robust mutexes: Fix broken x86 assembly by removing it

lll_robust_unlock on i386 and x86_64 first sets the futex word to
FUTEX_WAITERS|0 before calling __lll_unlock_wake, which will set the
futex word to 0.  If the thread is killed between these steps, then the
futex word will be FUTEX_WAITERS|0, and the kernel (at least current
upstream) will not set it to FUTEX_OWNER_DIED|FUTEX_WAITERS because 0 is
not equal to the TID of the crashed thread.

The lll_robust_lock assembly code on i386 and x86_64 is not prepared to
deal with this case because the fastpath tries to only CAS 0 to TID and
not FUTEX_WAITERS|0 to TID; the slowpath simply waits until it can CAS 0
to TID or the futex_word has the FUTEX_OWNER_DIED bit set.

This issue is fixed by removing the custom x86 assembly code and using
the generic C code instead.  However, instead of adding more duplicate
code to the custom x86 lowlevellock.h, the code of the lll_robust* functions
is inlined into the single call sites that exist for each of these functions
in the pthread_mutex_* functions.  The robust mutex paths in the latter
have been slightly reorganized to make them simpler.

This patch is meant to be easy to backport, so C11-style atomics are not
used.

	[BZ #20985]
	* nptl/Makefile: Adapt.
	* nptl/pthread_mutex_cond_lock.c (LLL_ROBUST_MUTEX_LOCK): Remove.
	(LLL_ROBUST_MUTEX_LOCK_MODIFIER): New.
	* nptl/pthread_mutex_lock.c (LLL_ROBUST_MUTEX_LOCK): Remove.
	(LLL_ROBUST_MUTEX_LOCK_MODIFIER): New.
	(__pthread_mutex_lock_full): Inline lll_robust* functions and adapt.
	* nptl/pthread_mutex_timedlock.c (pthread_mutex_timedlock): Inline
	lll_robust* functions and adapt.
	* nptl/pthread_mutex_unlock.c (__pthread_mutex_unlock_full): Likewise.
	* sysdeps/nptl/lowlevellock.h (__lll_robust_lock_wait,
	__lll_robust_lock, lll_robust_cond_lock, __lll_robust_timedlock_wait,
	__lll_robust_timedlock, __lll_robust_unlock): Remove.
	* sysdeps/unix/sysv/linux/i386/lowlevellock.h (lll_robust_lock,
	lll_robust_cond_lock, lll_robust_timedlock, lll_robust_unlock): Remove.
	* sysdeps/unix/sysv/linux/x86_64/lowlevellock.h (lll_robust_lock,
	lll_robust_cond_lock, lll_robust_timedlock, lll_robust_unlock): Remove.
	* sysdeps/unix/sysv/linux/sparc/lowlevellock.h (__lll_robust_lock_wait,
	__lll_robust_lock, lll_robust_cond_lock, __lll_robust_timedlock_wait,
	__lll_robust_timedlock, __lll_robust_unlock): Remove.
	* nptl/lowlevelrobustlock.c: Remove file.
	* nptl/lowlevelrobustlock.sym: Likewise.
	* sysdeps/unix/sysv/linux/i386/lowlevelrobustlock.S: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/lowlevelrobustlock.S: Likewise.

1 files changed, 0 insertions, 136 deletions

diff --git a/nptl/lowlevelrobustlock.c b/nptl/lowlevelrobustlock.c
deleted file mode 100644
index 3a91a6b9a7..0000000000
--- a/nptl/lowlevelrobustlock.c
+++ /dev/null
@@ -1,136 +0,0 @@
-/* Copyright (C) 2006-2017 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-   Contributed by Jakub Jelinek <jakub@redhat.com>, 2006.
-
-   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/>.  */
-
-#include <errno.h>
-#include <sysdep.h>
-#include <lowlevellock.h>
-#include <sys/time.h>
-#include <pthreadP.h>
-#include <kernel-features.h>
-
-
-int
-__lll_robust_lock_wait (int *futex, int private)
-{
-  int oldval = *futex;
-  int tid = THREAD_GETMEM (THREAD_SELF, tid);
-
-  /* If the futex changed meanwhile try locking again.  */
-  if (oldval == 0)
-    goto try;
-
-  do
-    {
-      /* If the owner died, return the present value of the futex.  */
-      if (__glibc_unlikely (oldval & FUTEX_OWNER_DIED))
-	return oldval;
-
-      /* Try to put the lock into state 'acquired, possibly with waiters'.  */
-      int newval = oldval | FUTEX_WAITERS;
-      if (oldval != newval
-	  && atomic_compare_and_exchange_bool_acq (futex, newval, oldval))
-	continue;
-
-      /* If *futex == 2, wait until woken.  */
-      lll_futex_wait (futex, newval, private);
-
-    try:
-      ;
-    }
-  while ((oldval = atomic_compare_and_exchange_val_acq (futex,
-							tid | FUTEX_WAITERS,
-							0)) != 0);
-  return 0;
-}
-
-
-int
-__lll_robust_timedlock_wait (int *futex, const struct timespec *abstime,
-			     int private)
-{
-  /* Reject invalid timeouts.  */
-  if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000)
-    return EINVAL;
-
-  int tid = THREAD_GETMEM (THREAD_SELF, tid);
-  int oldval = *futex;
-
-  /* If the futex changed meanwhile, try locking again.  */
-  if (oldval == 0)
-    goto try;
-
-  /* Work around the fact that the kernel rejects negative timeout values
-     despite them being valid.  */
-  if (__glibc_unlikely (abstime->tv_sec < 0))
-    return ETIMEDOUT;
-
-  do
-    {
-#if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
-     || !defined lll_futex_timed_wait_bitset)
-      struct timeval tv;
-      struct timespec rt;
-
-      /* Get the current time.  */
-      (void) __gettimeofday (&tv, NULL);
-
-      /* Compute relative timeout.  */
-      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;
-	}
-
-      /* Already timed out?  */
-      if (rt.tv_sec < 0)
-	return ETIMEDOUT;
-#endif
-
-      /* If the owner died, return the present value of the futex.  */
-      if (__glibc_unlikely (oldval & FUTEX_OWNER_DIED))
-	return oldval;
-
-      /* Try to put the lock into state 'acquired, possibly with waiters'.  */
-      int newval = oldval | FUTEX_WAITERS;
-      if (oldval != newval
-	  && atomic_compare_and_exchange_bool_acq (futex, newval, oldval))
-	continue;
-
-      /* If *futex == 2, wait until woken or timeout.  */
-#if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
-     || !defined lll_futex_timed_wait_bitset)
-      lll_futex_timed_wait (futex, newval, &rt, private);
-#else
-      int err = lll_futex_timed_wait_bitset (futex, newval, abstime,
-					     FUTEX_CLOCK_REALTIME, private);
-      /* The futex call timed out.  */
-      if (err == -ETIMEDOUT)
-         return -err;
-#endif
-
-    try:
-      ;
-    }
-  while ((oldval = atomic_compare_and_exchange_val_acq (futex,
-							tid | FUTEX_WAITERS,
-							0)) != 0);
-
-  return 0;
-}