Patchwork Caching of PID/TID after fork

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Submitter Adhemerval Zanella Netto
Date Oct. 10, 2016, 6:03 p.m.
Message ID <ecb5be63-de88-f05c-38ad-65e20f17a274@linaro.org>
Download mbox | patch
Permalink /patch/16413/
State New
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Comments

Adhemerval Zanella Netto - Oct. 10, 2016, 6:03 p.m.
On 09/10/2016 11:19, Robert Święcki wrote:
>>> Though, one useful feature which could be potentially useful for some
>>> porjects would be to create a detached process (for which the kernel
>>> doesn't send termination signal - usually SIGCHLD - to the parent
>>> process). And this cannot be solved by ORing custom flags with fork
>>> ones, because SIGCHLD is already there. But, it's just a guess.
>>
>> Yes, I know of some cases where this would have helped as well.
>>
>> If we go the fork-with-flags route, we should translate glibc-specific
>> flags to kernel flags anyway because the kernel might introduce new
>> flags which break the interface in subtle ways (see O_TMPFILE and mode
>> argument handling).
> 
> An initial stab at the interface; it should avoid the problem you've
> described above? I don't think additional rewrite of clone flags would
> be required with such interface, even with future changes in the
> kernel - in any case, using it requires good understanding of the
> underlying kernel's clone() interface.
> 
> /* fork with flags */
> pid_t ffork(int mode, unsigned long flags);
> 
> mode:
>  FFORK_FLAG_SET - set flags directly
>  FFORK_FLAG_OR - append flags to whatever fork uses internally
> 
> flags:
>  as with clone()
> 
> ret val / errno:
>  as with fork()
> 

I really do not think adding a another GLIBC/GNU specific extension to
circumvent a possible misused implementation detail should be way to
handle this specific issue.

For the pid/tid caching problem I see it is feasible to just get rid of
pid caching and adjust the implementation that rely on this.  The cached
pid is used basically in tgkill interface on both setxid, sigcancel
checking, pthread_{kill,cancel,sigqueue}, and getpid.  And for all
implementation it used basically as an optimization to avoid the syscall,
while 'fork' has a lot of internal control to avoid invalidate its
value.

We can just replace the cached value with a direct syscall with some
less performance (the getpid syscall), while both the {v}fork arch
defined implementation would be simpler (including getpid).  Also,
fork won't require any set/reset the cached value, which also only
adds complexity.

It also simplifies the nptl_db code as well, since no extra check would
require to validate the pid cached value between forks.

Now, about the stack argument checking, I also think it is now feasible
to remove since clone itself won't require to operate in any thread
implicit data.  What I am not sure if this semantic change would require
a compatibility symbol.

Below is a RFC patch to implement the first options (pid caching removal)
only for x86_64.  I think I covered all cases of caching PID field
(I basically renamed its field and covered all the build failures).  It
shows no regression on x86_64.

--
Florian Weimer - Nov. 4, 2016, 3:14 p.m.
On 10/10/2016 08:03 PM, Adhemerval Zanella wrote:
> +  /* Some sanity checks for clone syscall: returned ppid should be currernt

Typo: “currernt”

On its own, this approach looks okay, but I am worried that it sends a 
message that it's okay to clone processes without additional measures to 
protect PRNGs and things like that.

Florian
Adhemerval Zanella Netto - Nov. 4, 2016, 4:03 p.m.
On 04/11/2016 13:14, Florian Weimer wrote:
> On 10/10/2016 08:03 PM, Adhemerval Zanella wrote:
>> +  /* Some sanity checks for clone syscall: returned ppid should be currernt
> 
> Typo: “currernt”
> 
> On its own, this approach looks okay, but I am worried that it sends a message that it's okay to clone processes without additional measures to protect PRNGs and things like that.
> 
> Florian

I am not sure if you referring you to my initial RFC patch or the one 
complete I sent [1] since you replied to the original thread.

Anyway, I see that with current fixes on some algorithm (execv not
using dynamic memory allocation and various issues with posix_spawn)
clone direct usage should be really required in very specific
scanerios (mostly on new containers projects and such alike).  And 
I would expect that these very projects to know the constraints and 
limitations of using the syscall directly.

[1] https://sourceware.org/ml/libc-alpha/2016-10/msg00233.html
Florian Weimer - Nov. 7, 2016, 4:04 p.m.
On 11/04/2016 05:03 PM, Adhemerval Zanella wrote:
>
>
> On 04/11/2016 13:14, Florian Weimer wrote:
>> On 10/10/2016 08:03 PM, Adhemerval Zanella wrote:
>>> +  /* Some sanity checks for clone syscall: returned ppid should be currernt
>>
>> Typo: “currernt”
>>
>> On its own, this approach looks okay, but I am worried that it sends a message that it's okay to clone processes without additional measures to protect PRNGs and things like that.
>>
>> Florian
>
> I am not sure if you referring you to my initial RFC patch or the one
> complete I sent [1] since you replied to the original thread.

Oh, I'll have a look at the updated patch then.

Florian

Patch

diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index 3016a2e..98a0ea2 100644
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -438,9 +438,6 @@  allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
       SETUP_THREAD_SYSINFO (pd);
 #endif
 
-      /* The process ID is also the same as that of the caller.  */
-      pd->pid = THREAD_GETMEM (THREAD_SELF, pid);
-
       /* Don't allow setxid until cloned.  */
       pd->setxid_futex = -1;
 
@@ -577,9 +574,6 @@  allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
 	  /* Don't allow setxid until cloned.  */
 	  pd->setxid_futex = -1;
 
-	  /* The process ID is also the same as that of the caller.  */
-	  pd->pid = THREAD_GETMEM (THREAD_SELF, pid);
-
 	  /* Allocate the DTV for this thread.  */
 	  if (_dl_allocate_tls (TLS_TPADJ (pd)) == NULL)
 	    {
@@ -873,9 +867,6 @@  __reclaim_stacks (void)
 	  /* This marks the stack as free.  */
 	  curp->tid = 0;
 
-	  /* The PID field must be initialized for the new process.  */
-	  curp->pid = self->pid;
-
 	  /* Account for the size of the stack.  */
 	  stack_cache_actsize += curp->stackblock_size;
 
@@ -901,13 +892,6 @@  __reclaim_stacks (void)
 	}
     }
 
-  /* Reset the PIDs in any cached stacks.  */
-  list_for_each (runp, &stack_cache)
-    {
-      struct pthread *curp = list_entry (runp, struct pthread, list);
-      curp->pid = self->pid;
-    }
-
   /* Add the stack of all running threads to the cache.  */
   list_splice (&stack_used, &stack_cache);
 
@@ -1052,9 +1036,9 @@  setxid_signal_thread (struct xid_command *cmdp, struct pthread *t)
     return 0;
 
   int val;
+  pid_t pid = __getpid ();
   INTERNAL_SYSCALL_DECL (err);
-  val = INTERNAL_SYSCALL (tgkill, err, 3, THREAD_GETMEM (THREAD_SELF, pid),
-			  t->tid, SIGSETXID);
+  val = INTERNAL_SYSCALL_CALL (tgkill, err, pid, t->tid, SIGSETXID);
 
   /* If this failed, it must have had not started yet or else exited.  */
   if (!INTERNAL_SYSCALL_ERROR_P (val, err))
diff --git a/nptl/descr.h b/nptl/descr.h
index 8e4938d..17a2c9f 100644
--- a/nptl/descr.h
+++ b/nptl/descr.h
@@ -167,7 +167,7 @@  struct pthread
      therefore stack) used' flag.  */
   pid_t tid;
 
-  /* Process ID - thread group ID in kernel speak.  */
+  /* Ununsed.  */
   pid_t pid;
 
   /* List of robust mutexes the thread is holding.  */
diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c
index bdbdfed..48fab50 100644
--- a/nptl/nptl-init.c
+++ b/nptl/nptl-init.c
@@ -184,18 +184,12 @@  __nptl_set_robust (struct pthread *self)
 static void
 sigcancel_handler (int sig, siginfo_t *si, void *ctx)
 {
-  /* Determine the process ID.  It might be negative if the thread is
-     in the middle of a fork() call.  */
-  pid_t pid = THREAD_GETMEM (THREAD_SELF, pid);
-  if (__glibc_unlikely (pid < 0))
-    pid = -pid;
-
   /* Safety check.  It would be possible to call this function for
      other signals and send a signal from another process.  This is not
      correct and might even be a security problem.  Try to catch as
      many incorrect invocations as possible.  */
   if (sig != SIGCANCEL
-      || si->si_pid != pid
+      || si->si_pid != __getpid()
       || si->si_code != SI_TKILL)
     return;
 
@@ -243,19 +237,14 @@  struct xid_command *__xidcmd attribute_hidden;
 static void
 sighandler_setxid (int sig, siginfo_t *si, void *ctx)
 {
-  /* Determine the process ID.  It might be negative if the thread is
-     in the middle of a fork() call.  */
-  pid_t pid = THREAD_GETMEM (THREAD_SELF, pid);
   int result;
-  if (__glibc_unlikely (pid < 0))
-    pid = -pid;
 
   /* Safety check.  It would be possible to call this function for
      other signals and send a signal from another process.  This is not
      correct and might even be a security problem.  Try to catch as
      many incorrect invocations as possible.  */
   if (sig != SIGSETXID
-      || si->si_pid != pid
+      || si->si_pid != __getpid ()
       || si->si_code != SI_TKILL)
     return;
 
diff --git a/nptl/pthread_cancel.c b/nptl/pthread_cancel.c
index 1419baf..89d02e1 100644
--- a/nptl/pthread_cancel.c
+++ b/nptl/pthread_cancel.c
@@ -22,7 +22,7 @@ 
 #include "pthreadP.h"
 #include <atomic.h>
 #include <sysdep.h>
-
+#include <unistd.h>
 
 int
 pthread_cancel (pthread_t th)
@@ -66,19 +66,11 @@  pthread_cancel (pthread_t th)
 #ifdef SIGCANCEL
 	  /* The cancellation handler will take care of marking the
 	     thread as canceled.  */
-	  INTERNAL_SYSCALL_DECL (err);
-
-	  /* One comment: The PID field in the TCB can temporarily be
-	     changed (in fork).  But this must not affect this code
-	     here.  Since this function would have to be called while
-	     the thread is executing fork, it would have to happen in
-	     a signal handler.  But this is no allowed, pthread_cancel
-	     is not guaranteed to be async-safe.  */
-	  int val;
-	  val = INTERNAL_SYSCALL (tgkill, err, 3,
-				  THREAD_GETMEM (THREAD_SELF, pid), pd->tid,
-				  SIGCANCEL);
+	  pid_t pid = getpid ();
 
+	  INTERNAL_SYSCALL_DECL (err);
+	  int val = INTERNAL_SYSCALL_CALL (tgkill, err, pid, pd->tid,
+					   SIGCANCEL);
 	  if (INTERNAL_SYSCALL_ERROR_P (val, err))
 	    result = INTERNAL_SYSCALL_ERRNO (val, err);
 #else
diff --git a/nptl/pthread_getattr_np.c b/nptl/pthread_getattr_np.c
index fb906f0..32d7484 100644
--- a/nptl/pthread_getattr_np.c
+++ b/nptl/pthread_getattr_np.c
@@ -68,7 +68,6 @@  pthread_getattr_np (pthread_t thread_id, pthread_attr_t *attr)
     {
       /* No stack information available.  This must be for the initial
 	 thread.  Get the info in some magical way.  */
-      assert (abs (thread->pid) == thread->tid);
 
       /* Stack size limit.  */
       struct rlimit rl;
diff --git a/nptl_db/td_ta_thr_iter.c b/nptl_db/td_ta_thr_iter.c
index a990fed..9e50599 100644
--- a/nptl_db/td_ta_thr_iter.c
+++ b/nptl_db/td_ta_thr_iter.c
@@ -76,48 +76,28 @@  iterate_thread_list (td_thragent_t *ta, td_thr_iter_f *callback,
       if (ps_pdread (ta->ph, addr, copy, ta->ta_sizeof_pthread) != PS_OK)
 	return TD_ERR;
 
-      /* Verify that this thread's pid field matches the child PID.
-	 If its pid field is negative, it's about to do a fork or it
-	 is the sole thread in a fork child.  */
-      psaddr_t pid;
-      err = DB_GET_FIELD_LOCAL (pid, ta, copy, pthread, pid, 0);
-      if (err == TD_OK && (pid_t) (uintptr_t) pid < 0)
-	{
-	  if (-(pid_t) (uintptr_t) pid == match_pid)
-	    /* It is about to do a fork, but is really still the parent PID.  */
-	    pid = (psaddr_t) (uintptr_t) match_pid;
-	  else
-	    /* It must be a fork child, whose new PID is in the tid field.  */
-	    err = DB_GET_FIELD_LOCAL (pid, ta, copy, pthread, tid, 0);
-	}
+      err = DB_GET_FIELD_LOCAL (schedpolicy, ta, copy, pthread,
+				schedpolicy, 0);
       if (err != TD_OK)
 	break;
+      err = DB_GET_FIELD_LOCAL (schedprio, ta, copy, pthread,
+				schedparam_sched_priority, 0);
+      if (err != TD_OK)
+	break;
+
+      /* Now test whether this thread matches the specified conditions.  */
 
-      if ((pid_t) (uintptr_t) pid == match_pid)
+      /* Only if the priority level is as high or higher.  */
+      int descr_pri = ((uintptr_t) schedpolicy == SCHED_OTHER
+		       ? 0 : (uintptr_t) schedprio);
+      if (descr_pri >= ti_pri)
 	{
-	  err = DB_GET_FIELD_LOCAL (schedpolicy, ta, copy, pthread,
-				    schedpolicy, 0);
-	  if (err != TD_OK)
-	    break;
-	  err = DB_GET_FIELD_LOCAL (schedprio, ta, copy, pthread,
-				    schedparam_sched_priority, 0);
-	  if (err != TD_OK)
-	    break;
-
-	  /* Now test whether this thread matches the specified conditions.  */
-
-	  /* Only if the priority level is as high or higher.  */
-	  int descr_pri = ((uintptr_t) schedpolicy == SCHED_OTHER
-			   ? 0 : (uintptr_t) schedprio);
-	  if (descr_pri >= ti_pri)
-	    {
-	      /* Yep, it matches.  Call the callback function.  */
-	      td_thrhandle_t th;
-	      th.th_ta_p = (td_thragent_t *) ta;
-	      th.th_unique = addr;
-	      if (callback (&th, cbdata_p) != 0)
-		return TD_DBERR;
-	    }
+	  /* Yep, it matches.  Call the callback function.  */
+	  td_thrhandle_t th;
+	  th.th_ta_p = (td_thragent_t *) ta;
+	  th.th_unique = addr;
+	  if (callback (&th, cbdata_p) != 0)
+	    return TD_DBERR;
 	}
 
       /* Get the pointer to the next element.  */
diff --git a/nptl_db/td_thr_validate.c b/nptl_db/td_thr_validate.c
index f3c8a7b..9b89fec 100644
--- a/nptl_db/td_thr_validate.c
+++ b/nptl_db/td_thr_validate.c
@@ -80,28 +80,5 @@  td_thr_validate (const td_thrhandle_t *th)
 	err = TD_OK;
     }
 
-  if (err == TD_OK)
-    {
-      /* Verify that this is not a stale element in a fork child.  */
-      pid_t match_pid = ps_getpid (th->th_ta_p->ph);
-      psaddr_t pid;
-      err = DB_GET_FIELD (pid, th->th_ta_p, th->th_unique, pthread, pid, 0);
-      if (err == TD_OK && (pid_t) (uintptr_t) pid < 0)
-	{
-	  /* This was a thread that was about to fork, or it is the new sole
-	     thread in a fork child.  In the latter case, its tid was stored
-	     via CLONE_CHILD_SETTID and so is already the proper child PID.  */
-	  if (-(pid_t) (uintptr_t) pid == match_pid)
-	    /* It is about to do a fork, but is really still the parent PID.  */
-	    pid = (psaddr_t) (uintptr_t) match_pid;
-	  else
-	    /* It must be a fork child, whose new PID is in the tid field.  */
-	    err = DB_GET_FIELD (pid, th->th_ta_p, th->th_unique,
-				pthread, tid, 0);
-	}
-      if (err == TD_OK && (pid_t) (uintptr_t) pid != match_pid)
-	err = TD_NOTHR;
-    }
-
   return err;
 }
diff --git a/sysdeps/nptl/fork.c b/sysdeps/nptl/fork.c
index ea135f8..7294c08 100644
--- a/sysdeps/nptl/fork.c
+++ b/sysdeps/nptl/fork.c
@@ -132,15 +132,10 @@  __libc_fork (void)
     }
 
 #ifndef NDEBUG
-  pid_t ppid = THREAD_GETMEM (THREAD_SELF, tid);
+  INTERNAL_SYSCALL_DECL (err);
+  pid_t ppid = INTERNAL_SYSCALL_CALL (gettid, err);
 #endif
 
-  /* We need to prevent the getpid() code to update the PID field so
-     that, if a signal arrives in the child very early and the signal
-     handler uses getpid(), the value returned is correct.  */
-  pid_t parentpid = THREAD_GETMEM (THREAD_SELF, pid);
-  THREAD_SETMEM (THREAD_SELF, pid, -parentpid);
-
 #ifdef ARCH_FORK
   pid = ARCH_FORK ();
 #else
@@ -159,9 +154,6 @@  __libc_fork (void)
       if (__fork_generation_pointer != NULL)
 	*__fork_generation_pointer += __PTHREAD_ONCE_FORK_GEN_INCR;
 
-      /* Adjust the PID field for the new process.  */
-      THREAD_SETMEM (self, pid, THREAD_GETMEM (self, tid));
-
 #if HP_TIMING_AVAIL
       /* The CPU clock of the thread and process have to be set to zero.  */
       hp_timing_t now;
@@ -231,10 +223,7 @@  __libc_fork (void)
     }
   else
     {
-      assert (THREAD_GETMEM (THREAD_SELF, tid) == ppid);
-
-      /* Restore the PID value.  */
-      THREAD_SETMEM (THREAD_SELF, pid, parentpid);
+      assert (THREAD_GETMEM (THREAD_SELF, tid) == 0);
 
       /* Release acquired locks in the multi-threaded case.  */
       if (multiple_threads)
diff --git a/sysdeps/unix/sysv/linux/createthread.c b/sysdeps/unix/sysv/linux/createthread.c
index 6d32cec..ec86f50 100644
--- a/sysdeps/unix/sysv/linux/createthread.c
+++ b/sysdeps/unix/sysv/linux/createthread.c
@@ -128,10 +128,10 @@  create_thread (struct pthread *pd, const struct pthread_attr *attr,
 	      /* The operation failed.  We have to kill the thread.
 		 We let the normal cancellation mechanism do the work.  */
 
+	      pid_t pid = __getpid ();
 	      INTERNAL_SYSCALL_DECL (err2);
-	      (void) INTERNAL_SYSCALL (tgkill, err2, 3,
-				       THREAD_GETMEM (THREAD_SELF, pid),
-				       pd->tid, SIGCANCEL);
+	      (void) INTERNAL_SYSCALL_CALL (tgkill, err2, pid, pd->tid,
+					    SIGCANCEL);
 
 	      return INTERNAL_SYSCALL_ERRNO (res, err);
 	    }
diff --git a/sysdeps/unix/sysv/linux/getpid.c b/sysdeps/unix/sysv/linux/getpid.c
index 1124549..2bfafed 100644
--- a/sysdeps/unix/sysv/linux/getpid.c
+++ b/sysdeps/unix/sysv/linux/getpid.c
@@ -20,43 +20,11 @@ 
 #include <tls.h>
 #include <sysdep.h>
 
-
-#if IS_IN (libc)
-static inline __attribute__((always_inline)) pid_t really_getpid (pid_t oldval);
-
-static inline __attribute__((always_inline)) pid_t
-really_getpid (pid_t oldval)
-{
-  if (__glibc_likely (oldval == 0))
-    {
-      pid_t selftid = THREAD_GETMEM (THREAD_SELF, tid);
-      if (__glibc_likely (selftid != 0))
-	return selftid;
-    }
-
-  INTERNAL_SYSCALL_DECL (err);
-  pid_t result = INTERNAL_SYSCALL (getpid, err, 0);
-
-  /* We do not set the PID field in the TID here since we might be
-     called from a signal handler while the thread executes fork.  */
-  if (oldval == 0)
-    THREAD_SETMEM (THREAD_SELF, tid, result);
-  return result;
-}
-#endif
-
 pid_t
 __getpid (void)
 {
-#if !IS_IN (libc)
   INTERNAL_SYSCALL_DECL (err);
-  pid_t result = INTERNAL_SYSCALL (getpid, err, 0);
-#else
-  pid_t result = THREAD_GETMEM (THREAD_SELF, pid);
-  if (__glibc_unlikely (result <= 0))
-    result = really_getpid (result);
-#endif
-  return result;
+  return INTERNAL_SYSCALL_CALL (getpid, err);
 }
 
 libc_hidden_def (__getpid)
diff --git a/sysdeps/unix/sysv/linux/pthread-pids.h b/sysdeps/unix/sysv/linux/pthread-pids.h
index d42bba0..618a5b1 100644
--- a/sysdeps/unix/sysv/linux/pthread-pids.h
+++ b/sysdeps/unix/sysv/linux/pthread-pids.h
@@ -26,5 +26,5 @@  static inline void
 __pthread_initialize_pids (struct pthread *pd)
 {
   INTERNAL_SYSCALL_DECL (err);
-  pd->pid = pd->tid = INTERNAL_SYSCALL (set_tid_address, err, 1, &pd->tid);
+  pd->tid = INTERNAL_SYSCALL_CALL (set_tid_address, err, &pd->tid);
 }
diff --git a/sysdeps/unix/sysv/linux/pthread_kill.c b/sysdeps/unix/sysv/linux/pthread_kill.c
index bcb3009..15c9ba6 100644
--- a/sysdeps/unix/sysv/linux/pthread_kill.c
+++ b/sysdeps/unix/sysv/linux/pthread_kill.c
@@ -21,6 +21,7 @@ 
 #include <pthreadP.h>
 #include <tls.h>
 #include <sysdep.h>
+#include <unistd.h>
 
 
 int
@@ -49,14 +50,15 @@  __pthread_kill (pthread_t threadid, int signo)
   /* We have a special syscall to do the work.  */
   INTERNAL_SYSCALL_DECL (err);
 
+  pid_t pid = getpid ();
+
   /* One comment: The PID field in the TCB can temporarily be changed
      (in fork).  But this must not affect this code here.  Since this
      function would have to be called while the thread is executing
      fork, it would have to happen in a signal handler.  But this is
      no allowed, pthread_kill is not guaranteed to be async-safe.  */
   int val;
-  val = INTERNAL_SYSCALL (tgkill, err, 3, THREAD_GETMEM (THREAD_SELF, pid),
-			  tid, signo);
+  val = INTERNAL_SYSCALL_CALL (tgkill, err, pid, tid, signo);
 
   return (INTERNAL_SYSCALL_ERROR_P (val, err)
 	  ? INTERNAL_SYSCALL_ERRNO (val, err) : 0);
diff --git a/sysdeps/unix/sysv/linux/pthread_sigqueue.c b/sysdeps/unix/sysv/linux/pthread_sigqueue.c
index 7694d54..642366b 100644
--- a/sysdeps/unix/sysv/linux/pthread_sigqueue.c
+++ b/sysdeps/unix/sysv/linux/pthread_sigqueue.c
@@ -49,12 +49,14 @@  pthread_sigqueue (pthread_t threadid, int signo, const union sigval value)
   if (signo == SIGCANCEL || signo == SIGTIMER || signo == SIGSETXID)
     return EINVAL;
 
+  pid_t pid = getpid ();
+
   /* Set up the siginfo_t structure.  */
   siginfo_t info;
   memset (&info, '\0', sizeof (siginfo_t));
   info.si_signo = signo;
   info.si_code = SI_QUEUE;
-  info.si_pid = THREAD_GETMEM (THREAD_SELF, pid);
+  info.si_pid = pid;
   info.si_uid = getuid ();
   info.si_value = value;
 
@@ -66,9 +68,8 @@  pthread_sigqueue (pthread_t threadid, int signo, const union sigval value)
      function would have to be called while the thread is executing
      fork, it would have to happen in a signal handler.  But this is
      no allowed, pthread_sigqueue is not guaranteed to be async-safe.  */
-  int val = INTERNAL_SYSCALL (rt_tgsigqueueinfo, err, 4,
-			      THREAD_GETMEM (THREAD_SELF, pid),
-			      tid, signo, &info);
+  int val = INTERNAL_SYSCALL_CALL (rt_tgsigqueueinfo, err, pid, tid, signo,
+				   &info);
 
   return (INTERNAL_SYSCALL_ERROR_P (val, err)
 	  ? INTERNAL_SYSCALL_ERRNO (val, err) : 0);
diff --git a/sysdeps/unix/sysv/linux/tst-clone2.c b/sysdeps/unix/sysv/linux/tst-clone2.c
index 68a7e6d..2d6369e 100644
--- a/sysdeps/unix/sysv/linux/tst-clone2.c
+++ b/sysdeps/unix/sysv/linux/tst-clone2.c
@@ -28,8 +28,14 @@ 
 #include <stdlib.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <sys/syscall.h>
 
-#include <tls.h> /* for THREAD_* macros.  */
+#include <stackinfo.h>  /* For _STACK_GROWS_{UP,DOWN}.  */
+
+static int do_test (void);
+
+#define TEST_FUNCTION do_test ()
+#include <test-skeleton.c>
 
 static int sig;
 static int pipefd[2];
@@ -39,9 +45,12 @@  f (void *a)
 {
   close (pipefd[0]);
 
-  pid_t pid = THREAD_GETMEM (THREAD_SELF, pid);
-  pid_t tid = THREAD_GETMEM (THREAD_SELF, tid);
+  pid_t ppid = getppid ();
+  pid_t pid = getpid ();
+  pid_t tid = syscall (__NR_gettid);
 
+  while (write (pipefd[1], &ppid, sizeof ppid) < 0)
+    continue;
   while (write (pipefd[1], &pid, sizeof pid) < 0)
     continue;
   while (write (pipefd[1], &tid, sizeof tid) < 0)
@@ -52,26 +61,19 @@  f (void *a)
 
 
 static int
-clone_test (int clone_flags)
+do_test (void)
 {
   sig = SIGRTMIN;
   sigset_t ss;
   sigemptyset (&ss);
   sigaddset (&ss, sig);
   if (sigprocmask (SIG_BLOCK, &ss, NULL) != 0)
-    {
-      printf ("sigprocmask failed: %m\n");
-      return 1;
-    }
+    FAIL_EXIT1 ("sigprocmask failed: %m");
 
   if (pipe2 (pipefd, O_CLOEXEC))
-    {
-      printf ("sigprocmask failed: %m\n");
-      return 1;
-    }
-
-  pid_t ppid = getpid ();
+    FAIL_EXIT1 ("pipe failed: %m");
 
+  int clone_flags = 0;
 #ifdef __ia64__
   extern int __clone2 (int (*__fn) (void *__arg), void *__child_stack_base,
 		       size_t __child_stack_size, int __flags,
@@ -88,61 +90,47 @@  clone_test (int clone_flags)
 #error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
 #endif
 #endif
+
   close (pipefd[1]);
 
   if (p == -1)
+    FAIL_EXIT1("clone failed: %m");
+
+  pid_t ppid, pid, tid;
+  if (read (pipefd[0], &ppid, sizeof pid) != sizeof pid)
     {
-      printf ("clone failed: %m\n");
-      return 1;
+      kill (p, SIGKILL);
+      FAIL_EXIT1 ("read ppid failed: %m");
     }
-
-  pid_t pid, tid;
   if (read (pipefd[0], &pid, sizeof pid) != sizeof pid)
     {
-      printf ("read pid failed: %m\n");
       kill (p, SIGKILL);
-      return 1;
+      FAIL_EXIT1 ("read pid failed: %m");
     }
   if (read (pipefd[0], &tid, sizeof tid) != sizeof tid)
     {
-      printf ("read pid failed: %m\n");
       kill (p, SIGKILL);
-      return 1;
+      FAIL_EXIT1 ("read tid failed: %m");
     }
 
   close (pipefd[0]);
 
   int ret = 0;
 
-  /* For CLONE_VM glibc clone implementation does not change the pthread
-     pid/tid field.  */
-  if ((clone_flags & CLONE_VM) == CLONE_VM)
-    {
-      if ((ppid != pid) || (ppid != tid))
-	{
-	  printf ("parent pid (%i) != received pid/tid (%i/%i)\n",
-		  (int)ppid, (int)pid, (int)tid);
-	  ret = 1;
-	}
-    }
-  /* For any other flag clone updates the new pthread pid and tid with
-     the clone return value.  */
-  else
-    {
-      if ((p != pid) || (p != tid))
-	{
-	  printf ("child pid (%i) != received pid/tid (%i/%i)\n",
-		  (int)p, (int)pid, (int)tid);
-	  ret = 1;
-	}
-    }
+  pid_t own_pid = getpid ();
+  pid_t own_tid = syscall (__NR_gettid);
+
+  /* Some sanity checks for clone syscall: returned ppid should be currernt
+     pid and both returned tid/pid should be different from current one.  */
+  if ((ppid != own_pid) || (pid == own_pid) || (tid == own_tid))
+    FAIL_RET ("ppd=%i pid=%i tid=%i | own_pid=%i own_tid=%i",
+ 	      (int)ppid, (int)pid, (int)tid, (int)own_pid, (int)own_tid);
 
   int e;
   if (waitpid (p, &e, __WCLONE) != p)
     {
-      puts ("waitpid failed");
       kill (p, SIGKILL);
-      return 1;
+      FAIL_EXIT1 ("waitpid failed");
     }
   if (!WIFEXITED (e))
     {
@@ -150,29 +138,10 @@  clone_test (int clone_flags)
 	printf ("died from signal %s\n", strsignal (WTERMSIG (e)));
       else
 	puts ("did not terminate correctly");
-      return 1;
+      exit (EXIT_FAILURE);
     }
   if (WEXITSTATUS (e) != 0)
-    {
-      printf ("exit code %d\n", WEXITSTATUS (e));
-      return 1;
-    }
+    FAIL_EXIT1 ("exit code %d", WEXITSTATUS (e));
 
   return ret;
 }
-
-int
-do_test (void)
-{
-  /* First, check that the clone implementation, without any flag, updates
-     the struct pthread to contain the new PID and TID.  */
-  int ret = clone_test (0);
-  /* Second, check that with CLONE_VM the struct pthread PID and TID fields
-     remain unmodified after the clone.  Any modifications would cause problem
-     for the parent as described in bug 19957.  */
-  ret += clone_test (CLONE_VM);
-  return ret;
-}
-
-#define TEST_FUNCTION do_test ()
-#include "../test-skeleton.c"
diff --git a/sysdeps/unix/sysv/linux/x86_64/clone.S b/sysdeps/unix/sysv/linux/x86_64/clone.S
index 66f4b11..5629aed 100644
--- a/sysdeps/unix/sysv/linux/x86_64/clone.S
+++ b/sysdeps/unix/sysv/linux/x86_64/clone.S
@@ -91,14 +91,6 @@  L(thread_start):
 	   the outermost frame obviously.  */
 	xorl	%ebp, %ebp
 
-	andq	$CLONE_VM, %rdi
-	jne	1f
-	movl	$SYS_ify(getpid), %eax
-	syscall
-	movl	%eax, %fs:PID
-	movl	%eax, %fs:TID
-1:
-
 	/* Set up arguments for the function call.  */
 	popq	%rax		/* Function to call.  */
 	popq	%rdi		/* Argument.  */
diff --git a/sysdeps/unix/sysv/linux/x86_64/vfork.S b/sysdeps/unix/sysv/linux/x86_64/vfork.S
index 8332ade..cdd2dea 100644
--- a/sysdeps/unix/sysv/linux/x86_64/vfork.S
+++ b/sysdeps/unix/sysv/linux/x86_64/vfork.S
@@ -34,16 +34,6 @@  ENTRY (__vfork)
 	cfi_adjust_cfa_offset(-8)
 	cfi_register(%rip, %rdi)
 
-	/* Save the TCB-cached PID away in %esi, and then negate the TCB
-           field.  But if it's zero, set it to 0x80000000 instead.  See
-           raise.c for the logic that relies on this value.  */
-	movl	%fs:PID, %esi
-	movl	$0x80000000, %ecx
-	movl	%esi, %edx
-	negl	%edx
-	cmove	%ecx, %edx
-	movl	%edx, %fs:PID
-
 	/* Stuff the syscall number in RAX and enter into the kernel.  */
 	movl	$SYS_ify (vfork), %eax
 	syscall
@@ -52,14 +42,6 @@  ENTRY (__vfork)
 	pushq	%rdi
 	cfi_adjust_cfa_offset(8)
 
-	/* Restore the original value of the TCB cache of the PID, if we're
-	   the parent.  But in the child (syscall return value equals zero),
-	   leave things as they are.  */
-	testq	%rax, %rax
-	je	1f
-	movl	%esi, %fs:PID
-1:
-
 	cmpl	$-4095, %eax
 	jae SYSCALL_ERROR_LABEL		/* Branch forward if it failed.  */
 
diff --git a/sysdeps/x86_64/nptl/tcb-offsets.sym b/sysdeps/x86_64/nptl/tcb-offsets.sym
index aeb7526..8a25c48 100644
--- a/sysdeps/x86_64/nptl/tcb-offsets.sym
+++ b/sysdeps/x86_64/nptl/tcb-offsets.sym
@@ -4,7 +4,6 @@ 
 
 RESULT			offsetof (struct pthread, result)
 TID			offsetof (struct pthread, tid)
-PID			offsetof (struct pthread, pid)
 CANCELHANDLING		offsetof (struct pthread, cancelhandling)
 CLEANUP_JMP_BUF		offsetof (struct pthread, cleanup_jmp_buf)
 CLEANUP			offsetof (struct pthread, cleanup)