glibc/nptl/pthread_mutex_lock.c
Florian Weimer 8ec022a037 nptl: Remove GLIBC_2.34 versions of __pthread_mutex_lock, __pthread_mutex_unlock
Now that there are no internal users anymore, these new symbol
versions can be removed from the public ABI.  The compatibility
symbols remain.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
2021-07-07 08:41:17 +02:00

645 lines
20 KiB
C

/* Copyright (C) 2002-2021 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
<https://www.gnu.org/licenses/>. */
#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/param.h>
#include <not-cancel.h>
#include "pthreadP.h"
#include <atomic.h>
#include <futex-internal.h>
#include <stap-probe.h>
#include <shlib-compat.h>
/* Some of the following definitions differ when pthread_mutex_cond_lock.c
includes this file. */
#ifndef LLL_MUTEX_LOCK
/* lll_lock with single-thread optimization. */
static inline void
lll_mutex_lock_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. If the lock is already marked as
acquired, POSIX requires that pthread_mutex_lock deadlocks for
normal mutexes, so skip the optimization in that case as
well. */
int private = PTHREAD_MUTEX_PSHARED (mutex);
if (private == LLL_PRIVATE && SINGLE_THREAD_P && mutex->__data.__lock == 0)
mutex->__data.__lock = 1;
else
lll_lock (mutex->__data.__lock, private);
}
# define LLL_MUTEX_LOCK(mutex) \
lll_lock ((mutex)->__data.__lock, PTHREAD_MUTEX_PSHARED (mutex))
# define LLL_MUTEX_LOCK_OPTIMIZED(mutex) lll_mutex_lock_optimized (mutex)
# define LLL_MUTEX_TRYLOCK(mutex) \
lll_trylock ((mutex)->__data.__lock)
# define LLL_ROBUST_MUTEX_LOCK_MODIFIER 0
# define LLL_MUTEX_LOCK_ELISION(mutex) \
lll_lock_elision ((mutex)->__data.__lock, (mutex)->__data.__elision, \
PTHREAD_MUTEX_PSHARED (mutex))
# define LLL_MUTEX_TRYLOCK_ELISION(mutex) \
lll_trylock_elision((mutex)->__data.__lock, (mutex)->__data.__elision, \
PTHREAD_MUTEX_PSHARED (mutex))
# define PTHREAD_MUTEX_LOCK ___pthread_mutex_lock
# define PTHREAD_MUTEX_VERSIONS 1
#endif
static int __pthread_mutex_lock_full (pthread_mutex_t *mutex)
__attribute_noinline__;
int
PTHREAD_MUTEX_LOCK (pthread_mutex_t *mutex)
{
/* See concurrency notes regarding mutex type which is loaded from __kind
in struct __pthread_mutex_s in sysdeps/nptl/bits/thread-shared-types.h. */
unsigned int type = PTHREAD_MUTEX_TYPE_ELISION (mutex);
LIBC_PROBE (mutex_entry, 1, mutex);
if (__builtin_expect (type & ~(PTHREAD_MUTEX_KIND_MASK_NP
| PTHREAD_MUTEX_ELISION_FLAGS_NP), 0))
return __pthread_mutex_lock_full (mutex);
if (__glibc_likely (type == PTHREAD_MUTEX_TIMED_NP))
{
FORCE_ELISION (mutex, goto elision);
simple:
/* Normal mutex. */
LLL_MUTEX_LOCK_OPTIMIZED (mutex);
assert (mutex->__data.__owner == 0);
}
#if ENABLE_ELISION_SUPPORT
else if (__glibc_likely (type == PTHREAD_MUTEX_TIMED_ELISION_NP))
{
elision: __attribute__((unused))
/* This case can never happen on a system without elision,
as the mutex type initialization functions will not
allow to set the elision flags. */
/* Don't record owner or users for elision case. This is a
tail call. */
return LLL_MUTEX_LOCK_ELISION (mutex);
}
#endif
else if (__builtin_expect (PTHREAD_MUTEX_TYPE (mutex)
== PTHREAD_MUTEX_RECURSIVE_NP, 1))
{
/* Recursive mutex. */
pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
/* 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;
}
/* We have to get the mutex. */
LLL_MUTEX_LOCK_OPTIMIZED (mutex);
assert (mutex->__data.__owner == 0);
mutex->__data.__count = 1;
}
else if (__builtin_expect (PTHREAD_MUTEX_TYPE (mutex)
== PTHREAD_MUTEX_ADAPTIVE_NP, 1))
{
if (LLL_MUTEX_TRYLOCK (mutex) != 0)
{
int cnt = 0;
int max_cnt = MIN (max_adaptive_count (),
mutex->__data.__spins * 2 + 10);
do
{
if (cnt++ >= max_cnt)
{
LLL_MUTEX_LOCK (mutex);
break;
}
atomic_spin_nop ();
}
while (LLL_MUTEX_TRYLOCK (mutex) != 0);
mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8;
}
assert (mutex->__data.__owner == 0);
}
else
{
pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
assert (PTHREAD_MUTEX_TYPE (mutex) == PTHREAD_MUTEX_ERRORCHECK_NP);
/* Check whether we already hold the mutex. */
if (__glibc_unlikely (mutex->__data.__owner == id))
return EDEADLK;
goto simple;
}
pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
/* Record the ownership. */
mutex->__data.__owner = id;
#ifndef NO_INCR
++mutex->__data.__nusers;
#endif
LIBC_PROBE (mutex_acquired, 1, mutex);
return 0;
}
static int
__pthread_mutex_lock_full (pthread_mutex_t *mutex)
{
int oldval;
pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
switch (PTHREAD_MUTEX_TYPE (mutex))
{
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);
/* We need to set op_pending before starting the operation. Also
see comments at ENQUEUE_MUTEX. */
__asm ("" ::: "memory");
oldval = mutex->__data.__lock;
/* This is set to FUTEX_WAITERS iff we might have shared the
FUTEX_WAITERS flag with other threads, and therefore need to keep it
set to avoid lost wake-ups. We have the same requirement in the
simple mutex algorithm.
We start with value zero for a normal mutex, and FUTEX_WAITERS if we
are building the special case mutexes for use from within condition
variables. */
unsigned int assume_other_futex_waiters = LLL_ROBUST_MUTEX_LOCK_MODIFIER;
while (1)
{
/* Try to acquire the lock through a CAS from 0 (not acquired) to
our TID | assume_other_futex_waiters. */
if (__glibc_likely (oldval == 0))
{
oldval
= atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
id | assume_other_futex_waiters, 0);
if (__glibc_likely (oldval == 0))
break;
}
if ((oldval & FUTEX_OWNER_DIED) != 0)
{
/* The previous owner died. Try locking the mutex. */
int newval = id;
#ifdef NO_INCR
/* We are not taking assume_other_futex_waiters into accoount
here simply because we'll set FUTEX_WAITERS anyway. */
newval |= FUTEX_WAITERS;
#else
newval |= (oldval & FUTEX_WAITERS) | assume_other_futex_waiters;
#endif
newval
= atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
newval, oldval);
if (newval != oldval)
{
oldval = newval;
continue;
}
/* We got the mutex. */
mutex->__data.__count = 1;
/* But it is inconsistent unless marked otherwise. */
mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
/* We must not enqueue the mutex before we have acquired it.
Also see comments at ENQUEUE_MUTEX. */
__asm ("" ::: "memory");
ENQUEUE_MUTEX (mutex);
/* We need to clear op_pending after we enqueue the mutex. */
__asm ("" ::: "memory");
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. If we are not supposed
to increment __nusers we actually have to decrement
it here. */
#ifdef NO_INCR
--mutex->__data.__nusers;
#endif
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)
{
/* We do not need to ensure ordering wrt another memory
access. Also see comments at ENQUEUE_MUTEX. */
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
NULL);
return EDEADLK;
}
if (kind == PTHREAD_MUTEX_ROBUST_RECURSIVE_NP)
{
/* We do not need to ensure ordering wrt another memory
access. */
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;
}
}
/* We cannot acquire the mutex nor has its owner died. Thus, try
to block using futexes. Set FUTEX_WAITERS if necessary so that
other threads are aware that there are potentially threads
blocked on the futex. Restart if oldval changed in the
meantime. */
if ((oldval & FUTEX_WAITERS) == 0)
{
if (atomic_compare_and_exchange_bool_acq (&mutex->__data.__lock,
oldval | FUTEX_WAITERS,
oldval)
!= 0)
{
oldval = mutex->__data.__lock;
continue;
}
oldval |= FUTEX_WAITERS;
}
/* It is now possible that we share the FUTEX_WAITERS flag with
another thread; therefore, update assume_other_futex_waiters so
that we do not forget about this when handling other cases
above and thus do not cause lost wake-ups. */
assume_other_futex_waiters |= FUTEX_WAITERS;
/* Block using the futex and reload current lock value. */
futex_wait ((unsigned int *) &mutex->__data.__lock, oldval,
PTHREAD_ROBUST_MUTEX_PSHARED (mutex));
oldval = mutex->__data.__lock;
}
/* We have acquired the mutex; check if it is still consistent. */
if (__builtin_expect (mutex->__data.__owner
== PTHREAD_MUTEX_NOTRECOVERABLE, 0))
{
/* This mutex is now not recoverable. */
mutex->__data.__count = 0;
int private = PTHREAD_ROBUST_MUTEX_PSHARED (mutex);
lll_unlock (mutex->__data.__lock, private);
/* FIXME This violates the mutex destruction requirements. See
__pthread_mutex_unlock_full. */
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
return ENOTRECOVERABLE;
}
mutex->__data.__count = 1;
/* We must not enqueue the mutex before we have acquired it.
Also see comments at ENQUEUE_MUTEX. */
__asm ("" ::: "memory");
ENQUEUE_MUTEX (mutex);
/* We need to clear op_pending after we enqueue the mutex. */
__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:
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, robust;
{
/* See concurrency notes regarding __kind in struct __pthread_mutex_s
in sysdeps/nptl/bits/thread-shared-types.h. */
int mutex_kind = atomic_load_relaxed (&(mutex->__data.__kind));
kind = mutex_kind & PTHREAD_MUTEX_KIND_MASK_NP;
robust = mutex_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));
/* We need to set op_pending before starting the operation. Also
see comments at ENQUEUE_MUTEX. */
__asm ("" ::: "memory");
}
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)
{
/* We do not need to ensure ordering wrt another memory
access. */
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
return EDEADLK;
}
if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
{
/* We do not need to ensure ordering wrt another memory
access. */
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;
}
}
int newval = id;
# ifdef NO_INCR
newval |= FUTEX_WAITERS;
# endif
oldval = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
newval, 0);
if (oldval != 0)
{
/* The mutex is locked. The kernel will now take care of
everything. */
int private = (robust
? PTHREAD_ROBUST_MUTEX_PSHARED (mutex)
: PTHREAD_MUTEX_PSHARED (mutex));
int e = futex_lock_pi64 (&mutex->__data.__lock, NULL, private);
if (e == ESRCH || e == EDEADLK)
{
assert (e != EDEADLK
|| (kind != PTHREAD_MUTEX_ERRORCHECK_NP
&& kind != PTHREAD_MUTEX_RECURSIVE_NP));
/* ESRCH can happen only for non-robust PI mutexes where
the owner of the lock died. */
assert (e != ESRCH || !robust);
/* Delay the thread indefinitely. */
while (1)
__futex_abstimed_wait64 (&(unsigned int){0}, 0,
0 /* ignored */, NULL, private);
}
oldval = mutex->__data.__lock;
assert (robust || (oldval & FUTEX_OWNER_DIED) == 0);
}
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;
/* We must not enqueue the mutex before we have acquired it.
Also see comments at ENQUEUE_MUTEX. */
__asm ("" ::: "memory");
ENQUEUE_MUTEX_PI (mutex);
/* We need to clear op_pending after we enqueue the mutex. */
__asm ("" ::: "memory");
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. If we are not supposed to
increment __nusers we actually have to decrement it here. */
# ifdef NO_INCR
--mutex->__data.__nusers;
# endif
return EOWNERDEAD;
}
if (robust
&& __builtin_expect (mutex->__data.__owner
== PTHREAD_MUTEX_NOTRECOVERABLE, 0))
{
/* This mutex is now not recoverable. */
mutex->__data.__count = 0;
futex_unlock_pi ((unsigned int *) &mutex->__data.__lock,
PTHREAD_ROBUST_MUTEX_PSHARED (mutex));
/* To the kernel, this will be visible after the kernel has
acquired the mutex in the syscall. */
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
return ENOTRECOVERABLE;
}
mutex->__data.__count = 1;
if (robust)
{
/* We must not enqueue the mutex before we have acquired it.
Also see comments at ENQUEUE_MUTEX. */
__asm ("" ::: "memory");
ENQUEUE_MUTEX_PI (mutex);
/* We need to clear op_pending after we enqueue the mutex. */
__asm ("" ::: "memory");
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
}
}
break;
#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:
{
/* See concurrency notes regarding __kind in struct __pthread_mutex_s
in sysdeps/nptl/bits/thread-shared-types.h. */
int kind = atomic_load_relaxed (&(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,
#ifdef NO_INCR
ceilval | 2,
#else
ceilval | 1,
#endif
ceilval);
if (oldval == ceilval)
break;
do
{
oldval
= atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
ceilval | 2,
ceilval | 1);
if ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval)
break;
if (oldval != ceilval)
futex_wait ((unsigned int * ) &mutex->__data.__lock,
ceilval | 2,
PTHREAD_MUTEX_PSHARED (mutex));
}
while (atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
ceilval | 2, ceilval)
!= ceilval);
}
while ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval);
assert (mutex->__data.__owner == 0);
mutex->__data.__count = 1;
}
break;
default:
/* Correct code cannot set any other type. */
return EINVAL;
}
/* Record the ownership. */
mutex->__data.__owner = id;
#ifndef NO_INCR
++mutex->__data.__nusers;
#endif
LIBC_PROBE (mutex_acquired, 1, mutex);
return 0;
}
#if PTHREAD_MUTEX_VERSIONS
libc_hidden_ver (___pthread_mutex_lock, __pthread_mutex_lock)
# ifndef SHARED
strong_alias (___pthread_mutex_lock, __pthread_mutex_lock)
# endif
versioned_symbol (libpthread, ___pthread_mutex_lock, pthread_mutex_lock,
GLIBC_2_0);
# if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_34)
compat_symbol (libpthread, ___pthread_mutex_lock, __pthread_mutex_lock,
GLIBC_2_0);
# endif
#endif /* PTHREAD_MUTEX_VERSIONS */
#ifdef NO_INCR
void
__pthread_mutex_cond_lock_adjust (pthread_mutex_t *mutex)
{
/* See concurrency notes regarding __kind in struct __pthread_mutex_s
in sysdeps/nptl/bits/thread-shared-types.h. */
int mutex_kind = atomic_load_relaxed (&(mutex->__data.__kind));
assert ((mutex_kind & PTHREAD_MUTEX_PRIO_INHERIT_NP) != 0);
assert ((mutex_kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP) == 0);
assert ((mutex_kind & PTHREAD_MUTEX_PSHARED_BIT) == 0);
/* Record the ownership. */
pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
mutex->__data.__owner = id;
if (mutex_kind == PTHREAD_MUTEX_PI_RECURSIVE_NP)
++mutex->__data.__count;
}
#endif