SEM_VALUE_OFFSET, 0, abstime,
+      sem->private);
 #else
-  err = futex_abstimed_wait (&sem->value, SEM_NWAITERS_MASK, abstime,
-			     sem->private, true);
+  err = futex_abstimed_wait_cancelable (&sem->value, SEM_NWAITERS_MASK,
+					abstime, sem->private);
 #endif
 
   return err;
diff --git a/nptl/unregister-atfork.c b/nptl/unregister-atfork.c
index 3838cb7..6d08ed7 100644
--- a/nptl/unregister-atfork.c
+++ b/nptl/unregister-atfork.c
@@ -20,6 +20,7 @@ 
 #include <stdlib.h>
 #include <fork.h>
 #include <atomic.h>
+#include <futex-internal.h>
 
 
 void
@@ -114,7 +115,7 @@  __unregister_atfork (dso_handle)
       atomic_decrement (&deleted->handler->refcntr);
       unsigned int val;
       while ((val = deleted->handler->refcntr) != 0)
-	lll_futex_wait (&deleted->handler->refcntr, val, LLL_PRIVATE);
+	futex_wait_simple (&deleted->handler->refcntr, val, FUTEX_PRIVATE);
 
       deleted = deleted->next;
     }
diff --git a/sysdeps/nacl/exit-thread.h b/sysdeps/nacl/exit-thread.h
index c809405..915f93d 100644
--- a/sysdeps/nacl/exit-thread.h
+++ b/sysdeps/nacl/exit-thread.h
@@ -18,7 +18,7 @@ 
 
 #include <assert.h>
 #include <atomic.h>
-#include <lowlevellock.h>
+#include <futex-internal.h>
 #include <nacl-interfaces.h>
 #include <nptl/pthreadP.h>
 
@@ -64,7 +64,7 @@  __exit_thread (void)
       assert (NACL_EXITING_TID > 0);
 
       atomic_store_relaxed (&pd->tid, NACL_EXITING_TID);
-      lll_futex_wake (&pd->tid, 1, LLL_PRIVATE);
+      futex_wake ((unsigned int *) &pd->tid, 1, FUTEX_PRIVATE);
     }
 
   /* This clears PD->tid some time after the thread stack can never
diff --git a/sysdeps/nacl/futex-internal.h b/sysdeps/nacl/futex-internal.h
new file mode 100644
index 0000000..593bb9d
--- /dev/null
+++ b/sysdeps/nacl/futex-internal.h
@@ -0,0 +1,248 @@ 
+/* futex operations for glibc-internal use.  NaCl version.
+   Copyright (C) 2014-2015 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef FUTEX_INTERNAL_H
+#define FUTEX_INTERNAL_H
+
+#include <sysdeps/nptl/futex-internal.h>
+#include <errno.h>
+#include <lowlevellock-futex.h>
+#include <nacl-interfaces.h>
+#include <nptl/pthreadP.h>
+
+/* See sysdeps/nptl/futex-internal.h for documentation; this file only
+   contains NaCl-specific comments.
+
+   There is no support yet for shared futexes nor for exact relative
+   timeouts.  */
+
+/* See sysdeps/nptl/futex-internal.h for constraints on the value of the
+   FUTEX_PRIVATE and FUTEX_SHARED constants.
+   Shared futexes are not yet supported, and we never allow clients to
+   actually request shared futexes.  Therefore, we do not need a different
+   value.  */
+#undef FUTEX_SHARED
+#define FUTEX_SHARED  FUTEX_PRIVATE
+
+/* FUTEX_SHARED is not yet supported.  */
+static __always_inline int
+futex_supports_pshared (int pshared)
+{
+  if (__glibc_likely (pshared == PTHREAD_PROCESS_PRIVATE))
+    return 0;
+  else if (pshared == PTHREAD_PROCESS_SHARED)
+    return ENOTSUP;
+  else
+    return EINVAL;
+}
+
+/* Relative timeouts are only emulated via absolute timeouts using the
+   system clock.  */
+static __always_inline bool
+futex_supports_exact_relative_timeouts (void)
+{
+  return false;
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_wait (unsigned int *futex_word, unsigned int expected, int private)
+{
+  int err = lll_futex_timed_wait (futex_word, expected, NULL, private);
+  switch (err)
+    {
+    case 0:
+    case -EAGAIN:
+    case -EINTR:
+      return -err;
+
+    case -ETIMEDOUT: /* Cannot have happened as we provided no timeout.  */
+    case -EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case -EINVAL: /* Either due to wrong alignment or due to the timeout not
+		     being normalized.  Must have been caused by a glibc or
+		     application bug.  */
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_wait_cancelable (unsigned int *futex_word, unsigned int expected,
+		       int private)
+{
+  int oldtype;
+  oldtype = __pthread_enable_asynccancel ();
+  int err = lll_futex_timed_wait (futex_word, expected, NULL, private);
+  __pthread_disable_asynccancel (oldtype);
+  switch (err)
+    {
+    case 0:
+    case -EAGAIN:
+    case -EINTR:
+      return -err;
+
+    case -ETIMEDOUT: /* Cannot have happened as we provided no timeout.  */
+    case -EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case -EINVAL: /* Either due to wrong alignment or due to the timeout not
+		     being normalized.  Must have been caused by a glibc or
+		     application bug.  */
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_reltimed_wait (unsigned int *futex_word, unsigned int expected,
+		     const struct timespec *reltime, int private)
+{
+  int err = lll_futex_timed_wait (futex_word, expected, reltime, private);
+  switch (err)
+    {
+    case 0:
+    case -EAGAIN:
+    case -EINTR:
+    case -ETIMEDOUT:
+      return -err;
+
+    case -EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case -EINVAL: /* Either due to wrong alignment or due to the timeout not
+		     being normalized.  Must have been caused by a glibc or
+		     application bug.  */
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_reltimed_wait_cancelable (unsigned int *futex_word,
+				unsigned int expected,
+			        const struct timespec *reltime, int private)
+{
+  int oldtype;
+  oldtype = __pthread_enable_asynccancel ();
+  int err = lll_futex_timed_wait (futex_word, expected, reltime, private);
+  __pthread_disable_asynccancel (oldtype);
+  switch (err)
+    {
+    case 0:
+    case -EAGAIN:
+    case -EINTR:
+    case -ETIMEDOUT:
+      return -err;
+
+    case -EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case -EINVAL: /* Either due to wrong alignment or due to the timeout not
+		     being normalized.  Must have been caused by a glibc or
+		     application bug.  */
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_abstimed_wait (unsigned int *futex_word, unsigned int expected,
+		     const struct timespec *abstime, int private)
+{
+  int err = __nacl_irt_futex.futex_wait_abs ((volatile int *) futex_word,
+					     expected, abstime);
+  switch (err)
+    {
+    case 0:
+    case EAGAIN:
+    case EINTR:
+    case ETIMEDOUT:
+      return err;
+
+    case EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case EINVAL: /* Either due to wrong alignment or due to the timeout not
+		    being normalized.  Must have been caused by a glibc or
+		    application bug.  */
+    case ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_abstimed_wait_cancelable (unsigned int *futex_word,
+				unsigned int expected,
+			        const struct timespec *abstime, int private)
+{
+  int oldtype;
+  oldtype = __pthread_enable_asynccancel ();
+  int err = __nacl_irt_futex.futex_wait_abs ((volatile int *) futex_word,
+					     expected, abstime);
+  __pthread_disable_asynccancel (oldtype);
+  switch (err)
+    {
+    case 0:
+    case EAGAIN:
+    case EINTR:
+    case ETIMEDOUT:
+      return err;
+
+    case EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case EINVAL: /* Either due to wrong alignment or due to the timeout not
+		    being normalized.  Must have been caused by a glibc or
+		    application bug.  */
+    case ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline void
+futex_wake (unsigned int *futex_word, int processes_to_wake, int private)
+{
+  int res = lll_futex_wake (futex_word, processes_to_wake, private);
+  /* No error.  Ignore the number of woken processes.  */
+  if (res >= 0)
+    return;
+  switch (res)
+    {
+    case -EFAULT: /* Could have happened due to memory reuse.  */
+    case -EINVAL: /* Could be either due to incorrect alignment (a bug in
+		     glibc or in the application) or due to memory being
+		     reused for a PI futex.  We cannot distinguish between the
+		     two causes, and one of them is correct use, so we do not
+		     act in this case.  */
+      return;
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+#endif  /* futex-internal.h */
diff --git a/sysdeps/nptl/aio_misc.h b/sysdeps/nptl/aio_misc.h
index d5d1c08..4a6ebfc 100644
--- a/sysdeps/nptl/aio_misc.h
+++ b/sysdeps/nptl/aio_misc.h
@@ -22,14 +22,14 @@ 
 
 #include <assert.h>
 #include <nptl/pthreadP.h>
-#include <lowlevellock.h>
+#include <futex-internal.h>
 
 #define DONT_NEED_AIO_MISC_COND	1
 
 #define AIO_MISC_NOTIFY(waitlist) \
   do {									      \
     if (*waitlist->counterp > 0 && --*waitlist->counterp == 0)		      \
-      lll_futex_wake (waitlist->counterp, 1, LLL_PRIVATE);		      \
+      futex_wake ((unsigned int *) waitlist->counterp, 1, FUTEX_PRIVATE);     \
   } while (0)
 
 #define AIO_MISC_WAIT(result, futex, timeout, cancel)			      \
@@ -48,9 +48,9 @@ 
 	int status;							      \
 	do								      \
 	  {								      \
-	    status = lll_futex_timed_wait (futexaddr, oldval, timeout,	      \
-					   LLL_PRIVATE);		      \
-	    if (status != -EWOULDBLOCK)					      \
+	    status = futex_reltimed_wait ((unsigned int *) futexaddr, oldval, \
+					  timeout, FUTEX_PRIVATE);	      \
+	    if (status != EAGAIN)					      \
 	      break;							      \
 									      \
 	    oldval = *futexaddr;					      \
@@ -60,12 +60,12 @@ 
 	if (cancel)							      \
 	  LIBC_CANCEL_RESET (oldtype);					      \
 									      \
-	if (status == -EINTR)						      \
+	if (status == EINTR)						      \
 	  result = EINTR;						      \
-	else if (status == -ETIMEDOUT)					      \
+	else if (status == ETIMEDOUT)					      \
 	  result = EAGAIN;						      \
 	else								      \
-	  assert (status == 0 || status == -EWOULDBLOCK);		      \
+	  assert (status == 0 || status == EAGAIN);			      \
 									      \
 	pthread_mutex_lock (&__aio_requests_mutex);			      \
       }									      \
diff --git a/sysdeps/nptl/fork.c b/sysdeps/nptl/fork.c
index 74482b7..2b9ae4b 100644
--- a/sysdeps/nptl/fork.c
+++ b/sysdeps/nptl/fork.c
@@ -30,6 +30,7 @@ 
 #include <nptl/pthreadP.h>
 #include <fork.h>
 #include <arch-fork.h>
+#include <futex-internal.h>
 
 
 static void
@@ -219,7 +220,7 @@  __libc_fork (void)
 
 	  if (atomic_decrement_and_test (&allp->handler->refcntr)
 	      && allp->handler->need_signal)
-	    lll_futex_wake (&allp->handler->refcntr, 1, LLL_PRIVATE);
+	    futex_wake (&allp->handler->refcntr, 1, FUTEX_PRIVATE);
 
 	  allp = allp->next;
 	}
diff --git a/sysdeps/nptl/futex-internal.h b/sysdeps/nptl/futex-internal.h
new file mode 100644
index 0000000..4f8c8fe
--- /dev/null
+++ b/sysdeps/nptl/futex-internal.h
@@ -0,0 +1,203 @@ 
+/* futex operations for glibc-internal use.  Stub version; do not include
+   this file directly.
+   Copyright (C) 2014-2015 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef STUB_FUTEX_INTERNAL_H
+#define STUB_FUTEX_INTERNAL_H
+
+#include <sys/time.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <libc-internal.h>
+
+/* This file defines futex operations used internally in glibc.  A futex
+   consists of the so-called futex word in userspace, which is of type
+   unsigned int and represents an application-specific condition, and kernel
+   state associated with this particular futex word (e.g., wait queues).  The
+   futex operations we provide are wrappers for the futex syscalls and add
+   glibc-specific error checking of the syscall return value.  We abort on
+   error codes that are caused by bugs in glibc or in the calling application,
+   or when an error code is not known.  We return error codes that can arise
+   in correct executions to the caller.  Each operation calls out exactly the
+   return values that callers need to handle.
+
+   The private flag must be either FUTEX_PRIVATE or FUTEX_SHARED.
+   FUTEX_PRIVATE is always supported, and the implementation can internally
+   use FUTEX_SHARED when FUTEX_PRIVATE is requested.  FUTEX_SHARED is not
+   necessarily supported (use futex_supports_pshared to detect this).
+
+   We expect callers to only use these operations if futexes and the
+   specific futex operations being used are supported (e.g., FUTEX_SHARED).
+
+   Given that waking other threads waiting on a futex involves concurrent
+   accesses to the futex word, you must use atomic operations to access the
+   futex word.
+
+   Both absolute and relative timeouts can be used.  An absolute timeout
+   expires when the given specific point in time on the CLOCK_REALTIME clock
+   passes, or when it already has passed.  A relative timeout expires when
+   the given duration of time on the CLOCK_MONOTONIC clock passes.  Relative
+   timeouts may be imprecise (see futex_supports_exact_relative_timeouts).
+
+   Due to POSIX requirements on when synchronization data structures such
+   as mutexes or semaphores can be destroyed and due to the futex design
+   having separate fast/slow paths for wake-ups, we need to consider that
+   futex_wake calls might effectively target a data structure that has been
+   destroyed and reused for another object, or unmapped; thus, some
+   errors or spurious wake-ups can happen in correct executions that would
+   not be possible in a program using just a single futex whose lifetime
+   does not end before the program terminates.  For background, see:
+   https://sourceware.org/ml/libc-alpha/2014-04/msg00075.html
+   https://lkml.org/lkml/2014/11/27/472  */
+
+/* Defined this way for interoperability with lowlevellock.
+   FUTEX_PRIVATE must be zero because the initializers for pthread_mutex_t,
+   pthread_rwlock_t, and pthread_cond_t initialize the respective field of
+   those structures to zero, and we want FUTEX_PRIVATE to be the default.  */
+#define FUTEX_PRIVATE LLL_PRIVATE
+#define FUTEX_SHARED  LLL_SHARED
+#if FUTEX_PRIVATE != 0
+# error FUTEX_PRIVATE must be equal to 0
+#endif
+
+/* Returns EINVAL if PSHARED is neither PTHREAD_PROCESS_PRIVATE nor
+   PTHREAD_PROCESS_SHARED; otherwise, returns 0 if PSHARED is supported, and
+   ENOTSUP if not.  */
+static __always_inline int
+futex_supports_pshared (int pshared);
+
+/* Returns true if relative timeouts are robust to concurrent changes to the
+   system clock.  If this returns false, relative timeouts can still be used
+   but might be effectively longer or shorter than requested.  */
+static __always_inline bool
+futex_supports_exact_relative_timeouts (void);
+
+/* Atomically wrt other futex operations on the same futex, this blocks iff
+   the value *FUTEX_WORD matches the expected value.  This is
+   semantically equivalent to:
+     l = <get lock associated with futex> (FUTEX_WORD);
+     wait_flag = <get wait_flag associated with futex> (FUTEX_WORD);
+     lock (l);
+     val = atomic_load_relaxed (FUTEX_WORD);
+     if (val != expected) { unlock (l); return EAGAIN; }
+     atomic_store_relaxed (wait_flag, true);
+     unlock (l);
+     // Now block; can time out in futex_time_wait (see below)
+     while (atomic_load_relaxed(wait_flag) && !<spurious wake-up>);
+
+   Note that no guarantee of a happens-before relation between a woken
+   futex_wait and a futex_wake is documented; however, this does not matter
+   in practice because we have to consider spurious wake-ups (see below),
+   and thus would not be able to reliably reason about which futex_wake woke
+   us.
+
+   Returns 0 if woken by a futex operation or spuriously.  (Note that due to
+   the POSIX requirements mentioned above, we need to conservatively assume
+   that unrelated futex_wake operations could wake this futex; it is easiest
+   to just be prepared for spurious wake-ups.)
+   Returns EAGAIN if the futex word did not match the expected value.
+   Returns EINTR if waiting was interrupted by a signal.
+
+   Note that some previous code in glibc assumed the underlying futex
+   operation (e.g., syscall) to start with or include the equivalent of a
+   seq_cst fence; this allows one to avoid an explicit seq_cst fence before
+   a futex_wait call when synchronizing similar to Dekker synchronization.
+   However, we make no such guarantee here.  */
+static __always_inline int
+futex_wait (unsigned int *futex_word, unsigned int expected, int private);
+
+/* Like futex_wait but does not provide any indication why we stopped waiting.
+   Thus, when this function returns, you have to always check FUTEX_WORD to
+   determine whether you need to continue waiting, and you cannot detect
+   whether the waiting was interrupted by a signal.  Example use:
+     while (atomic_load_relaxed (&futex_word) == 23)
+       futex_wait_simple (&futex_word, 23, FUTEX_PRIVATE);
+   This is common enough to make providing this wrapper worthwhile.  */
+static __always_inline void
+futex_wait_simple (unsigned int *futex_word, unsigned int expected,
+		   int private)
+{
+  ignore_value (futex_wait (futex_word, expected, private));
+}
+
+
+/* Like futex_wait but is a POSIX cancellation point.  */
+static __always_inline int
+futex_wait_cancelable (unsigned int *futex_word, unsigned int expected,
+		       int private);
+
+/* Like futex_wait, but will eventually time out (i.e., stop being
+   blocked) after the duration of time provided (i.e., RELTIME) has
+   passed.  The caller must provide a normalized RELTIME.  RELTIME can also
+   equal NULL, in which case this function behaves equivalent to futex_wait.
+
+   Returns the same values as futex_wait under those same conditions;
+   additionally, returns ETIMEDOUT if the timeout expired.
+   */
+static __always_inline int
+futex_reltimed_wait (unsigned int* futex_word, unsigned int expected,
+		     const struct timespec* reltime, int private);
+
+/* Like futex_reltimed_wait but is a POSIX cancellation point.  */
+static __always_inline int
+futex_reltimed_wait_cancelable (unsigned int* futex_word,
+				unsigned int expected,
+			        const struct timespec* reltime, int private);
+
+/* Like futex_reltimed_wait, but the provided timeout (ABSTIME) is an
+   absolute point in time; a call will time out after this point in time.  */
+static __always_inline int
+futex_abstimed_wait (unsigned int* futex_word, unsigned int expected,
+		     const struct timespec* abstime, int private);
+
+/* Like futex_reltimed_wait but is a POSIX cancellation point.  */
+static __always_inline int
+futex_abstimed_wait_cancelable (unsigned int* futex_word,
+				unsigned int expected,
+			        const struct timespec* abstime, int private);
+
+/* Atomically wrt other futex operations on the same futex, this unblocks the
+   specified number of processes, or all processes blocked on this futex if
+   there are fewer than the specified number.  Semantically, this is
+   equivalent to:
+     l = <get lock associated with futex> (FUTEX_WORD);
+     lock (l);
+     for (res = 0; PROCESSES_TO_WAKE > 0; PROCESSES_TO_WAKE--, res++) {
+       if (<no process blocked on futex>) break;
+       wf = <get wait_flag of a process blocked on futex> (FUTEX_WORD);
+       // No happens-before guarantee with woken futex_wait (see above)
+       atomic_store_relaxed (wf, 0);
+     }
+     return res;
+
+   Note that we need to support futex_wake calls to past futexes whose memory
+   has potentially been reused due to POSIX' requirements on synchronization
+   object destruction (see above); therefore, we must not report or abort
+   on most errors.  */
+static __always_inline void
+futex_wake (unsigned int* futex_word, int processes_to_wake, int private);
+
+/* Calls __libc_fatal with an error message.  Convenience function for
+   concrete implementations of the futex interface.  */
+static __always_inline __attribute__ ((__noreturn__)) void
+futex_fatal_error (void)
+{
+  __libc_fatal ("The futex facility returned an unexpected error code.");
+}
+
+#endif  /* futex-internal.h */
diff --git a/sysdeps/nptl/gai_misc.h b/sysdeps/nptl/gai_misc.h
index a34dbc0..96c8fa0 100644
--- a/sysdeps/nptl/gai_misc.h
+++ b/sysdeps/nptl/gai_misc.h
@@ -23,14 +23,14 @@ 
 #include <assert.h>
 #include <signal.h>
 #include <nptl/pthreadP.h>
-#include <lowlevellock.h>
+#include <futex-internal.h>
 
 #define DONT_NEED_GAI_MISC_COND	1
 
 #define GAI_MISC_NOTIFY(waitlist) \
   do {									      \
     if (*waitlist->counterp > 0 && --*waitlist->counterp == 0)		      \
-      lll_futex_wake (waitlist->counterp, 1, LLL_PRIVATE);		      \
+      futex_wake ((unsigned int *) waitlist->counterp, 1, FUTEX_PRIVATE);     \
   } while (0)
 
 #define GAI_MISC_WAIT(result, futex, timeout, cancel) \
@@ -49,9 +49,9 @@ 
 	int status;							      \
 	do								      \
 	  {								      \
-	    status = lll_futex_timed_wait (futexaddr, oldval, timeout,	      \
-					   LLL_PRIVATE);		      \
-	    if (status != -EWOULDBLOCK)					      \
+	    status = futex_reltimed_wait ((unsigned int *) futexaddr, oldval, \
+					  timeout, FUTEX_PRIVATE);	      \
+	    if (status != EAGAIN)					      \
 	      break;							      \
 									      \
 	    oldval = *futexaddr;					      \
@@ -61,12 +61,12 @@ 
 	if (cancel)							      \
 	  LIBC_CANCEL_RESET (oldtype);					      \
 									      \
-	if (status == -EINTR)						      \
+	if (status == EINTR)						      \
 	  result = EINTR;						      \
-	else if (status == -ETIMEDOUT)					      \
+	else if (status == ETIMEDOUT)					      \
 	  result = EAGAIN;						      \
 	else								      \
-	  assert (status == 0 || status == -EWOULDBLOCK);		      \
+	  assert (status == 0 || status == EAGAIN);			      \
 									      \
 	pthread_mutex_lock (&__gai_requests_mutex);			      \
       }									      \
diff --git a/sysdeps/unix/sysv/linux/futex-internal.h b/sysdeps/unix/sysv/linux/futex-internal.h
new file mode 100644
index 0000000..aca0911
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/futex-internal.h
@@ -0,0 +1,251 @@ 
+/* futex operations for glibc-internal use.  Linux version.
+   Copyright (C) 2014-2015 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef FUTEX_INTERNAL_H
+#define FUTEX_INTERNAL_H
+
+#include <sysdeps/nptl/futex-internal.h>
+#include <errno.h>
+#include <lowlevellock-futex.h>
+#include <nptl/pthreadP.h>
+
+/* See sysdeps/nptl/futex-internal.h for documentation; this file only
+   contains Linux-specific comments.
+
+   The Linux kernel treats provides absolute timeouts based on the
+   CLOCK_REALTIME clock and relative timeouts measured against the
+   CLOCK_MONOTONIC clock.
+
+   We expect a Linux kernel version of 2.6.22 or more recent (since this
+   version, EINTR is not returned on spurious wake-ups anymore).  */
+
+/* FUTEX_SHARED is always supported by the Linux kernel.  */
+static __always_inline int
+futex_supports_pshared (int pshared)
+{
+  if (__glibc_likely (pshared == PTHREAD_PROCESS_PRIVATE))
+    return 0;
+  else if (pshared == PTHREAD_PROCESS_SHARED)
+    return 0;
+  else
+    return EINVAL;
+}
+
+/* The Linux kernel supports relative timeouts measured against the
+   CLOCK_MONOTONIC clock.  */
+static __always_inline bool
+futex_supports_exact_relative_timeouts (void)
+{
+  return true;
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_wait (unsigned int *futex_word, unsigned int expected, int private)
+{
+  int err = lll_futex_timed_wait (futex_word, expected, NULL, private);
+  switch (err)
+    {
+    case 0:
+    case -EAGAIN:
+    case -EINTR:
+      return -err;
+
+    case -ETIMEDOUT: /* Cannot have happened as we provided no timeout.  */
+    case -EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case -EINVAL: /* Either due to wrong alignment or due to the timeout not
+		     being normalized.  Must have been caused by a glibc or
+		     application bug.  */
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_wait_cancelable (unsigned int *futex_word, unsigned int expected,
+		       int private)
+{
+  int oldtype;
+  oldtype = __pthread_enable_asynccancel ();
+  int err = lll_futex_timed_wait (futex_word, expected, NULL, private);
+  __pthread_disable_asynccancel (oldtype);
+  switch (err)
+    {
+    case 0:
+    case -EAGAIN:
+    case -EINTR:
+      return -err;
+
+    case -ETIMEDOUT: /* Cannot have happened as we provided no timeout.  */
+    case -EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case -EINVAL: /* Either due to wrong alignment or due to the timeout not
+		     being normalized.  Must have been caused by a glibc or
+		     application bug.  */
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_reltimed_wait (unsigned int *futex_word, unsigned int expected,
+		     const struct timespec *reltime, int private)
+{
+  int err = lll_futex_timed_wait (futex_word, expected, reltime, private);
+  switch (err)
+    {
+    case 0:
+    case -EAGAIN:
+    case -EINTR:
+    case -ETIMEDOUT:
+      return -err;
+
+    case -EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case -EINVAL: /* Either due to wrong alignment or due to the timeout not
+		     being normalized.  Must have been caused by a glibc or
+		     application bug.  */
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_reltimed_wait_cancelable (unsigned int *futex_word,
+				unsigned int expected,
+			        const struct timespec *reltime, int private)
+{
+  int oldtype;
+  oldtype = __pthread_enable_asynccancel ();
+  int err = lll_futex_timed_wait (futex_word, expected, reltime, private);
+  __pthread_disable_asynccancel (oldtype);
+  switch (err)
+    {
+    case 0:
+    case -EAGAIN:
+    case -EINTR:
+    case -ETIMEDOUT:
+      return -err;
+
+    case -EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case -EINVAL: /* Either due to wrong alignment or due to the timeout not
+		     being normalized.  Must have been caused by a glibc or
+		     application bug.  */
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_abstimed_wait (unsigned int *futex_word, unsigned int expected,
+		     const struct timespec *abstime, int private)
+{
+  /* Work around the fact that the kernel rejects negative timeout values
+     despite them being valid.  */
+  if (__glibc_unlikely ((abstime != NULL) && (abstime->tv_sec < 0)))
+    return ETIMEDOUT;
+  int err = lll_futex_timed_wait_bitset (futex_word, expected, abstime,
+					 FUTEX_CLOCK_REALTIME, private);
+  switch (err)
+    {
+    case 0:
+    case -EAGAIN:
+    case -EINTR:
+    case -ETIMEDOUT:
+      return -err;
+
+    case -EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case -EINVAL: /* Either due to wrong alignment or due to the timeout not
+		     being normalized.  Must have been caused by a glibc or
+		     application bug.  */
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline int
+futex_abstimed_wait_cancelable (unsigned int *futex_word,
+				unsigned int expected,
+			        const struct timespec *abstime, int private)
+{
+  /* Work around the fact that the kernel rejects negative timeout values
+     despite them being valid.  */
+  if (__glibc_unlikely ((abstime != NULL) && (abstime->tv_sec < 0)))
+    return ETIMEDOUT;
+  int oldtype;
+  oldtype = __pthread_enable_asynccancel ();
+  int err = lll_futex_timed_wait_bitset (futex_word, expected, abstime,
+					 FUTEX_CLOCK_REALTIME, private);
+  __pthread_disable_asynccancel (oldtype);
+  switch (err)
+    {
+    case 0:
+    case -EAGAIN:
+    case -EINTR:
+    case -ETIMEDOUT:
+      return -err;
+
+    case -EFAULT: /* Must have been caused by a glibc or application bug.  */
+    case -EINVAL: /* Either due to wrong alignment or due to the timeout not
+		     being normalized.  Must have been caused by a glibc or
+		     application bug.  */
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+/* See sysdeps/nptl/futex-internal.h for details.  */
+static __always_inline void
+futex_wake (unsigned int *futex_word, int processes_to_wake, int private)
+{
+  int res = lll_futex_wake (futex_word, processes_to_wake, private);
+  /* No error.  Ignore the number of woken processes.  */
+  if (res >= 0)
+    return;
+  switch (res)
+    {
+    case -EFAULT: /* Could have happened due to memory reuse.  */
+    case -EINVAL: /* Could be either due to incorrect alignment (a bug in
+		     glibc or in the application) or due to memory being
+		     reused for a PI futex.  We cannot distinguish between the
+		     two causes, and one of them is correct use, so we do not
+		     act in this case.  */
+      return;
+    case -ENOSYS: /* Must have been caused by a glibc bug.  */
+    /* No other errors are documented at this time.  */
+    default:
+      futex_fatal_error ();
+    }
+}
+
+#endif  /* futex-internal.h */