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e8c659d74e
Add elision paths to the basic mutex locks. The normal path has a check for RTM and upgrades the lock to RTM when available. Trylocks cannot automatically upgrade, so they check for elision every time. We use a 4 byte value in the mutex to store the lock elision adaptation state. This is separate from the adaptive spin state and uses a separate field. Condition variables currently do not support elision. Recursive mutexes and condition variables may be supported at some point, but are not in the current implementation. Also "trylock" will not automatically enable elision unless some other lock call has been already called on the lock. This version does not use IFUNC, so it means every lock has one additional check for elision. Benchmarking showed the overhead to be negligible.
314 lines
8.9 KiB
C
314 lines
8.9 KiB
C
/* Copyright (C) 2002-2013 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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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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#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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#ifndef lll_unlock_elision
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#define lll_unlock_elision(a,b) ({ lll_unlock (a,b); 0; })
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#endif
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static int
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internal_function
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__pthread_mutex_unlock_full (pthread_mutex_t *mutex, int decr)
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__attribute_noinline__;
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int
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internal_function attribute_hidden
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__pthread_mutex_unlock_usercnt (mutex, decr)
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pthread_mutex_t *mutex;
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int decr;
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{
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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|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_unlock (mutex->__data.__lock, PTHREAD_MUTEX_PSHARED (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 (__builtin_expect (type == PTHREAD_MUTEX_TIMED_ELISION_NP, 1))
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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,
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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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static int
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internal_function
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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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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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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. */
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lll_robust_unlock (mutex->__data.__lock,
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PTHREAD_ROBUST_MUTEX_PSHARED (mutex));
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
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break;
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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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if ((mutex->__data.__kind & 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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if ((mutex->__data.__kind & 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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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. */
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if ((mutex->__data.__lock & FUTEX_WAITERS) != 0
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|| atomic_compare_and_exchange_bool_rel (&mutex->__data.__lock, 0,
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THREAD_GETMEM (THREAD_SELF,
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tid)))
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{
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int robust = mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP;
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int private = (robust
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? PTHREAD_ROBUST_MUTEX_PSHARED (mutex)
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: PTHREAD_MUTEX_PSHARED (mutex));
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INTERNAL_SYSCALL_DECL (__err);
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INTERNAL_SYSCALL (futex, __err, 2, &mutex->__data.__lock,
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__lll_private_flag (FUTEX_UNLOCK_PI, private));
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}
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
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break;
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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. */
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int newval, oldval;
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do
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{
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oldval = mutex->__data.__lock;
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newval = oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK;
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}
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while (atomic_compare_and_exchange_bool_rel (&mutex->__data.__lock,
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newval, oldval));
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if ((oldval & ~PTHREAD_MUTEX_PRIO_CEILING_MASK) > 1)
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lll_futex_wake (&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 (mutex)
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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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strong_alias (__pthread_mutex_unlock, pthread_mutex_unlock)
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hidden_def (__pthread_mutex_unlock)
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