glibc/nptl/pthread_mutex_unlock.c

381 lines
12 KiB
C

/* Copyright (C) 2002-2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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
<https://www.gnu.org/licenses/>. */
#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include "pthreadP.h"
#include <lowlevellock.h>
#include <stap-probe.h>
#include <futex-internal.h>
#include <shlib-compat.h>
static int
__pthread_mutex_unlock_full (pthread_mutex_t *mutex, int decr)
__attribute_noinline__;
/* lll_lock with single-thread optimization. */
static inline void
lll_mutex_unlock_optimized (pthread_mutex_t *mutex)
{
/* The single-threaded optimization is only valid for private
mutexes. For process-shared mutexes, the mutex could be in a
shared mapping, so synchronization with another process is needed
even without any threads. */
int private = PTHREAD_MUTEX_PSHARED (mutex);
if (private == LLL_PRIVATE && SINGLE_THREAD_P)
mutex->__data.__lock = 0;
else
lll_unlock (mutex->__data.__lock, private);
}
int
__pthread_mutex_unlock_usercnt (pthread_mutex_t *mutex, int decr)
{
/* See concurrency notes regarding mutex type which is loaded from __kind
in struct __pthread_mutex_s in sysdeps/nptl/bits/thread-shared-types.h. */
int type = PTHREAD_MUTEX_TYPE_ELISION (mutex);
if (__builtin_expect (type
& ~(PTHREAD_MUTEX_KIND_MASK_NP
|PTHREAD_MUTEX_ELISION_FLAGS_NP), 0))
return __pthread_mutex_unlock_full (mutex, decr);
if (__builtin_expect (type, PTHREAD_MUTEX_TIMED_NP)
== PTHREAD_MUTEX_TIMED_NP)
{
/* Always reset the owner field. */
normal:
mutex->__data.__owner = 0;
if (decr)
/* One less user. */
--mutex->__data.__nusers;
/* Unlock. */
lll_mutex_unlock_optimized (mutex);
LIBC_PROBE (mutex_release, 1, mutex);
return 0;
}
else if (__glibc_likely (type == PTHREAD_MUTEX_TIMED_ELISION_NP))
{
/* Don't reset the owner/users fields for elision. */
return lll_unlock_elision (mutex->__data.__lock, mutex->__data.__elision,
PTHREAD_MUTEX_PSHARED (mutex));
}
else if (__builtin_expect (PTHREAD_MUTEX_TYPE (mutex)
== PTHREAD_MUTEX_RECURSIVE_NP, 1))
{
/* Recursive mutex. */
if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid))
return EPERM;
if (--mutex->__data.__count != 0)
/* We still hold the mutex. */
return 0;
goto normal;
}
else if (__builtin_expect (PTHREAD_MUTEX_TYPE (mutex)
== PTHREAD_MUTEX_ADAPTIVE_NP, 1))
goto normal;
else
{
/* Error checking mutex. */
assert (type == PTHREAD_MUTEX_ERRORCHECK_NP);
if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid)
|| ! lll_islocked (mutex->__data.__lock))
return EPERM;
goto normal;
}
}
libc_hidden_def (__pthread_mutex_unlock_usercnt)
static int
__pthread_mutex_unlock_full (pthread_mutex_t *mutex, int decr)
{
int newowner = 0;
int private;
switch (PTHREAD_MUTEX_TYPE (mutex))
{
case PTHREAD_MUTEX_ROBUST_RECURSIVE_NP:
/* Recursive mutex. */
if ((mutex->__data.__lock & FUTEX_TID_MASK)
== THREAD_GETMEM (THREAD_SELF, tid)
&& __builtin_expect (mutex->__data.__owner
== PTHREAD_MUTEX_INCONSISTENT, 0))
{
if (--mutex->__data.__count != 0)
/* We still hold the mutex. */
return ENOTRECOVERABLE;
goto notrecoverable;
}
if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid))
return EPERM;
if (--mutex->__data.__count != 0)
/* We still hold the mutex. */
return 0;
goto robust;
case PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP:
case PTHREAD_MUTEX_ROBUST_NORMAL_NP:
case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP:
if ((mutex->__data.__lock & FUTEX_TID_MASK)
!= THREAD_GETMEM (THREAD_SELF, tid)
|| ! lll_islocked (mutex->__data.__lock))
return EPERM;
/* If the previous owner died and the caller did not succeed in
making the state consistent, mark the mutex as unrecoverable
and make all waiters. */
if (__builtin_expect (mutex->__data.__owner
== PTHREAD_MUTEX_INCONSISTENT, 0))
notrecoverable:
newowner = PTHREAD_MUTEX_NOTRECOVERABLE;
robust:
/* Remove mutex from the list. */
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
&mutex->__data.__list.__next);
/* We must set op_pending before we dequeue the mutex. Also see
comments at ENQUEUE_MUTEX. */
__asm ("" ::: "memory");
DEQUEUE_MUTEX (mutex);
mutex->__data.__owner = newowner;
if (decr)
/* One less user. */
--mutex->__data.__nusers;
/* Unlock by setting the lock to 0 (not acquired); if the lock had
FUTEX_WAITERS set previously, then wake any waiters.
The unlock operation must be the last access to the mutex to not
violate the mutex destruction requirements (see __lll_unlock). */
private = PTHREAD_ROBUST_MUTEX_PSHARED (mutex);
if (__glibc_unlikely ((atomic_exchange_release (&mutex->__data.__lock, 0)
& FUTEX_WAITERS) != 0))
futex_wake ((unsigned int *) &mutex->__data.__lock, 1, private);
/* We must clear op_pending after we release the mutex.
FIXME However, this violates the mutex destruction requirements
because another thread could acquire the mutex, destroy it, and
reuse the memory for something else; then, if this thread crashes,
and the memory happens to have a value equal to the TID, the kernel
will believe it is still related to the mutex (which has been
destroyed already) and will modify some other random object. */
__asm ("" ::: "memory");
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
break;
/* The PI support requires the Linux futex system call. If that's not
available, pthread_mutex_init should never have allowed the type to
be set. So it will get the default case for an invalid type. */
#ifdef __NR_futex
case PTHREAD_MUTEX_PI_RECURSIVE_NP:
/* Recursive mutex. */
if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid))
return EPERM;
if (--mutex->__data.__count != 0)
/* We still hold the mutex. */
return 0;
goto continue_pi_non_robust;
case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP:
/* Recursive mutex. */
if ((mutex->__data.__lock & FUTEX_TID_MASK)
== THREAD_GETMEM (THREAD_SELF, tid)
&& __builtin_expect (mutex->__data.__owner
== PTHREAD_MUTEX_INCONSISTENT, 0))
{
if (--mutex->__data.__count != 0)
/* We still hold the mutex. */
return ENOTRECOVERABLE;
goto pi_notrecoverable;
}
if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid))
return EPERM;
if (--mutex->__data.__count != 0)
/* We still hold the mutex. */
return 0;
goto continue_pi_robust;
case PTHREAD_MUTEX_PI_ERRORCHECK_NP:
case PTHREAD_MUTEX_PI_NORMAL_NP:
case PTHREAD_MUTEX_PI_ADAPTIVE_NP:
case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:
case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP:
if ((mutex->__data.__lock & FUTEX_TID_MASK)
!= THREAD_GETMEM (THREAD_SELF, tid)
|| ! lll_islocked (mutex->__data.__lock))
return EPERM;
/* If the previous owner died and the caller did not succeed in
making the state consistent, mark the mutex as unrecoverable
and make all waiters. */
/* See concurrency notes regarding __kind in struct __pthread_mutex_s
in sysdeps/nptl/bits/thread-shared-types.h. */
if ((atomic_load_relaxed (&(mutex->__data.__kind))
& PTHREAD_MUTEX_ROBUST_NORMAL_NP) != 0
&& __builtin_expect (mutex->__data.__owner
== PTHREAD_MUTEX_INCONSISTENT, 0))
pi_notrecoverable:
newowner = PTHREAD_MUTEX_NOTRECOVERABLE;
/* See concurrency notes regarding __kind in struct __pthread_mutex_s
in sysdeps/nptl/bits/thread-shared-types.h. */
if ((atomic_load_relaxed (&(mutex->__data.__kind))
& PTHREAD_MUTEX_ROBUST_NORMAL_NP) != 0)
{
continue_pi_robust:
/* Remove mutex from the list.
Note: robust PI futexes are signaled by setting bit 0. */
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
(void *) (((uintptr_t) &mutex->__data.__list.__next)
| 1));
/* We must set op_pending before we dequeue the mutex. Also see
comments at ENQUEUE_MUTEX. */
__asm ("" ::: "memory");
DEQUEUE_MUTEX (mutex);
}
continue_pi_non_robust:
mutex->__data.__owner = newowner;
if (decr)
/* One less user. */
--mutex->__data.__nusers;
/* Unlock. Load all necessary mutex data before releasing the mutex
to not violate the mutex destruction requirements (see
lll_unlock). */
/* See concurrency notes regarding __kind in struct __pthread_mutex_s
in sysdeps/nptl/bits/thread-shared-types.h. */
int robust = atomic_load_relaxed (&(mutex->__data.__kind))
& PTHREAD_MUTEX_ROBUST_NORMAL_NP;
private = (robust
? PTHREAD_ROBUST_MUTEX_PSHARED (mutex)
: PTHREAD_MUTEX_PSHARED (mutex));
/* Unlock the mutex using a CAS unless there are futex waiters or our
TID is not the value of __lock anymore, in which case we let the
kernel take care of the situation. Use release MO in the CAS to
synchronize with acquire MO in lock acquisitions. */
int l = atomic_load_relaxed (&mutex->__data.__lock);
do
{
if (((l & FUTEX_WAITERS) != 0)
|| (l != THREAD_GETMEM (THREAD_SELF, tid)))
{
futex_unlock_pi ((unsigned int *) &mutex->__data.__lock,
private);
break;
}
}
while (!atomic_compare_exchange_weak_release (&mutex->__data.__lock,
&l, 0));
/* This happens after the kernel releases the mutex but violates the
mutex destruction requirements; see comments in the code handling
PTHREAD_MUTEX_ROBUST_NORMAL_NP. */
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
break;
#endif /* __NR_futex. */
case PTHREAD_MUTEX_PP_RECURSIVE_NP:
/* Recursive mutex. */
if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid))
return EPERM;
if (--mutex->__data.__count != 0)
/* We still hold the mutex. */
return 0;
goto pp;
case PTHREAD_MUTEX_PP_ERRORCHECK_NP:
/* Error checking mutex. */
if (mutex->__data.__owner != THREAD_GETMEM (THREAD_SELF, tid)
|| (mutex->__data.__lock & ~ PTHREAD_MUTEX_PRIO_CEILING_MASK) == 0)
return EPERM;
/* FALLTHROUGH */
case PTHREAD_MUTEX_PP_NORMAL_NP:
case PTHREAD_MUTEX_PP_ADAPTIVE_NP:
/* Always reset the owner field. */
pp:
mutex->__data.__owner = 0;
if (decr)
/* One less user. */
--mutex->__data.__nusers;
/* Unlock. Use release MO in the CAS to synchronize with acquire MO in
lock acquisitions. */
int newval;
int oldval = atomic_load_relaxed (&mutex->__data.__lock);
do
{
newval = oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK;
}
while (!atomic_compare_exchange_weak_release (&mutex->__data.__lock,
&oldval, newval));
if ((oldval & ~PTHREAD_MUTEX_PRIO_CEILING_MASK) > 1)
futex_wake ((unsigned int *)&mutex->__data.__lock, 1,
PTHREAD_MUTEX_PSHARED (mutex));
int oldprio = newval >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
LIBC_PROBE (mutex_release, 1, mutex);
return __pthread_tpp_change_priority (oldprio, -1);
default:
/* Correct code cannot set any other type. */
return EINVAL;
}
LIBC_PROBE (mutex_release, 1, mutex);
return 0;
}
int
___pthread_mutex_unlock (pthread_mutex_t *mutex)
{
return __pthread_mutex_unlock_usercnt (mutex, 1);
}
libc_hidden_ver (___pthread_mutex_unlock, __pthread_mutex_unlock)
#ifndef SHARED
strong_alias (___pthread_mutex_unlock, __pthread_mutex_unlock)
#endif
versioned_symbol (libpthread, ___pthread_mutex_unlock, pthread_mutex_unlock,
GLIBC_2_0);
#if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_34)
compat_symbol (libpthread, ___pthread_mutex_unlock, __pthread_mutex_unlock,
GLIBC_2_0);
#endif