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-rw-r--r--libc/bionic/pthread.c791
1 files changed, 493 insertions, 298 deletions
diff --git a/libc/bionic/pthread.c b/libc/bionic/pthread.c
index c1a6a8a..6a63868 100644
--- a/libc/bionic/pthread.c
+++ b/libc/bionic/pthread.c
@@ -44,6 +44,9 @@
#include <assert.h>
#include <malloc.h>
+#define __likely(cond) __builtin_expect(!!(cond), 1)
+#define __unlikely(cond) __builtin_expect(!!(cond), 0)
+
extern int __pthread_clone(int (*fn)(void*), void *child_stack, int flags, void *arg);
extern void _exit_with_stack_teardown(void * stackBase, int stackSize, int retCode);
extern void _exit_thread(int retCode);
@@ -712,6 +715,9 @@ 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_wait_private(volatile void *ftx, int val, const struct timespec *timeout);
+int __futex_wake_private(volatile void *ftx, int count);
+
// mutex lock states
//
// 0: unlocked
@@ -723,7 +729,8 @@ int __futex_wake(volatile void *ftx, int count);
* bits: name description
* 31-16 tid owner thread's kernel id (recursive and errorcheck only)
* 15-14 type mutex type
- * 13-2 counter counter of recursive mutexes
+ * 13 sharing sharing flag
+ * 12-2 counter counter of recursive mutexes
* 1-0 state lock state (0, 1 or 2)
*/
@@ -737,10 +744,21 @@ int __futex_wake(volatile void *ftx, int count);
#define MUTEX_TYPE_ERRORCHECK 0x8000
#define MUTEX_COUNTER_SHIFT 2
-#define MUTEX_COUNTER_MASK 0x3ffc
+#define MUTEX_COUNTER_MASK 0x1ffc
+#define MUTEX_SHARING_MASK 0x2000
+#define MUTEX_IS_SHARED(m) (((m)->value & MUTEX_SHARING_MASK) != 0)
+/* A mutex attribute stores the following in its fields:
+ *
+ * bits: name description
+ * 0-3 type type of thread (NORMAL/RECURSIVE/ERRORCHECK)
+ * 4 sharing 1 if shared, or 0 otherwise.
+ */
+
+#define MUTEXATTR_TYPE_MASK 0x0007
+#define MUTEXATTR_SHARING_MASK 0x0010
int pthread_mutexattr_init(pthread_mutexattr_t *attr)
{
@@ -764,10 +782,12 @@ int pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
int pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *type)
{
- if (attr && *attr >= PTHREAD_MUTEX_NORMAL &&
- *attr <= PTHREAD_MUTEX_ERRORCHECK ) {
- *type = *attr;
- return 0;
+ if (attr) {
+ int atype = (*attr & MUTEXATTR_TYPE_MASK);
+ if (atype >= PTHREAD_MUTEX_NORMAL && atype <= PTHREAD_MUTEX_ERRORCHECK) {
+ *type = atype;
+ return 0;
+ }
}
return EINVAL;
}
@@ -776,7 +796,7 @@ int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type)
{
if (attr && type >= PTHREAD_MUTEX_NORMAL &&
type <= PTHREAD_MUTEX_ERRORCHECK ) {
- *attr = type;
+ *attr = (*attr & ~MUTEXATTR_TYPE_MASK) | type;
return 0;
}
return EINVAL;
@@ -791,54 +811,70 @@ int pthread_mutexattr_setpshared(pthread_mutexattr_t *attr, int pshared)
switch (pshared) {
case PTHREAD_PROCESS_PRIVATE:
+ *attr &= ~MUTEXATTR_SHARING_MASK;
+ return 0;
+
case PTHREAD_PROCESS_SHARED:
/* our current implementation of pthread actually supports shared
* mutexes but won't cleanup if a process dies with the mutex held.
* Nevertheless, it's better than nothing. Shared mutexes are used
* by surfaceflinger and audioflinger.
*/
+ *attr |= MUTEXATTR_SHARING_MASK;
return 0;
}
- return ENOTSUP;
+ return EINVAL;
}
int pthread_mutexattr_getpshared(pthread_mutexattr_t *attr, int *pshared)
{
- if (!attr)
+ if (!attr || !pshared)
return EINVAL;
- *pshared = PTHREAD_PROCESS_PRIVATE;
+ *pshared = (*attr & MUTEXATTR_SHARING_MASK) ? PTHREAD_PROCESS_SHARED
+ : PTHREAD_PROCESS_PRIVATE;
return 0;
}
int pthread_mutex_init(pthread_mutex_t *mutex,
const pthread_mutexattr_t *attr)
{
- if ( mutex ) {
- if (attr == NULL) {
- mutex->value = MUTEX_TYPE_NORMAL;
- return 0;
- }
- switch ( *attr ) {
- case PTHREAD_MUTEX_NORMAL:
- mutex->value = MUTEX_TYPE_NORMAL;
- return 0;
+ int value = 0;
- case PTHREAD_MUTEX_RECURSIVE:
- mutex->value = MUTEX_TYPE_RECURSIVE;
- return 0;
+ if (__unlikely(mutex == NULL))
+ return EINVAL;
- case PTHREAD_MUTEX_ERRORCHECK:
- mutex->value = MUTEX_TYPE_ERRORCHECK;
- return 0;
- }
+ if (__likely(attr == NULL)) {
+ mutex->value = MUTEX_TYPE_NORMAL;
+ return 0;
}
- return EINVAL;
+
+ if ((*attr & MUTEXATTR_SHARING_MASK) != 0)
+ value |= MUTEX_SHARING_MASK;
+
+ switch (*attr & MUTEXATTR_TYPE_MASK) {
+ case PTHREAD_MUTEX_NORMAL:
+ value |= MUTEX_TYPE_NORMAL;
+ break;
+ case PTHREAD_MUTEX_RECURSIVE:
+ value |= MUTEX_TYPE_RECURSIVE;
+ break;
+ case PTHREAD_MUTEX_ERRORCHECK:
+ value |= MUTEX_TYPE_ERRORCHECK;
+ break;
+ default:
+ return EINVAL;
+ }
+ mutex->value = value;
+ return 0;
}
int pthread_mutex_destroy(pthread_mutex_t *mutex)
{
+ if (__unlikely(mutex == NULL))
+ return EINVAL;
+
mutex->value = 0xdead10cc;
return 0;
}
@@ -855,35 +891,46 @@ int pthread_mutex_destroy(pthread_mutex_t *mutex)
* Non-recursive mutexes don't use the thread-id or counter fields, and the
* "type" value is zero, so the only bits that will be set are the ones in
* the lock state field.
+ *
+ * This routine is used for both shared and private mutexes.
*/
static __inline__ void
_normal_lock(pthread_mutex_t* mutex)
{
- /*
- * The common case is an unlocked mutex, so we begin by trying to
- * change the lock's state from 0 to 1. __atomic_cmpxchg() returns 0
- * if it made the swap successfully. If the result is nonzero, this
- * lock is already held by another thread.
- */
- if (__atomic_cmpxchg(0, 1, &mutex->value ) != 0) {
+ if (__likely(!MUTEX_IS_SHARED(mutex))) {
/*
- * We want to go to sleep until the mutex is available, which
- * requires promoting it to state 2. We need to swap in the new
- * state value and then wait until somebody wakes us up.
- *
- * __atomic_swap() returns the previous value. We swap 2 in and
- * see if we got zero back; if so, we have acquired the lock. If
- * not, another thread still holds the lock and we wait again.
- *
- * The second argument to the __futex_wait() call is compared
- * against the current value. If it doesn't match, __futex_wait()
- * returns immediately (otherwise, it sleeps for a time specified
- * by the third argument; 0 means sleep forever). This ensures
- * that the mutex is in state 2 when we go to sleep on it, which
- * guarantees a wake-up call.
- */
- while (__atomic_swap(2, &mutex->value ) != 0)
- __futex_wait(&mutex->value, 2, 0);
+ * The common case is an unlocked mutex, so we begin by trying to
+ * change the lock's state from 0 to 1. __atomic_cmpxchg() returns 0
+ * if it made the swap successfully. If the result is nonzero, this
+ * lock is already held by another thread.
+ */
+ if (__atomic_cmpxchg(0, 1, &mutex->value) != 0) {
+ /*
+ * We want to go to sleep until the mutex is available, which
+ * requires promoting it to state 2. We need to swap in the new
+ * state value and then wait until somebody wakes us up.
+ *
+ * __atomic_swap() returns the previous value. We swap 2 in and
+ * see if we got zero back; if so, we have acquired the lock. If
+ * not, another thread still holds the lock and we wait again.
+ *
+ * The second argument to the __futex_wait() call is compared
+ * against the current value. If it doesn't match, __futex_wait()
+ * returns immediately (otherwise, it sleeps for a time specified
+ * by the third argument; 0 means sleep forever). This ensures
+ * that the mutex is in state 2 when we go to sleep on it, which
+ * guarantees a wake-up call.
+ */
+ while (__atomic_swap(2, &mutex->value ) != 0)
+ __futex_wait_private(&mutex->value, 2, 0);
+ }
+ } else {
+ /* Same algorithm, with the sharing bit flag set */
+ const int sharing = MUTEX_SHARING_MASK;
+ if (__atomic_cmpxchg(sharing|0, sharing|1, &mutex->value) != 0) {
+ while (__atomic_swap(sharing|2, &mutex->value ) != (sharing|0))
+ __futex_wait(&mutex->value, sharing|2, 0);
+ }
}
}
@@ -894,50 +941,59 @@ _normal_lock(pthread_mutex_t* mutex)
static __inline__ void
_normal_unlock(pthread_mutex_t* mutex)
{
- /*
- * The mutex value will be 1 or (rarely) 2. We use an atomic decrement
- * to release the lock. __atomic_dec() returns the previous value;
- * if it wasn't 1 we have to do some additional work.
- */
- if (__atomic_dec(&mutex->value) != 1) {
+ if (__likely(!MUTEX_IS_SHARED(mutex))) {
/*
- * Start by releasing the lock. The decrement changed it from
- * "contended lock" to "uncontended lock", which means we still
- * hold it, and anybody who tries to sneak in will push it back
- * to state 2.
- *
- * Once we set it to zero the lock is up for grabs. We follow
- * this with a __futex_wake() to ensure that one of the waiting
- * threads has a chance to grab it.
- *
- * This doesn't cause a race with the swap/wait pair in
- * _normal_lock(), because the __futex_wait() call there will
- * return immediately if the mutex value isn't 2.
- */
- mutex->value = 0;
-
- /*
- * Wake up one waiting thread. We don't know which thread will be
- * woken or when it'll start executing -- futexes make no guarantees
- * here. There may not even be a thread waiting.
- *
- * The newly-woken thread will replace the 0 we just set above
- * with 2, which means that when it eventually releases the mutex
- * it will also call FUTEX_WAKE. This results in one extra wake
- * call whenever a lock is contended, but lets us avoid forgetting
- * anyone without requiring us to track the number of sleepers.
- *
- * It's possible for another thread to sneak in and grab the lock
- * between the zero assignment above and the wake call below. If
- * the new thread is "slow" and holds the lock for a while, we'll
- * wake up a sleeper, which will swap in a 2 and then go back to
- * sleep since the lock is still held. If the new thread is "fast",
- * running to completion before we call wake, the thread we
- * eventually wake will find an unlocked mutex and will execute.
- * Either way we have correct behavior and nobody is orphaned on
- * the wait queue.
- */
- __futex_wake(&mutex->value, 1);
+ * The mutex value will be 1 or (rarely) 2. We use an atomic decrement
+ * to release the lock. __atomic_dec() returns the previous value;
+ * if it wasn't 1 we have to do some additional work.
+ */
+ if (__atomic_dec(&mutex->value) != 1) {
+ /*
+ * Start by releasing the lock. The decrement changed it from
+ * "contended lock" to "uncontended lock", which means we still
+ * hold it, and anybody who tries to sneak in will push it back
+ * to state 2.
+ *
+ * Once we set it to zero the lock is up for grabs. We follow
+ * this with a __futex_wake() to ensure that one of the waiting
+ * threads has a chance to grab it.
+ *
+ * This doesn't cause a race with the swap/wait pair in
+ * _normal_lock(), because the __futex_wait() call there will
+ * return immediately if the mutex value isn't 2.
+ */
+ mutex->value = 0;
+
+ /*
+ * Wake up one waiting thread. We don't know which thread will be
+ * woken or when it'll start executing -- futexes make no guarantees
+ * here. There may not even be a thread waiting.
+ *
+ * The newly-woken thread will replace the 0 we just set above
+ * with 2, which means that when it eventually releases the mutex
+ * it will also call FUTEX_WAKE. This results in one extra wake
+ * call whenever a lock is contended, but lets us avoid forgetting
+ * anyone without requiring us to track the number of sleepers.
+ *
+ * It's possible for another thread to sneak in and grab the lock
+ * between the zero assignment above and the wake call below. If
+ * the new thread is "slow" and holds the lock for a while, we'll
+ * wake up a sleeper, which will swap in a 2 and then go back to
+ * sleep since the lock is still held. If the new thread is "fast",
+ * running to completion before we call wake, the thread we
+ * eventually wake will find an unlocked mutex and will execute.
+ * Either way we have correct behavior and nobody is orphaned on
+ * the wait queue.
+ */
+ __futex_wake_private(&mutex->value, 1);
+ }
+ } else {
+ /* Same algorithm with sharing bit flag set */
+ const int sharing = MUTEX_SHARING_MASK;
+ if (__atomic_dec(&mutex->value) != (sharing|1)) {
+ mutex->value = sharing;
+ __futex_wake(&mutex->value, 1);
+ }
}
}
@@ -955,173 +1011,200 @@ _recursive_unlock(void)
_normal_unlock( &__recursive_lock );
}
-#define __likely(cond) __builtin_expect(!!(cond), 1)
-#define __unlikely(cond) __builtin_expect(!!(cond), 0)
-
int pthread_mutex_lock(pthread_mutex_t *mutex)
{
- if (__likely(mutex != NULL))
+ int mtype, tid, new_lock_type, sharing;
+
+ if (__unlikely(mutex == NULL))
+ return EINVAL;
+
+ /* get mutex type */
+ mtype = (mutex->value & MUTEX_TYPE_MASK);
+
+ /* Handle normal mutexes quickly */
+ if ( __likely(mtype == MUTEX_TYPE_NORMAL) ) {
+ _normal_lock(mutex);
+ return 0;
+ }
+
+ /* This is a recursive or error check mutex.
+ * Check that we don't already own it.
+ */
+ tid = __get_thread()->kernel_id;
+ if ( tid == MUTEX_OWNER(mutex) )
{
- int mtype = (mutex->value & MUTEX_TYPE_MASK);
+ int oldv, counter;
- if ( __likely(mtype == MUTEX_TYPE_NORMAL) ) {
- _normal_lock(mutex);
+ if (mtype == MUTEX_TYPE_ERRORCHECK) {
+ /* trying to re-lock a mutex we already acquired */
+ return EDEADLK;
}
- else
- {
- int tid = __get_thread()->kernel_id;
+ /*
+ * We own the mutex, but other threads are able to change
+ * the contents (e.g. promoting it to "contended"), so we
+ * need to hold the global lock.
+ */
+ _recursive_lock();
+ oldv = mutex->value;
+ counter = (oldv + (1 << MUTEX_COUNTER_SHIFT)) & MUTEX_COUNTER_MASK;
+ mutex->value = (oldv & ~MUTEX_COUNTER_MASK) | counter;
+ _recursive_unlock();
- if ( tid == MUTEX_OWNER(mutex) )
- {
- int oldv, counter;
+ return 0;
+ }
- if (mtype == MUTEX_TYPE_ERRORCHECK) {
- /* trying to re-lock a mutex we already acquired */
- return EDEADLK;
- }
- /*
- * We own the mutex, but other threads are able to change
- * the contents (e.g. promoting it to "contended"), so we
- * need to hold the global lock.
- */
- _recursive_lock();
- oldv = mutex->value;
- counter = (oldv + (1 << MUTEX_COUNTER_SHIFT)) & MUTEX_COUNTER_MASK;
- mutex->value = (oldv & ~MUTEX_COUNTER_MASK) | counter;
- _recursive_unlock();
- }
- else
- {
- /*
- * If the new lock is available immediately, we grab it in
- * the "uncontended" state.
- */
- int new_lock_type = 1;
-
- for (;;) {
- int oldv;
-
- _recursive_lock();
- oldv = mutex->value;
- if (oldv == mtype) { /* uncontended released lock => 1 or 2 */
- mutex->value = ((tid << 16) | mtype | new_lock_type);
- } else if ((oldv & 3) == 1) { /* locked state 1 => state 2 */
- oldv ^= 3;
- mutex->value = oldv;
- }
- _recursive_unlock();
-
- if (oldv == mtype)
- break;
-
- /*
- * The lock was held, possibly contended by others. From
- * now on, if we manage to acquire the lock, we have to
- * assume that others are still contending for it so that
- * we'll wake them when we unlock it.
- */
- new_lock_type = 2;
-
- __futex_wait( &mutex->value, oldv, 0 );
- }
- }
+ /* We don't own it, try to lock it.
+ * If the new lock is available immediately, we grab it in
+ * the "uncontended" state.
+ */
+ new_lock_type = 1;
+ sharing = (mutex->value & MUTEX_SHARING_MASK);
+
+ mtype |= sharing; /* restore sharing bit flag */
+
+ /* here, mtype corresponds to the uncontended value for the mutex,
+ * i.e. something like:
+ *
+ * <tid=0><type=?><sharing=?><counter=0><state=0>
+ */
+
+ for (;;) {
+ int oldv;
+
+ _recursive_lock();
+ oldv = mutex->value;
+ if (oldv == mtype) { /* uncontended released lock => 1 or 2 */
+ mutex->value = ((tid << 16) | mtype | new_lock_type);
+ } else if ((oldv & 3) == 1) { /* locked state 1 => state 2 */
+ oldv ^= 3;
+ mutex->value = oldv;
+ }
+ _recursive_unlock();
+
+ if (oldv == mtype)
+ break;
+
+ /*
+ * The lock was held, possibly contended by others. From
+ * now on, if we manage to acquire the lock, we have to
+ * assume that others are still contending for it so that
+ * we'll wake them when we unlock it.
+ */
+ new_lock_type = 2;
+
+ if (sharing) {
+ __futex_wait(&mutex->value, oldv, 0);
+ } else {
+ __futex_wait_private(&mutex->value, oldv, 0);
}
- return 0;
}
- return EINVAL;
+ return 0;
}
int pthread_mutex_unlock(pthread_mutex_t *mutex)
{
- if (__likely(mutex != NULL))
- {
- int mtype = (mutex->value & MUTEX_TYPE_MASK);
+ int mtype, tid, sharing, oldv;
- if (__likely(mtype == MUTEX_TYPE_NORMAL)) {
- _normal_unlock(mutex);
- }
- else
- {
- int tid = __get_thread()->kernel_id;
+ if (__unlikely(mutex == NULL))
+ return EINVAL;
- if ( tid == MUTEX_OWNER(mutex) )
- {
- int oldv;
-
- _recursive_lock();
- oldv = mutex->value;
- if (oldv & MUTEX_COUNTER_MASK) {
- mutex->value = oldv - (1 << MUTEX_COUNTER_SHIFT);
- oldv = 0;
- } else {
- mutex->value = mtype;
- }
- _recursive_unlock();
+ mtype = (mutex->value & MUTEX_TYPE_MASK);
- if ((oldv & 3) == 2)
- __futex_wake( &mutex->value, 1 );
- }
- else {
- /* trying to unlock a lock we do not own */
- return EPERM;
- }
- }
+ if (__likely(mtype == MUTEX_TYPE_NORMAL)) {
+ _normal_unlock(mutex);
return 0;
}
- return EINVAL;
+
+ tid = __get_thread()->kernel_id;
+ sharing = (mutex->value & MUTEX_SHARING_MASK);
+
+ mtype |= sharing; /* restore sharing bit flag */
+
+ /* ensure that we own the mutex */
+ if (__unlikely(tid != MUTEX_OWNER(mutex)))
+ return EPERM;
+
+ /* decrement or unlock it */
+ _recursive_lock();
+ oldv = mutex->value;
+ if (oldv & MUTEX_COUNTER_MASK) {
+ /* decrement non-0 counter */
+ mutex->value = oldv - (1 << MUTEX_COUNTER_SHIFT);
+ oldv = 0;
+ } else {
+ /* counter was 0, revert to uncontended value */
+ mutex->value = mtype;
+ }
+ _recursive_unlock();
+
+ /* if the mutex was contended, wake one waiting thread */
+ if ((oldv & 3) == 2) {
+ if (sharing) {
+ __futex_wake(&mutex->value, 1);
+ } else {
+ __futex_wake_private(&mutex->value, 1);
+ }
+ }
+ return 0;
}
int pthread_mutex_trylock(pthread_mutex_t *mutex)
{
- if (__likely(mutex != NULL))
- {
- int mtype = (mutex->value & MUTEX_TYPE_MASK);
+ int mtype, sharing, tid, oldv;
- if ( __likely(mtype == MUTEX_TYPE_NORMAL) )
- {
- if (__atomic_cmpxchg(0, 1, &mutex->value) == 0)
- return 0;
+ if (__unlikely(mutex == NULL))
+ return EINVAL;
- return EBUSY;
- }
- else
- {
- int tid = __get_thread()->kernel_id;
- int oldv;
+ mtype = (mutex->value & MUTEX_TYPE_MASK);
- if ( tid == MUTEX_OWNER(mutex) )
- {
- int oldv, counter;
+ /* handle normal mutex first */
+ if ( __likely(mtype == MUTEX_TYPE_NORMAL) )
+ {
+ int sharing = (mutex->value & MUTEX_SHARING_MASK);
- if (mtype == MUTEX_TYPE_ERRORCHECK) {
- /* already locked by ourselves */
- return EDEADLK;
- }
+ if (__atomic_cmpxchg(sharing|0, sharing|1, &mutex->value) == 0)
+ return 0;
- _recursive_lock();
- oldv = mutex->value;
- counter = (oldv + (1 << MUTEX_COUNTER_SHIFT)) & MUTEX_COUNTER_MASK;
- mutex->value = (oldv & ~MUTEX_COUNTER_MASK) | counter;
- _recursive_unlock();
- return 0;
- }
+ return EBUSY;
+ }
- /* try to lock it */
- _recursive_lock();
- oldv = mutex->value;
- if (oldv == mtype) /* uncontended released lock => state 1 */
- mutex->value = ((tid << 16) | mtype | 1);
- _recursive_unlock();
+ /* recursive or errorcheck mutex, do we already own it ? */
+ tid = __get_thread()->kernel_id;
+ sharing = mutex->value & MUTEX_SHARING_MASK;
- if (oldv != mtype)
- return EBUSY;
+ if ( tid == MUTEX_OWNER(mutex) )
+ {
+ int counter;
- return 0;
+ if (mtype == MUTEX_TYPE_ERRORCHECK) {
+ /* already locked by ourselves */
+ return EDEADLK;
}
+
+ _recursive_lock();
+ oldv = mutex->value;
+ counter = (oldv + (1 << MUTEX_COUNTER_SHIFT)) & MUTEX_COUNTER_MASK;
+ mutex->value = (oldv & ~MUTEX_COUNTER_MASK) | counter;
+ _recursive_unlock();
+ return 0;
}
- return EINVAL;
+
+ /* we don't own it, so try to get it */
+ mtype |= sharing;
+
+ /* try to lock it */
+ _recursive_lock();
+ oldv = mutex->value;
+ if (oldv == mtype) /* uncontended released lock => state 1 */
+ mutex->value = ((tid << 16) | mtype | 1);
+ _recursive_unlock();
+
+ if (oldv != mtype)
+ return EBUSY;
+
+ return 0;
}
@@ -1164,16 +1247,21 @@ 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, sharing, new_lock_type;
/* compute absolute expiration time */
__timespec_to_relative_msec(&abstime, msecs, clock);
- if (__likely(mutex != NULL))
- {
- int mtype = (mutex->value & MUTEX_TYPE_MASK);
+ if (__unlikely(mutex == NULL))
+ return EINVAL;
+
- if ( __likely(mtype == MUTEX_TYPE_NORMAL) )
- {
+ /* handle normal mutexes first */
+ mtype = (mutex->value & MUTEX_TYPE_MASK);
+
+ if ( __likely(mtype == MUTEX_TYPE_NORMAL) )
+ {
+ if (__likely(!MUTEX_IS_SHARED(mutex))) {
/* fast path for unconteded lock */
if (__atomic_cmpxchg(0, 1, &mutex->value) == 0)
return 0;
@@ -1183,77 +1271,125 @@ int pthread_mutex_lock_timeout_np(pthread_mutex_t *mutex, unsigned msecs)
if (__timespec_to_absolute(&ts, &abstime, clock) < 0)
return EBUSY;
- __futex_wait(&mutex->value, 2, &ts);
+ __futex_wait_private(&mutex->value, 2, &ts);
+ }
+ } else /* sharing */ {
+ const int sharing = MUTEX_SHARING_MASK;
+ if (__atomic_cmpxchg(sharing|0, sharing|1, &mutex->value) == 0)
+ return 0;
+
+ /* loop while needed */
+ while (__atomic_swap(sharing|2, &mutex->value) != (sharing|0)) {
+ if (__timespec_to_absolute(&ts, &abstime, clock) < 0)
+ return EBUSY;
+
+ __futex_wait(&mutex->value, sharing|2, &ts);
}
- return 0;
}
- else
- {
- int tid = __get_thread()->kernel_id;
- int oldv;
+ return 0;
+ }
- if ( tid == MUTEX_OWNER(mutex) )
- {
- int oldv, counter;
+ /* recursive or errorcheck - do we own the mutex ? */
+ tid = __get_thread()->kernel_id;
- if (mtype == MUTEX_TYPE_ERRORCHECK) {
- /* already locked by ourselves */
- return EDEADLK;
- }
+ if ( tid == MUTEX_OWNER(mutex) )
+ {
+ int counter;
- _recursive_lock();
- oldv = mutex->value;
- counter = (oldv + (1 << MUTEX_COUNTER_SHIFT)) & MUTEX_COUNTER_MASK;
- mutex->value = (oldv & ~MUTEX_COUNTER_MASK) | counter;
- _recursive_unlock();
- return 0;
- }
- else
- {
- /*
- * If the new lock is available immediately, we grab it in
- * the "uncontended" state.
- */
- int new_lock_type = 1;
-
- for (;;) {
- int oldv;
- struct timespec ts;
-
- _recursive_lock();
- oldv = mutex->value;
- if (oldv == mtype) { /* uncontended released lock => 1 or 2 */
- mutex->value = ((tid << 16) | mtype | new_lock_type);
- } else if ((oldv & 3) == 1) { /* locked state 1 => state 2 */
- oldv ^= 3;
- mutex->value = oldv;
- }
- _recursive_unlock();
-
- if (oldv == mtype)
- break;
-
- /*
- * The lock was held, possibly contended by others. From
- * now on, if we manage to acquire the lock, we have to
- * assume that others are still contending for it so that
- * we'll wake them when we unlock it.
- */
- new_lock_type = 2;
-
- if (__timespec_to_absolute(&ts, &abstime, clock) < 0)
- return EBUSY;
-
- __futex_wait( &mutex->value, oldv, &ts );
- }
- return 0;
- }
+ if (mtype == MUTEX_TYPE_ERRORCHECK) {
+ /* already locked by ourselves */
+ return EDEADLK;
}
+
+ _recursive_lock();
+ oldv = mutex->value;
+ counter = (oldv + (1 << MUTEX_COUNTER_SHIFT)) & MUTEX_COUNTER_MASK;
+ mutex->value = (oldv & ~MUTEX_COUNTER_MASK) | counter;
+ _recursive_unlock();
+ return 0;
}
- return EINVAL;
+
+ /* we don't own it, try to lock it */
+ new_lock_type = 1;
+ sharing = (mutex->value & MUTEX_SHARING_MASK);
+
+ mtype |= sharing;
+
+ for (;;) {
+ struct timespec ts;
+
+ _recursive_lock();
+ oldv = mutex->value;
+ if (oldv == mtype) { /* uncontended released lock => 1 or 2 */
+ mutex->value = ((tid << 16) | mtype | new_lock_type);
+ } else if ((oldv & 3) == 1) { /* locked state 1 => state 2 */
+ oldv ^= 3;
+ mutex->value = oldv;
+ }
+ _recursive_unlock();
+
+ if (oldv == mtype)
+ break;
+
+ /*
+ * The lock was held, possibly contended by others. From
+ * now on, if we manage to acquire the lock, we have to
+ * assume that others are still contending for it so that
+ * we'll wake them when we unlock it.
+ */
+ new_lock_type = 2;
+
+ if (__timespec_to_absolute(&ts, &abstime, clock) < 0)
+ return EBUSY;
+
+ if (sharing) {
+ __futex_wait(&mutex->value, oldv, &ts);
+ } else {
+ __futex_wait_private(&mutex->value, oldv, &ts);
+ }
+ }
+ return 0;
}
+int
+pthread_condattr_init(pthread_condattr_t *attr)
+{
+ *attr = PTHREAD_PROCESS_PRIVATE;
+ return 0;
+}
+
+int
+pthread_condattr_setpshared(pthread_condattr_t *attr, int pshared)
+{
+ if (attr == NULL)
+ return EINVAL;
+
+ if (pshared != PTHREAD_PROCESS_PRIVATE &&
+ pshared != PTHREAD_PROCESS_SHARED)
+ return EINVAL;
+
+ *attr = pshared;
+ return 0;
+}
+
+int
+pthread_condattr_getpshared(pthread_condattr_t *attr, int *pshared)
+{
+ if (attr == NULL || pshared == NULL)
+ return EINVAL;
+
+ *pshared = *attr;
+ return 0;
+}
+
+int
+pthread_condattr_destroy(pthread_condattr_t *attr)
+{
+ *attr = 0xdeada11d;
+ return 0;
+}
+
/* XXX *technically* there is a race condition that could allow
* XXX a signal to be missed. If thread A is preempted in _wait()
* XXX after unlocking the mutex and before waiting, and if other
@@ -1262,10 +1398,29 @@ int pthread_mutex_lock_timeout_np(pthread_mutex_t *mutex, unsigned msecs)
* XXX then the signal will be lost.
*/
+/* Condition variables:
+ * bits name description
+ * 0 sharing 1 if process-shared, 0 if private
+ * 2-31 counter counter increment on each signal/broadcast
+ */
+
+#define COND_SHARING_MASK 0x0001
+#define COND_COUNTER_INCREMENT 0x0002
+#define COND_COUNTER_MASK (~COND_SHARING_MASK)
+
+#define COND_IS_SHARED(cond) (((cond)->value & COND_SHARING_MASK) != 0)
+
int pthread_cond_init(pthread_cond_t *cond,
const pthread_condattr_t *attr)
{
+ if (cond == NULL)
+ return EINVAL;
+
cond->value = 0;
+
+ if (attr != NULL && *attr == PTHREAD_PROCESS_SHARED)
+ cond->value |= COND_SHARING_MASK;
+
return 0;
}
@@ -1275,17 +1430,53 @@ int pthread_cond_destroy(pthread_cond_t *cond)
return 0;
}
+/* This function is used by pthread_cond_broadcast and
+ * pthread_cond_signal to 'pulse' the condition variable.
+ *
+ * This means atomically decrementing the counter value
+ * while leaving the other bits untouched.
+ */
+static void
+__pthread_cond_pulse(pthread_cond_t *cond)
+{
+ long flags = (cond->value & ~COND_COUNTER_MASK);
+
+ for (;;) {
+ long oldval = cond->value;
+ long newval = ((oldval - COND_COUNTER_INCREMENT) & COND_COUNTER_MASK) | flags;
+ if (__atomic_cmpxchg(oldval, newval, &cond->value) == 0)
+ break;
+ }
+}
+
int pthread_cond_broadcast(pthread_cond_t *cond)
{
- __atomic_dec(&cond->value);
- __futex_wake(&cond->value, INT_MAX);
+ if (cond == NULL)
+ return EINVAL;
+
+ __pthread_cond_pulse(cond);
+
+ if (COND_IS_SHARED(cond)) {
+ __futex_wake(&cond->value, INT_MAX);
+ } else {
+ __futex_wake_private(&cond->value, INT_MAX);
+ }
+
return 0;
}
int pthread_cond_signal(pthread_cond_t *cond)
{
- __atomic_dec(&cond->value);
- __futex_wake(&cond->value, 1);
+ if (cond == NULL)
+ return EINVAL;
+
+ __pthread_cond_pulse(cond);
+
+ if (COND_IS_SHARED(cond)) {
+ __futex_wake(&cond->value, 1);
+ } else {
+ __futex_wake_private(&cond->value, 1);
+ }
return 0;
}
@@ -1302,7 +1493,11 @@ int __pthread_cond_timedwait_relative(pthread_cond_t *cond,
int oldvalue = cond->value;
pthread_mutex_unlock(mutex);
- status = __futex_wait(&cond->value, oldvalue, reltime);
+ if (COND_IS_SHARED(cond)) {
+ status = __futex_wait(&cond->value, oldvalue, reltime);
+ } else {
+ status = __futex_wait_private(&cond->value, oldvalue, reltime);
+ }
pthread_mutex_lock(mutex);
if (status == (-ETIMEDOUT)) return ETIMEDOUT;
generated by cgit v1.1 at 2024-12-23 03:35:09 +0000