30891f35fa
We stopped adding "Contributed by" or similar lines in sources in 2012 in favour of git logs and keeping the Contributors section of the glibc manual up to date. Removing these lines makes the license header a bit more consistent across files and also removes the possibility of error in attribution when license blocks or files are copied across since the contributed-by lines don't actually reflect reality in those cases. Move all "Contributed by" and similar lines (Written by, Test by, etc.) into a new file CONTRIBUTED-BY to retain record of these contributions. These contributors are also mentioned in manual/contrib.texi, so we just maintain this additional record as a courtesy to the earlier developers. The following scripts were used to filter a list of files to edit in place and to clean up the CONTRIBUTED-BY file respectively. These were not added to the glibc sources because they're not expected to be of any use in future given that this is a one time task: https://gist.github.com/siddhesh/b5ecac94eabfd72ed2916d6d8157e7dc https://gist.github.com/siddhesh/15ea1f5e435ace9774f485030695ee02 Reviewed-by: Carlos O'Donell <carlos@redhat.com>
381 lines
12 KiB
C
381 lines
12 KiB
C
/* Copyright (C) 2002-2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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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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<https://www.gnu.org/licenses/>. */
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#include <assert.h>
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#include <errno.h>
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#include <stdlib.h>
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#include "pthreadP.h"
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#include <lowlevellock.h>
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#include <stap-probe.h>
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#include <futex-internal.h>
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#include <shlib-compat.h>
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static int
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__pthread_mutex_unlock_full (pthread_mutex_t *mutex, int decr)
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__attribute_noinline__;
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/* lll_lock with single-thread optimization. */
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static inline void
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lll_mutex_unlock_optimized (pthread_mutex_t *mutex)
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{
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/* The single-threaded optimization is only valid for private
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mutexes. For process-shared mutexes, the mutex could be in a
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shared mapping, so synchronization with another process is needed
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even without any threads. */
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int private = PTHREAD_MUTEX_PSHARED (mutex);
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if (private == LLL_PRIVATE && SINGLE_THREAD_P)
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mutex->__data.__lock = 0;
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else
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lll_unlock (mutex->__data.__lock, private);
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}
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int
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__pthread_mutex_unlock_usercnt (pthread_mutex_t *mutex, int decr)
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{
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/* See concurrency notes regarding mutex type which is loaded from __kind
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in struct __pthread_mutex_s in sysdeps/nptl/bits/thread-shared-types.h. */
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int type = PTHREAD_MUTEX_TYPE_ELISION (mutex);
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if (__builtin_expect (type
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& ~(PTHREAD_MUTEX_KIND_MASK_NP
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|PTHREAD_MUTEX_ELISION_FLAGS_NP), 0))
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return __pthread_mutex_unlock_full (mutex, decr);
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if (__builtin_expect (type, PTHREAD_MUTEX_TIMED_NP)
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== PTHREAD_MUTEX_TIMED_NP)
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{
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/* Always reset the owner field. */
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normal:
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mutex->__data.__owner = 0;
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if (decr)
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/* One less user. */
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--mutex->__data.__nusers;
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/* Unlock. */
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lll_mutex_unlock_optimized (mutex);
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LIBC_PROBE (mutex_release, 1, mutex);
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return 0;
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}
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else if (__glibc_likely (type == PTHREAD_MUTEX_TIMED_ELISION_NP))
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{
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/* Don't reset the owner/users fields for elision. */
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return lll_unlock_elision (mutex->__data.__lock, mutex->__data.__elision,
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PTHREAD_MUTEX_PSHARED (mutex));
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}
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else if (__builtin_expect (PTHREAD_MUTEX_TYPE (mutex)
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== PTHREAD_MUTEX_RECURSIVE_NP, 1))
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{
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/* Recursive mutex. */
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if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid))
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return EPERM;
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if (--mutex->__data.__count != 0)
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/* We still hold the mutex. */
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return 0;
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goto normal;
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}
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else if (__builtin_expect (PTHREAD_MUTEX_TYPE (mutex)
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== PTHREAD_MUTEX_ADAPTIVE_NP, 1))
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goto normal;
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else
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{
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/* Error checking mutex. */
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assert (type == PTHREAD_MUTEX_ERRORCHECK_NP);
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if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid)
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|| ! lll_islocked (mutex->__data.__lock))
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return EPERM;
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goto normal;
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}
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}
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libc_hidden_def (__pthread_mutex_unlock_usercnt)
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static int
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__pthread_mutex_unlock_full (pthread_mutex_t *mutex, int decr)
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{
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int newowner = 0;
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int private;
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switch (PTHREAD_MUTEX_TYPE (mutex))
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{
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case PTHREAD_MUTEX_ROBUST_RECURSIVE_NP:
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/* Recursive mutex. */
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if ((mutex->__data.__lock & FUTEX_TID_MASK)
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== THREAD_GETMEM (THREAD_SELF, tid)
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&& __builtin_expect (mutex->__data.__owner
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== PTHREAD_MUTEX_INCONSISTENT, 0))
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{
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if (--mutex->__data.__count != 0)
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/* We still hold the mutex. */
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return ENOTRECOVERABLE;
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goto notrecoverable;
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}
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if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid))
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return EPERM;
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if (--mutex->__data.__count != 0)
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/* We still hold the mutex. */
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return 0;
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goto robust;
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case PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP:
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case PTHREAD_MUTEX_ROBUST_NORMAL_NP:
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case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP:
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if ((mutex->__data.__lock & FUTEX_TID_MASK)
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!= THREAD_GETMEM (THREAD_SELF, tid)
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|| ! lll_islocked (mutex->__data.__lock))
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return EPERM;
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/* If the previous owner died and the caller did not succeed in
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making the state consistent, mark the mutex as unrecoverable
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and make all waiters. */
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if (__builtin_expect (mutex->__data.__owner
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== PTHREAD_MUTEX_INCONSISTENT, 0))
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notrecoverable:
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newowner = PTHREAD_MUTEX_NOTRECOVERABLE;
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robust:
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/* Remove mutex from the list. */
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
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&mutex->__data.__list.__next);
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/* We must set op_pending before we dequeue the mutex. Also see
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comments at ENQUEUE_MUTEX. */
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__asm ("" ::: "memory");
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DEQUEUE_MUTEX (mutex);
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mutex->__data.__owner = newowner;
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if (decr)
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/* One less user. */
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--mutex->__data.__nusers;
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/* Unlock by setting the lock to 0 (not acquired); if the lock had
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FUTEX_WAITERS set previously, then wake any waiters.
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The unlock operation must be the last access to the mutex to not
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violate the mutex destruction requirements (see __lll_unlock). */
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private = PTHREAD_ROBUST_MUTEX_PSHARED (mutex);
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if (__glibc_unlikely ((atomic_exchange_rel (&mutex->__data.__lock, 0)
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& FUTEX_WAITERS) != 0))
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futex_wake ((unsigned int *) &mutex->__data.__lock, 1, private);
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/* We must clear op_pending after we release the mutex.
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FIXME However, this violates the mutex destruction requirements
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because another thread could acquire the mutex, destroy it, and
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reuse the memory for something else; then, if this thread crashes,
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and the memory happens to have a value equal to the TID, the kernel
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will believe it is still related to the mutex (which has been
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destroyed already) and will modify some other random object. */
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__asm ("" ::: "memory");
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
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break;
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/* The PI support requires the Linux futex system call. If that's not
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available, pthread_mutex_init should never have allowed the type to
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be set. So it will get the default case for an invalid type. */
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#ifdef __NR_futex
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case PTHREAD_MUTEX_PI_RECURSIVE_NP:
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/* Recursive mutex. */
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if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid))
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return EPERM;
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if (--mutex->__data.__count != 0)
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/* We still hold the mutex. */
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return 0;
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goto continue_pi_non_robust;
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case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP:
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/* Recursive mutex. */
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if ((mutex->__data.__lock & FUTEX_TID_MASK)
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== THREAD_GETMEM (THREAD_SELF, tid)
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&& __builtin_expect (mutex->__data.__owner
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== PTHREAD_MUTEX_INCONSISTENT, 0))
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{
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if (--mutex->__data.__count != 0)
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/* We still hold the mutex. */
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return ENOTRECOVERABLE;
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goto pi_notrecoverable;
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}
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if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid))
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return EPERM;
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if (--mutex->__data.__count != 0)
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/* We still hold the mutex. */
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return 0;
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goto continue_pi_robust;
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case PTHREAD_MUTEX_PI_ERRORCHECK_NP:
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case PTHREAD_MUTEX_PI_NORMAL_NP:
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case PTHREAD_MUTEX_PI_ADAPTIVE_NP:
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case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:
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case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
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case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP:
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if ((mutex->__data.__lock & FUTEX_TID_MASK)
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!= THREAD_GETMEM (THREAD_SELF, tid)
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|| ! lll_islocked (mutex->__data.__lock))
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return EPERM;
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/* If the previous owner died and the caller did not succeed in
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making the state consistent, mark the mutex as unrecoverable
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and make all waiters. */
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/* See concurrency notes regarding __kind in struct __pthread_mutex_s
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in sysdeps/nptl/bits/thread-shared-types.h. */
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if ((atomic_load_relaxed (&(mutex->__data.__kind))
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& PTHREAD_MUTEX_ROBUST_NORMAL_NP) != 0
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&& __builtin_expect (mutex->__data.__owner
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== PTHREAD_MUTEX_INCONSISTENT, 0))
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pi_notrecoverable:
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newowner = PTHREAD_MUTEX_NOTRECOVERABLE;
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/* See concurrency notes regarding __kind in struct __pthread_mutex_s
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in sysdeps/nptl/bits/thread-shared-types.h. */
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if ((atomic_load_relaxed (&(mutex->__data.__kind))
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& PTHREAD_MUTEX_ROBUST_NORMAL_NP) != 0)
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{
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continue_pi_robust:
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/* Remove mutex from the list.
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Note: robust PI futexes are signaled by setting bit 0. */
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
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(void *) (((uintptr_t) &mutex->__data.__list.__next)
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| 1));
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/* We must set op_pending before we dequeue the mutex. Also see
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comments at ENQUEUE_MUTEX. */
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__asm ("" ::: "memory");
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DEQUEUE_MUTEX (mutex);
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}
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continue_pi_non_robust:
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mutex->__data.__owner = newowner;
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if (decr)
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/* One less user. */
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--mutex->__data.__nusers;
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/* Unlock. Load all necessary mutex data before releasing the mutex
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to not violate the mutex destruction requirements (see
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lll_unlock). */
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/* See concurrency notes regarding __kind in struct __pthread_mutex_s
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in sysdeps/nptl/bits/thread-shared-types.h. */
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int robust = atomic_load_relaxed (&(mutex->__data.__kind))
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& PTHREAD_MUTEX_ROBUST_NORMAL_NP;
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private = (robust
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? PTHREAD_ROBUST_MUTEX_PSHARED (mutex)
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: PTHREAD_MUTEX_PSHARED (mutex));
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/* Unlock the mutex using a CAS unless there are futex waiters or our
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TID is not the value of __lock anymore, in which case we let the
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kernel take care of the situation. Use release MO in the CAS to
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synchronize with acquire MO in lock acquisitions. */
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int l = atomic_load_relaxed (&mutex->__data.__lock);
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do
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{
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if (((l & FUTEX_WAITERS) != 0)
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|| (l != THREAD_GETMEM (THREAD_SELF, tid)))
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{
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futex_unlock_pi ((unsigned int *) &mutex->__data.__lock,
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private);
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break;
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}
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}
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while (!atomic_compare_exchange_weak_release (&mutex->__data.__lock,
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&l, 0));
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/* This happens after the kernel releases the mutex but violates the
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mutex destruction requirements; see comments in the code handling
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PTHREAD_MUTEX_ROBUST_NORMAL_NP. */
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
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break;
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#endif /* __NR_futex. */
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case PTHREAD_MUTEX_PP_RECURSIVE_NP:
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/* Recursive mutex. */
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if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid))
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return EPERM;
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if (--mutex->__data.__count != 0)
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/* We still hold the mutex. */
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return 0;
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goto pp;
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case PTHREAD_MUTEX_PP_ERRORCHECK_NP:
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/* Error checking mutex. */
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if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid)
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|| (mutex->__data.__lock & ~ PTHREAD_MUTEX_PRIO_CEILING_MASK) == 0)
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return EPERM;
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/* FALLTHROUGH */
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case PTHREAD_MUTEX_PP_NORMAL_NP:
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case PTHREAD_MUTEX_PP_ADAPTIVE_NP:
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/* Always reset the owner field. */
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pp:
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mutex->__data.__owner = 0;
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if (decr)
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/* One less user. */
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--mutex->__data.__nusers;
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/* Unlock. Use release MO in the CAS to synchronize with acquire MO in
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lock acquisitions. */
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int newval;
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int oldval = atomic_load_relaxed (&mutex->__data.__lock);
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do
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{
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newval = oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK;
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}
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while (!atomic_compare_exchange_weak_release (&mutex->__data.__lock,
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&oldval, newval));
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if ((oldval & ~PTHREAD_MUTEX_PRIO_CEILING_MASK) > 1)
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futex_wake ((unsigned int *)&mutex->__data.__lock, 1,
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PTHREAD_MUTEX_PSHARED (mutex));
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int oldprio = newval >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
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LIBC_PROBE (mutex_release, 1, mutex);
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return __pthread_tpp_change_priority (oldprio, -1);
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default:
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/* Correct code cannot set any other type. */
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return EINVAL;
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}
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LIBC_PROBE (mutex_release, 1, mutex);
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return 0;
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}
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int
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___pthread_mutex_unlock (pthread_mutex_t *mutex)
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{
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return __pthread_mutex_unlock_usercnt (mutex, 1);
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}
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libc_hidden_ver (___pthread_mutex_unlock, __pthread_mutex_unlock)
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#ifndef SHARED
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strong_alias (___pthread_mutex_unlock, __pthread_mutex_unlock)
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#endif
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versioned_symbol (libpthread, ___pthread_mutex_unlock, pthread_mutex_unlock,
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GLIBC_2_0);
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#if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_34)
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compat_symbol (libpthread, ___pthread_mutex_unlock, __pthread_mutex_unlock,
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GLIBC_2_0);
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#endif
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