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65810f0ef0
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.
136 lines
4.0 KiB
C
136 lines
4.0 KiB
C
/* Copyright (C) 2003-2017 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Jakub Jelinek <jakub@redhat.com>, 2003.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#ifndef _LOWLEVELLOCK_H
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#define _LOWLEVELLOCK_H 1
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#include <time.h>
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#include <sys/param.h>
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#include <bits/pthreadtypes.h>
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#include <atomic.h>
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#include <kernel-features.h>
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#include <lowlevellock-futex.h>
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static inline int
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__attribute__ ((always_inline))
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__lll_trylock (int *futex)
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{
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return atomic_compare_and_exchange_val_24_acq (futex, 1, 0) != 0;
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}
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#define lll_trylock(futex) __lll_trylock (&(futex))
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static inline int
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__attribute__ ((always_inline))
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__lll_cond_trylock (int *futex)
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{
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return atomic_compare_and_exchange_val_24_acq (futex, 2, 0) != 0;
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}
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#define lll_cond_trylock(futex) __lll_cond_trylock (&(futex))
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extern void __lll_lock_wait_private (int *futex) attribute_hidden;
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extern void __lll_lock_wait (int *futex, int private) attribute_hidden;
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static inline void
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__attribute__ ((always_inline))
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__lll_lock (int *futex, int private)
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{
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int val = atomic_compare_and_exchange_val_24_acq (futex, 1, 0);
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if (__glibc_unlikely (val != 0))
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{
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if (__builtin_constant_p (private) && private == LLL_PRIVATE)
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__lll_lock_wait_private (futex);
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else
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__lll_lock_wait (futex, private);
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}
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}
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#define lll_lock(futex, private) __lll_lock (&(futex), private)
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static inline void
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__attribute__ ((always_inline))
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__lll_cond_lock (int *futex, int private)
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{
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int val = atomic_compare_and_exchange_val_24_acq (futex, 2, 0);
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if (__glibc_unlikely (val != 0))
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__lll_lock_wait (futex, private);
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}
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#define lll_cond_lock(futex, private) __lll_cond_lock (&(futex), private)
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extern int __lll_timedlock_wait (int *futex, const struct timespec *,
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int private) attribute_hidden;
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static inline int
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__attribute__ ((always_inline))
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__lll_timedlock (int *futex, const struct timespec *abstime, int private)
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{
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int val = atomic_compare_and_exchange_val_24_acq (futex, 1, 0);
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int result = 0;
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if (__glibc_unlikely (val != 0))
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result = __lll_timedlock_wait (futex, abstime, private);
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return result;
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}
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#define lll_timedlock(futex, abstime, private) \
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__lll_timedlock (&(futex), abstime, private)
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#define lll_unlock(lock, private) \
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((void) ({ \
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int *__futex = &(lock); \
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int __private = (private); \
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int __val = atomic_exchange_24_rel (__futex, 0); \
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if (__glibc_unlikely (__val > 1)) \
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lll_futex_wake (__futex, 1, __private); \
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}))
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#define lll_islocked(futex) \
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(futex != 0)
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/* Initializers for lock. */
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#define LLL_LOCK_INITIALIZER (0)
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#define LLL_LOCK_INITIALIZER_LOCKED (1)
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/* The kernel notifies a process which uses CLONE_CHILD_CLEARTID via futex
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wakeup when the clone terminates. The memory location contains the
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thread ID while the clone is running and is reset to zero
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afterwards. */
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#define lll_wait_tid(tid) \
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do \
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{ \
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__typeof (tid) __tid; \
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while ((__tid = (tid)) != 0) \
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lll_futex_wait (&(tid), __tid, LLL_SHARED); \
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} \
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while (0)
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extern int __lll_timedwait_tid (int *, const struct timespec *)
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attribute_hidden;
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#define lll_timedwait_tid(tid, abstime) \
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({ \
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int __res = 0; \
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if ((tid) != 0) \
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__res = __lll_timedwait_tid (&(tid), (abstime)); \
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__res; \
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})
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#endif /* lowlevellock.h */
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