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glibc/nptl/pthread_mutex_trylock.c
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/* Copyright (C) 2002-2016 Free Software Foundation, Inc. | |
This file is part of the GNU C Library. | |
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002. | |
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 <assert.h> | |
#include <errno.h> | |
#include <stdlib.h> | |
#include "pthreadP.h" | |
#include <lowlevellock.h> | |
#ifndef lll_trylock_elision | |
#define lll_trylock_elision(a,t) lll_trylock(a) | |
#endif | |
#ifndef FORCE_ELISION | |
#define FORCE_ELISION(m, s) | |
#endif | |
int | |
__pthread_mutex_trylock (pthread_mutex_t *mutex) | |
{ | |
int oldval; | |
pid_t id = THREAD_GETMEM (THREAD_SELF, tid); | |
switch (__builtin_expect (PTHREAD_MUTEX_TYPE_ELISION (mutex), | |
PTHREAD_MUTEX_TIMED_NP)) | |
{ | |
/* Recursive mutex. */ | |
case PTHREAD_MUTEX_RECURSIVE_NP|PTHREAD_MUTEX_ELISION_NP: | |
case PTHREAD_MUTEX_RECURSIVE_NP: | |
/* Check whether we already hold the mutex. */ | |
if (mutex->__data.__owner == id) | |
{ | |
/* Just bump the counter. */ | |
if (__glibc_unlikely (mutex->__data.__count + 1 == 0)) | |
/* Overflow of the counter. */ | |
return EAGAIN; | |
++mutex->__data.__count; | |
return 0; | |
} | |
if (lll_trylock (mutex->__data.__lock) == 0) | |
{ | |
/* Record the ownership. */ | |
mutex->__data.__owner = id; | |
mutex->__data.__count = 1; | |
++mutex->__data.__nusers; | |
return 0; | |
} | |
break; | |
case PTHREAD_MUTEX_TIMED_ELISION_NP: | |
elision: __attribute__((unused)) | |
if (lll_trylock_elision (mutex->__data.__lock, | |
mutex->__data.__elision) != 0) | |
break; | |
/* Don't record the ownership. */ | |
return 0; | |
case PTHREAD_MUTEX_TIMED_NP: | |
FORCE_ELISION (mutex, goto elision); | |
/*FALL THROUGH*/ | |
case PTHREAD_MUTEX_ADAPTIVE_NP: | |
case PTHREAD_MUTEX_ERRORCHECK_NP: | |
if (lll_trylock (mutex->__data.__lock) != 0) | |
break; | |
/* Record the ownership. */ | |
mutex->__data.__owner = id; | |
++mutex->__data.__nusers; | |
return 0; | |
case PTHREAD_MUTEX_ROBUST_RECURSIVE_NP: | |
case PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP: | |
case PTHREAD_MUTEX_ROBUST_NORMAL_NP: | |
case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP: | |
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, | |
&mutex->__data.__list.__next); | |
oldval = mutex->__data.__lock; | |
do | |
{ | |
again: | |
if ((oldval & FUTEX_OWNER_DIED) != 0) | |
{ | |
/* The previous owner died. Try locking the mutex. */ | |
int newval = id | (oldval & FUTEX_WAITERS); | |
newval | |
= atomic_compare_and_exchange_val_acq (&mutex->__data.__lock, | |
newval, oldval); | |
if (newval != oldval) | |
{ | |
oldval = newval; | |
goto again; | |
} | |
/* We got the mutex. */ | |
mutex->__data.__count = 1; | |
/* But it is inconsistent unless marked otherwise. */ | |
mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT; | |
ENQUEUE_MUTEX (mutex); | |
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); | |
/* Note that we deliberately exist here. If we fall | |
through to the end of the function __nusers would be | |
incremented which is not correct because the old | |
owner has to be discounted. */ | |
return EOWNERDEAD; | |
} | |
/* Check whether we already hold the mutex. */ | |
if (__glibc_unlikely ((oldval & FUTEX_TID_MASK) == id)) | |
{ | |
int kind = PTHREAD_MUTEX_TYPE (mutex); | |
if (kind == PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP) | |
{ | |
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, | |
NULL); | |
return EDEADLK; | |
} | |
if (kind == PTHREAD_MUTEX_ROBUST_RECURSIVE_NP) | |
{ | |
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, | |
NULL); | |
/* Just bump the counter. */ | |
if (__glibc_unlikely (mutex->__data.__count + 1 == 0)) | |
/* Overflow of the counter. */ | |
return EAGAIN; | |
++mutex->__data.__count; | |
return 0; | |
} | |
} | |
oldval = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock, | |
id, 0); | |
if (oldval != 0 && (oldval & FUTEX_OWNER_DIED) == 0) | |
{ | |
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); | |
return EBUSY; | |
} | |
if (__builtin_expect (mutex->__data.__owner | |
== PTHREAD_MUTEX_NOTRECOVERABLE, 0)) | |
{ | |
/* This mutex is now not recoverable. */ | |
mutex->__data.__count = 0; | |
if (oldval == id) | |
lll_unlock (mutex->__data.__lock, | |
PTHREAD_ROBUST_MUTEX_PSHARED (mutex)); | |
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); | |
return ENOTRECOVERABLE; | |
} | |
} | |
while ((oldval & FUTEX_OWNER_DIED) != 0); | |
ENQUEUE_MUTEX (mutex); | |
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); | |
mutex->__data.__owner = id; | |
++mutex->__data.__nusers; | |
mutex->__data.__count = 1; | |
return 0; | |
/* 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: | |
case PTHREAD_MUTEX_PI_ERRORCHECK_NP: | |
case PTHREAD_MUTEX_PI_NORMAL_NP: | |
case PTHREAD_MUTEX_PI_ADAPTIVE_NP: | |
case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP: | |
case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP: | |
case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP: | |
case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP: | |
{ | |
int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP; | |
int robust = mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP; | |
if (robust) | |
/* 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)); | |
oldval = mutex->__data.__lock; | |
/* Check whether we already hold the mutex. */ | |
if (__glibc_unlikely ((oldval & FUTEX_TID_MASK) == id)) | |
{ | |
if (kind == PTHREAD_MUTEX_ERRORCHECK_NP) | |
{ | |
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); | |
return EDEADLK; | |
} | |
if (kind == PTHREAD_MUTEX_RECURSIVE_NP) | |
{ | |
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); | |
/* Just bump the counter. */ | |
if (__glibc_unlikely (mutex->__data.__count + 1 == 0)) | |
/* Overflow of the counter. */ | |
return EAGAIN; | |
++mutex->__data.__count; | |
return 0; | |
} | |
} | |
oldval | |
= atomic_compare_and_exchange_val_acq (&mutex->__data.__lock, | |
id, 0); | |
if (oldval != 0) | |
{ | |
if ((oldval & FUTEX_OWNER_DIED) == 0) | |
{ | |
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); | |
return EBUSY; | |
} | |
assert (robust); | |
/* The mutex owner died. The kernel will now take care of | |
everything. */ | |
int private = (robust | |
? PTHREAD_ROBUST_MUTEX_PSHARED (mutex) | |
: PTHREAD_MUTEX_PSHARED (mutex)); | |
INTERNAL_SYSCALL_DECL (__err); | |
int e = INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock, | |
__lll_private_flag (FUTEX_TRYLOCK_PI, | |
private), 0, 0); | |
if (INTERNAL_SYSCALL_ERROR_P (e, __err) | |
&& INTERNAL_SYSCALL_ERRNO (e, __err) == EWOULDBLOCK) | |
{ | |
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); | |
return EBUSY; | |
} | |
oldval = mutex->__data.__lock; | |
} | |
if (__glibc_unlikely (oldval & FUTEX_OWNER_DIED)) | |
{ | |
atomic_and (&mutex->__data.__lock, ~FUTEX_OWNER_DIED); | |
/* We got the mutex. */ | |
mutex->__data.__count = 1; | |
/* But it is inconsistent unless marked otherwise. */ | |
mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT; | |
ENQUEUE_MUTEX (mutex); | |
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); | |
/* Note that we deliberately exit here. If we fall | |
through to the end of the function __nusers would be | |
incremented which is not correct because the old owner | |
has to be discounted. */ | |
return EOWNERDEAD; | |
} | |
if (robust | |
&& __builtin_expect (mutex->__data.__owner | |
== PTHREAD_MUTEX_NOTRECOVERABLE, 0)) | |
{ | |
/* This mutex is now not recoverable. */ | |
mutex->__data.__count = 0; | |
INTERNAL_SYSCALL_DECL (__err); | |
INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock, | |
__lll_private_flag (FUTEX_UNLOCK_PI, | |
PTHREAD_ROBUST_MUTEX_PSHARED (mutex)), | |
0, 0); | |
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); | |
return ENOTRECOVERABLE; | |
} | |
if (robust) | |
{ | |
ENQUEUE_MUTEX_PI (mutex); | |
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL); | |
} | |
mutex->__data.__owner = id; | |
++mutex->__data.__nusers; | |
mutex->__data.__count = 1; | |
return 0; | |
} | |
#endif /* __NR_futex. */ | |
case PTHREAD_MUTEX_PP_RECURSIVE_NP: | |
case PTHREAD_MUTEX_PP_ERRORCHECK_NP: | |
case PTHREAD_MUTEX_PP_NORMAL_NP: | |
case PTHREAD_MUTEX_PP_ADAPTIVE_NP: | |
{ | |
int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP; | |
oldval = mutex->__data.__lock; | |
/* Check whether we already hold the mutex. */ | |
if (mutex->__data.__owner == id) | |
{ | |
if (kind == PTHREAD_MUTEX_ERRORCHECK_NP) | |
return EDEADLK; | |
if (kind == PTHREAD_MUTEX_RECURSIVE_NP) | |
{ | |
/* Just bump the counter. */ | |
if (__glibc_unlikely (mutex->__data.__count + 1 == 0)) | |
/* Overflow of the counter. */ | |
return EAGAIN; | |
++mutex->__data.__count; | |
return 0; | |
} | |
} | |
int oldprio = -1, ceilval; | |
do | |
{ | |
int ceiling = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) | |
>> PTHREAD_MUTEX_PRIO_CEILING_SHIFT; | |
if (__pthread_current_priority () > ceiling) | |
{ | |
if (oldprio != -1) | |
__pthread_tpp_change_priority (oldprio, -1); | |
return EINVAL; | |
} | |
int retval = __pthread_tpp_change_priority (oldprio, ceiling); | |
if (retval) | |
return retval; | |
ceilval = ceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT; | |
oldprio = ceiling; | |
oldval | |
= atomic_compare_and_exchange_val_acq (&mutex->__data.__lock, | |
ceilval | 1, ceilval); | |
if (oldval == ceilval) | |
break; | |
} | |
while ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval); | |
if (oldval != ceilval) | |
{ | |
__pthread_tpp_change_priority (oldprio, -1); | |
break; | |
} | |
assert (mutex->__data.__owner == 0); | |
/* Record the ownership. */ | |
mutex->__data.__owner = id; | |
++mutex->__data.__nusers; | |
mutex->__data.__count = 1; | |
return 0; | |
} | |
break; | |
default: | |
/* Correct code cannot set any other type. */ | |
return EINVAL; | |
} | |
return EBUSY; | |
} | |
#ifndef __pthread_mutex_trylock | |
#ifndef pthread_mutex_trylock | |
strong_alias (__pthread_mutex_trylock, pthread_mutex_trylock) | |
#endif | |
#endif |