diff mbox

[v3] Add and use new glibc-internal futex API.

Message ID 1434987160.25759.26.camel@localhost.localdomain
State Dropped
Headers show

Commit Message

Torvald Riegel June 22, 2015, 3:32 p.m. UTC
This is a revision of
https://sourceware.org/ml/libc-alpha/2015-06/msg00596.html

Compared to v2, I've moved the absolute-timeout futex wait functionality
directly into futex-internal (ie, no new function in
lowlevellock-futex.h), and added checks for support for shared futexes
in several places.

This patch doesn't try to change how shared/private is represented in
the attributes for barrier, rwlock, mutex, and condvar.  I think it is
sufficient, and easier, to address this in follow-up patches, if we need
to.

Tested on x86_64-linux.


2015-06-22  Torvald Riegel  <triegel@redhat.com>

	* sysdeps/nptl/futex-internal.h: New file.
	* sysdeps/nacl/futex-internal.h: New file.
	* sysdeps/unix/sysv/linux/futex-internal.h: New file.
	* nptl/allocatestack.c (setxid_mark_thread): Use futex wrappers with
	error checking.
	(setxid_unmark_thread): Likewise.
	(__nptl_setxid): Likewise.
	(__wait_lookup_done): Likewise.
	* nptl/cancellation.c (__pthread_disable_asynccancel): Likewise.
	* nptl/nptl-init.c (sighandler_setxid): Likewise.
	* nptl/pthread_create.c (START_THREAD_DEFN): Likewise.
	* nptl/pthread_once.c (clear_once_control): Likewise.
	(__pthread_once_slow): Likewise.
	* nptl/unregister-atfork.c (__unregister_atfork): Likewise.
	* sysdeps/nacl/exit-thread.h (__exit_thread): Likewise.
	* sysdeps/nptl/aio_misc.h (AIO_MISC_NOTIFY, AIO_MISC_WAIT): Likewise.
	* sysdeps/nptl/fork.c (__libc_fork): Likewise.
	* sysdeps/nptl/gai_misc.h (GAI_MISC_NOTIFY, GAI_MISC_WAIT): Likewise.
	* nptl/pthread_rwlock_rdlock.c (__pthread_rwlock_rdlock_slow):
	Likewise.
	(__pthread_rwlock_rdlock): Likewise.
	* nptl/pthread_rwlock_timedrdlock.c (pthread_rwlock_timedrdlock):
	Likewise.
	* nptl/pthread_rwlock_timedwrlock.c (pthread_rwlock_timedwrlock):
	Likewise.
	* nptl/pthread_rwlock_tryrdlock.c (__pthread_rwlock_tryrdlock):
	Likewise.
	* nptl/pthread_rwlock_unlock.c (__pthread_rwlock_unlock): Likewise.
	* nptl/pthread_rwlock_wrlock.c (__pthread_rwlock_wrlock_slow:
	Likewise.
	* nptl/pthread_rwlock_init (__pthread_rwlock_init): Remove
	__ASSUME_PRIVATE_FUTEX check.
	* nptl/pthread_rwlockattr_setpshared (pthread_rwlockattr_setpshared):
	Check that shared futexes are supported.
	* nptl/pthread_barrier_wait.c (pthread_barrier_wait): Use futex
	wrappers with error checking.
	* nptl/pthread_barrier_init.c (pthread_barrier_init): Add comments,
	remove attribute sanity check and __ASSUME_PRIVATE_FUTEX check.
	* nptl/pthread_barrierattr_setpshared.c
	(pthread_barrierattr_setpshared): Check that shared futexes are
	supported.
	* nptl/pthread_condattr_setpshared.c (pthread_condattr_setpshared):
	Likewise.
	* nptl/pthread_mutexattr_setpshared.c (pthread_mutexattr_setpshared):
	Likewise.
	* nptl/sem_init.c (futex_private_if_supported): Remove.
	(__new_sem_init): Adapt and check that shared futexes are supported.
	* nptl/sem_open.c (sem_open): Likewise.
	* nptl/sem_post.c (futex_wake): Remove.
	* nptl/sem_waitcommon.c (futex_abstimed_wait, futex_wake): Remove.
	(do_futex_wait): Use futex wrappers with error checking.
	* nptl/sem_wait.c: Include lowlevellock.h.

Comments

Roland McGrath June 24, 2015, 11:22 p.m. UTC | #1
> @@ -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.

> --- 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.

> +  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);


> --- a/nptl/pthread_create.c
> +++ b/nptl/pthread_create.c
> @@ -414,7 +415,7 @@ 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 (&this->__lock, 1, /* XYZ */ FUTEX_SHARED);

Needs a cast.  Again, the field should probably change.  But as this one is
a type defined in a public header, we should probably just do casts and let
things lie for now.

> @@ -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.

> @@ -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);

Space after cast.

> --- 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 (&pd->tid, 1, FUTEX_PRIVATE);

Needs cast.

> --- /dev/null
> +++ b/sysdeps/nacl/futex-internal.h
> @@ -0,0 +1,257 @@
[...]
> +/* FUTEX_SHARED is not yet supported.  */
> +static __always_inline int
> +futex_supports_pshared (int pshared)
> +{
> +  if (pshared == PTHREADS_PROCESS_SHARED)
> +    return ENOTSUP;

Typo: s/PTHREADS_PROCESS_SHARED/PTHREAD_PROCESS_SHARED/

> +    /* 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.)

> +/* 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.

> +/* 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)

The * should be next to the variable name, not next to the type.
There are other instances of this in the file too.

> +  int err = __nacl_irt_futex.futex_wait_abs ((volatile int *) futex_word,
> +      expected, abstime);

The second line of arguments should be indented to just past the open paren.
There are other instances of this in the file too.

>  #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.

> +/* 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.

> +#include <errno.h>
> +#include <lowlevellock-futex.h>
> +#include <sys/time.h>
> +#include <stdlib.h>
> +#include <stdbool.h>
> +#include <nptl/pthreadP.h>

The only #include's the stub header should have are the ones necessary for
the API it defines.  I think that's just <stdbool.h> (for bool) and
<sys/time.h> (for struct timespec).

> +/* This file defines futex operations used internally in glibc.  A futex
> +   consists of the so-called futex word in userspace, which is of type int

But in this API it's of type 'unsigned int'.

> +/* 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

Encode these requirements in the code:

#if FUTEX_PRIVATE != 0
# error blah blah
#endif

> +/* 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).

> +/* Like futex_wait but cancelable.  */
> +static __always_inline int
> +futex_wait_cancelable (unsigned int *futex_word, unsigned int expected,
> +		       int private);

If "cancelable" means "is a cancellation point" in POSIX terminology,
then just write that.

> +/* 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 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.
> +   Returns ETIMEDOUT if the timeout expired.

Perhaps it would be better just to say the return values are all the same
ones as for futex_wait, plus the ETIMEDOUT case.  The same text repeated
in several comments is always likely to bit-rot later.

sysdeps/unix/sysv/linux/futex-internal.h has several of the trivial style
issues I cited above for the other variants.  I won't call them out in
detail.

> --- a/sysdeps/unix/sysv/linux/lowlevellock-futex.h
> +++ b/sysdeps/unix/sysv/linux/lowlevellock-futex.h
> @@ -22,6 +22,7 @@
>  #ifndef __ASSEMBLER__
>  #include <sysdep.h>
>  #include <tls.h>
> +#include <sys/time.h>
>  #include <kernel-features.h>
>  #endif

I don't see the need for this.


I will look into changing some internal fields from int to unsigned int
so as to reduce the number of casts required in calls to futex-internal.h
functions.


Thanks,
Roland
diff mbox

Patch

commit 240f215bff79cce28246920dafce8e21d5a97aab
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..7595186 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 +988,8 @@  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);
 
   /* Don't let the thread exit before the setxid handler runs.  */
@@ -1005,7 +1007,7 @@  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 ((unsigned int *) &t->setxid_futex, 1, FUTEX_PRIVATE);
 	    }
 	  return;
 	}
@@ -1032,7 +1034,7 @@  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 ((unsigned int *) &t->setxid_futex, 1, FUTEX_PRIVATE);
 }
 
 
@@ -1141,7 +1143,8 @@  __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 +1254,8 @@  __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 +1277,8 @@  __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..ea1bbc9 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 +94,7 @@  __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);
       newval = THREAD_GETMEM (self, cancelhandling);
     }
 }
diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c
index 8a51161..c875d3d 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 ((unsigned int *) &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..8190e78 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..9c71e11 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
@@ -31,6 +32,10 @@  pthread_barrierattr_setpshared (attr, pshared)
       && __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;
 
   iattr->pshared = pshared;
diff --git a/nptl/pthread_condattr_setpshared.c b/nptl/pthread_condattr_setpshared.c
index 3a760cf..7d352e9 100644
--- a/nptl/pthread_condattr_setpshared.c
+++ b/nptl/pthread_condattr_setpshared.c
@@ -18,6 +18,7 @@ 
 
 #include <errno.h>
 #include <pthreadP.h>
+#include <futex-internal.h>
 
 int
 pthread_condattr_setpshared (attr, pshared)
@@ -28,6 +29,10 @@  pthread_condattr_setpshared (attr, pshared)
       && __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;
 
   *valuep = (*valuep & ~1) | (pshared != PTHREAD_PROCESS_PRIVATE);
diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
index 71a5619..b23deb2 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 ((unsigned int *) &pd->setxid_futex, 1, FUTEX_PRIVATE);
 
 #ifdef __NR_set_robust_list
 # ifndef __ASSUME_SET_ROBUST_LIST
@@ -414,7 +415,7 @@  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 (&this->__lock, 1, /* XYZ */ FUTEX_SHARED);
 	}
       while (robust != (void *) &pd->robust_head);
     }
@@ -442,7 +443,12 @@  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 ((unsigned int *) &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 ((unsigned int *) &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..ee014b7 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
@@ -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;
+
   iattr = (struct pthread_mutexattr *) attr;
 
   if (pshared == PTHREAD_PROCESS_PRIVATE)
diff --git a/nptl/pthread_once.c b/nptl/pthread_once.c
index fe6d923..642730b 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..aa1593d 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..207918e 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..2f30022 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..ee0ab1f 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..b41c6ba 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..9c495d8 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..bff1dfe 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
@@ -31,6 +32,10 @@  pthread_rwlockattr_setpshared (attr, pshared)
       && __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;
 
   iattr->pshared = pshared;
diff --git a/nptl/sem_init.c b/nptl/sem_init.c
index 575b661..1ba5990 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..a092462 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 (&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..52b5583
--- /dev/null
+++ b/sysdeps/nacl/futex-internal.h
@@ -0,0 +1,257 @@ 
+/* 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 <errno.h>
+#include <lowlevellock-futex.h>
+#include <nacl-interfaces.h>
+#include <sys/time.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <nptl/pthreadP.h>
+#include <libc-internal.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 these
+   constants.  */
+#define FUTEX_PRIVATE LLL_PRIVATE
+/* Shared futexes are not yet supported, and we never allow clients to
+   actually request shared futexes.  Therefore, we do not need a different
+   value.  */
+#define FUTEX_SHARED  FUTEX_PRIVATE
+
+/* FUTEX_SHARED is not yet supported.  */
+static __always_inline int
+futex_supports_pshared (int pshared)
+{
+  if (pshared == PTHREADS_PROCESS_SHARED)
+    return ENOTSUP;
+  else
+    return 0;
+}
+
+/* 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:
+      abort ();
+    }
+}
+
+/* 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));
+}
+
+/* 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:
+      abort ();
+    }
+}
+
+/* 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:
+      abort ();
+    }
+}
+
+/* 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:
+      abort ();
+    }
+}
+
+/* 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:
+      abort ();
+    }
+}
+
+/* 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:
+      abort ();
+    }
+}
+
+/* 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:
+      abort ();
+    }
+}
+
+#endif  /* futex-internal.h */
diff --git a/sysdeps/nptl/aio_misc.h b/sysdeps/nptl/aio_misc.h
index fb69b0f..b648ac4 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..36f6675
--- /dev/null
+++ b/sysdeps/nptl/futex-internal.h
@@ -0,0 +1,194 @@ 
+/* futex operations for glibc-internal use.  Stub 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 <errno.h>
+#include <lowlevellock-futex.h>
+#include <sys/time.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <nptl/pthreadP.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 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_shared 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
+
+/* 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);
+
+/* 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);
+
+/* Like futex_wait but cancelable.  */
+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 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.
+   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 cancelable.  */
+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 cancelable.  */
+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);
+
+#endif  /* futex-internal.h */
diff --git a/sysdeps/nptl/gai_misc.h b/sysdeps/nptl/gai_misc.h
index bb83dca..f2dc327 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..660667e
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/futex-internal.h
@@ -0,0 +1,262 @@ 
+/* 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 <errno.h>
+#include <lowlevellock-futex.h>
+#include <sys/time.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <nptl/pthreadP.h>
+#include <libc-internal.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).  */
+
+/* See sysdeps/nptl/futex-internal.h for constraints on the value of these
+   constants.  */
+#define FUTEX_PRIVATE LLL_PRIVATE
+#define FUTEX_SHARED  LLL_SHARED
+
+/* FUTEX_SHARED is always supported by the Linux kernel.  */
+static __always_inline int
+futex_supports_pshared (int pshared)
+{
+  return 0;
+}
+
+/* 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:
+      abort ();
+    }
+}
+
+/* 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));
+}
+
+/* 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:
+      abort ();
+    }
+}
+
+/* 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:
+      abort ();
+    }
+}
+
+/* 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:
+      abort ();
+    }
+}
+
+/* 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:
+      abort ();
+    }
+}
+
+/* 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:
+      abort ();
+    }
+}
+
+/* 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:
+      abort ();
+    }
+}
+
+#endif  /* futex-internal.h */
diff --git a/sysdeps/unix/sysv/linux/lowlevellock-futex.h b/sysdeps/unix/sysv/linux/lowlevellock-futex.h
index 59f6627..cc9aae8 100644
--- a/sysdeps/unix/sysv/linux/lowlevellock-futex.h
+++ b/sysdeps/unix/sysv/linux/lowlevellock-futex.h
@@ -22,6 +22,7 @@ 
 #ifndef __ASSEMBLER__
 #include <sysdep.h>
 #include <tls.h>
+#include <sys/time.h>
 #include <kernel-features.h>
 #endif