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Use private futexes for semaphores, unless they are initialized with pshared != 0.

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Change-Id: I534e36a7171cd37037ae03b910ba71ea6968286d
Note: previously, sem_init() would return an error if pshared != 0.
This commit is contained in:
David 'Digit' Turner
2010-06-02 18:12:12 -07:00
parent a8a2148863
commit 6304d8b218
4 changed files with 147 additions and 56 deletions
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63
libc/bionic/pthread.c
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@@ -43,7 +43,7 @@
#include <memory.h>
#include <assert.h>
#include <malloc.h>
#include <linux/futex.h>
#include <bionic_futex.h>
#include <cutils/atomic-inline.h>
#include <sys/prctl.h>
#include <sys/stat.h>
@@ -54,6 +54,16 @@ extern void _exit_with_stack_teardown(void * stackBase, int stackSize, int retCo
extern void _exit_thread(int retCode);
extern int __set_errno(int);
int __futex_wake_ex(volatile void *ftx, int pshared, int val)
{
return __futex_syscall3(ftx, pshared ? FUTEX_WAKE : FUTEX_WAKE_PRIVATE, val);
}
int __futex_wait_ex(volatile void *ftx, int pshared, int val, const struct timespec *timeout)
{
return __futex_syscall4(ftx, pshared ? FUTEX_WAIT : FUTEX_WAIT_PRIVATE, val, timeout);
}
#define __likely(cond) __builtin_expect(!!(cond), 1)
#define __unlikely(cond) __builtin_expect(!!(cond), 0)
@@ -716,24 +726,6 @@ int pthread_setschedparam(pthread_t thid, int policy,
}
int __futex_wait(volatile void *ftx, int val, const struct timespec *timeout);
int __futex_wake(volatile void *ftx, int count);
int __futex_syscall3(volatile void *ftx, int op, int val);
int __futex_syscall4(volatile void *ftx, int op, int val, const struct timespec *timeout);
#ifndef FUTEX_PRIVATE_FLAG
#define FUTEX_PRIVATE_FLAG 128
#endif
#ifndef FUTEX_WAIT_PRIVATE
#define FUTEX_WAIT_PRIVATE (FUTEX_WAIT|FUTEX_PRIVATE_FLAG)
#endif
#ifndef FUTEX_WAKE_PRIVATE
#define FUTEX_WAKE_PRIVATE (FUTEX_WAKE|FUTEX_PRIVATE_FLAG)
#endif
// mutex lock states
//
// 0: unlocked
@@ -935,10 +927,8 @@ _normal_lock(pthread_mutex_t* mutex)
* that the mutex is in state 2 when we go to sleep on it, which
* guarantees a wake-up call.
*/
int wait_op = shared ? FUTEX_WAIT : FUTEX_WAIT_PRIVATE;
while (__atomic_swap(shared|2, &mutex->value ) != (shared|0))
__futex_syscall4(&mutex->value, wait_op, shared|2, 0);
__futex_wait_ex(&mutex->value, shared, shared|2, 0);
}
ANDROID_MEMBAR_FULL();
}
@@ -961,7 +951,6 @@ _normal_unlock(pthread_mutex_t* mutex)
* if it wasn't 1 we have to do some additional work.
*/
if (__atomic_dec(&mutex->value) != (shared|1)) {
int wake_op = shared ? FUTEX_WAKE : FUTEX_WAKE_PRIVATE;
/*
* Start by releasing the lock. The decrement changed it from
* "contended lock" to "uncontended lock", which means we still
@@ -999,7 +988,7 @@ _normal_unlock(pthread_mutex_t* mutex)
* Either way we have correct behavior and nobody is orphaned on
* the wait queue.
*/
__futex_syscall3(&mutex->value, wake_op, 1);
__futex_wake_ex(&mutex->value, shared, 1);
}
}
@@ -1019,7 +1008,7 @@ _recursive_unlock(void)
int pthread_mutex_lock(pthread_mutex_t *mutex)
{
int mtype, tid, new_lock_type, shared, wait_op;
int mtype, tid, new_lock_type, shared;
if (__unlikely(mutex == NULL))
return EINVAL;
@@ -1064,8 +1053,7 @@ int pthread_mutex_lock(pthread_mutex_t *mutex)
new_lock_type = 1;
/* compute futex wait opcode and restore shared flag in mtype */
wait_op = shared ? FUTEX_WAIT : FUTEX_WAIT_PRIVATE;
mtype |= shared;
mtype |= shared;
for (;;) {
int oldv;
@@ -1091,7 +1079,7 @@ int pthread_mutex_lock(pthread_mutex_t *mutex)
*/
new_lock_type = 2;
__futex_syscall4(&mutex->value, wait_op, oldv, NULL);
__futex_wait_ex(&mutex->value, shared, oldv, NULL);
}
return 0;
}
@@ -1131,8 +1119,7 @@ int pthread_mutex_unlock(pthread_mutex_t *mutex)
/* Wake one waiting thread, if any */
if ((oldv & 3) == 2) {
int wake_op = shared ? FUTEX_WAKE : FUTEX_WAKE_PRIVATE;
__futex_syscall3(&mutex->value, wake_op, 1);
__futex_wake_ex(&mutex->value, shared, 1);
}
return 0;
}
@@ -1234,7 +1221,7 @@ int pthread_mutex_lock_timeout_np(pthread_mutex_t *mutex, unsigned msecs)
clockid_t clock = CLOCK_MONOTONIC;
struct timespec abstime;
struct timespec ts;
int mtype, tid, oldv, new_lock_type, shared, wait_op;
int mtype, tid, oldv, new_lock_type, shared;
/* compute absolute expiration time */
__timespec_to_relative_msec(&abstime, msecs, clock);
@@ -1248,8 +1235,6 @@ int pthread_mutex_lock_timeout_np(pthread_mutex_t *mutex, unsigned msecs)
/* Handle common case first */
if ( __likely(mtype == MUTEX_TYPE_NORMAL) )
{
int wait_op = shared ? FUTEX_WAIT : FUTEX_WAIT_PRIVATE;
/* fast path for uncontended lock */
if (__atomic_cmpxchg(shared|0, shared|1, &mutex->value) == 0) {
ANDROID_MEMBAR_FULL();
@@ -1261,7 +1246,7 @@ int pthread_mutex_lock_timeout_np(pthread_mutex_t *mutex, unsigned msecs)
if (__timespec_to_absolute(&ts, &abstime, clock) < 0)
return EBUSY;
__futex_syscall4(&mutex->value, wait_op, shared|2, &ts);
__futex_wait_ex(&mutex->value, shared, shared|2, &ts);
}
ANDROID_MEMBAR_FULL();
return 0;
@@ -1294,7 +1279,6 @@ int pthread_mutex_lock_timeout_np(pthread_mutex_t *mutex, unsigned msecs)
new_lock_type = 1;
/* Compute wait op and restore sharing bit in mtype */
wait_op = shared ? FUTEX_WAIT : FUTEX_WAIT_PRIVATE;
mtype |= shared;
for (;;) {
@@ -1325,7 +1309,7 @@ int pthread_mutex_lock_timeout_np(pthread_mutex_t *mutex, unsigned msecs)
if (__timespec_to_absolute(&ts, &abstime, clock) < 0)
return EBUSY;
__futex_syscall4(&mutex->value, wait_op, oldv, &ts);
__futex_wait_ex(&mutex->value, shared, oldv, &ts);
}
return 0;
}
@@ -1418,7 +1402,6 @@ static int
__pthread_cond_pulse(pthread_cond_t *cond, int counter)
{
long flags;
int wake_op;
if (__unlikely(cond == NULL))
return EINVAL;
@@ -1432,8 +1415,7 @@ __pthread_cond_pulse(pthread_cond_t *cond, int counter)
break;
}
wake_op = COND_IS_SHARED(cond) ? FUTEX_WAKE : FUTEX_WAKE_PRIVATE;
__futex_syscall3(&cond->value, wake_op, counter);
__futex_wake_ex(&cond->value, COND_IS_SHARED(cond), counter);
return 0;
}
@@ -1458,10 +1440,9 @@ int __pthread_cond_timedwait_relative(pthread_cond_t *cond,
{
int status;
int oldvalue = cond->value;
int wait_op = COND_IS_SHARED(cond) ? FUTEX_WAIT : FUTEX_WAIT_PRIVATE;
pthread_mutex_unlock(mutex);
status = __futex_syscall4(&cond->value, wait_op, oldvalue, reltime);
status = __futex_wait_ex(&cond->value, COND_IS_SHARED(cond), oldvalue, reltime);
pthread_mutex_lock(mutex);
if (status == (-ETIMEDOUT)) return ETIMEDOUT;