Hide content of pthread_cond_t in pthread_cond_internal_t.
Bug: 19249079 Change-Id: I6f55af30bcd6211ce71630c6cacbef0e1663dcee
This commit is contained in:
Yabin Cui
parent
d2cf59d463
commit
32651b8e8e
@ -41,6 +41,13 @@
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#include "private/bionic_time_conversions.h"
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#include "private/bionic_tls.h"
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// XXX *technically* there is a race condition that could allow
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// XXX a signal to be missed. If thread A is preempted in _wait()
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// XXX after unlocking the mutex and before waiting, and if other
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// XXX threads call signal or broadcast UINT_MAX/2 times (exactly),
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// XXX before thread A is scheduled again and calls futex_wait(),
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// XXX then the signal will be lost.
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// We use one bit in pthread_condattr_t (long) values as the 'shared' flag
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// and one bit for the clock type (CLOCK_REALTIME is ((clockid_t) 1), and
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// CLOCK_MONOTONIC is ((clockid_t) 0).). The rest of the bits are a counter.
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@ -57,7 +64,6 @@
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#define COND_GET_CLOCK(c) (((c) & COND_CLOCK_MASK) >> 1)
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#define COND_SET_CLOCK(attr, c) ((attr) | (c << 1))
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int pthread_condattr_init(pthread_condattr_t* attr) {
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*attr = 0;
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*attr |= PTHREAD_PROCESS_PRIVATE;
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@ -98,47 +104,50 @@ int pthread_condattr_destroy(pthread_condattr_t* attr) {
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return 0;
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}
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static inline atomic_uint* COND_TO_ATOMIC_POINTER(pthread_cond_t* cond) {
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static_assert(sizeof(atomic_uint) == sizeof(cond->value),
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"cond->value should actually be atomic_uint in implementation.");
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struct pthread_cond_internal_t {
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atomic_uint state;
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// We prefer casting to atomic_uint instead of declaring cond->value to be atomic_uint directly.
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// Because using the second method pollutes pthread.h, and causes an error when compiling libcxx.
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return reinterpret_cast<atomic_uint*>(&cond->value);
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bool process_shared() const {
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return COND_IS_SHARED(atomic_load_explicit(&state, memory_order_relaxed));
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}
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int get_clock() const {
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return COND_GET_CLOCK(atomic_load_explicit(&state, memory_order_relaxed));
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}
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#if defined(__LP64__)
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char __reserved[44];
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#endif
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};
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static pthread_cond_internal_t* __get_internal_cond(pthread_cond_t* cond_interface) {
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static_assert(sizeof(pthread_cond_t) == sizeof(pthread_cond_internal_t),
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"pthread_cond_t should actually be pthread_cond_internal_t in implementation.");
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return reinterpret_cast<pthread_cond_internal_t*>(cond_interface);
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}
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// XXX *technically* there is a race condition that could allow
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// XXX a signal to be missed. If thread A is preempted in _wait()
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// XXX after unlocking the mutex and before waiting, and if other
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// XXX threads call signal or broadcast UINT_MAX/2 times (exactly),
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// XXX before thread A is scheduled again and calls futex_wait(),
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// XXX then the signal will be lost.
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int pthread_cond_init(pthread_cond_t* cond, const pthread_condattr_t* attr) {
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atomic_uint* cond_value_ptr = COND_TO_ATOMIC_POINTER(cond);
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unsigned int init_value = 0;
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int pthread_cond_init(pthread_cond_t* cond_interface, const pthread_condattr_t* attr) {
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pthread_cond_internal_t* cond = __get_internal_cond(cond_interface);
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unsigned int init_state = 0;
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if (attr != NULL) {
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init_value = (*attr & COND_FLAGS_MASK);
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init_state = (*attr & COND_FLAGS_MASK);
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}
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atomic_init(cond_value_ptr, init_value);
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atomic_init(&cond->state, init_state);
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return 0;
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}
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int pthread_cond_destroy(pthread_cond_t* cond) {
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atomic_uint* cond_value_ptr = COND_TO_ATOMIC_POINTER(cond);
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atomic_store_explicit(cond_value_ptr, 0xdeadc04d, memory_order_relaxed);
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int pthread_cond_destroy(pthread_cond_t* cond_interface) {
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pthread_cond_internal_t* cond = __get_internal_cond(cond_interface);
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atomic_store_explicit(&cond->state, 0xdeadc04d, memory_order_relaxed);
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return 0;
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}
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// This function is used by pthread_cond_broadcast and
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// pthread_cond_signal to atomically decrement the counter
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// then wake up thread_count threads.
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static int __pthread_cond_pulse(atomic_uint* cond_value_ptr, int thread_count) {
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unsigned int old_value = atomic_load_explicit(cond_value_ptr, memory_order_relaxed);
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bool shared = COND_IS_SHARED(old_value);
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static int __pthread_cond_pulse(pthread_cond_internal_t* cond, int thread_count) {
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// We don't use a release/seq_cst fence here. Because pthread_cond_wait/signal can't be
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// used as a method for memory synchronization by itself. It should always be used with
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// pthread mutexes. Note that Spurious wakeups from pthread_cond_wait/timedwait may occur,
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@ -149,20 +158,18 @@ static int __pthread_cond_pulse(atomic_uint* cond_value_ptr, int thread_count) {
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// synchronization. And it doesn't help even if we use any fence here.
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// The increase of value should leave flags alone, even if the value can overflows.
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atomic_fetch_add_explicit(cond_value_ptr, COND_COUNTER_STEP, memory_order_relaxed);
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atomic_fetch_add_explicit(&cond->state, COND_COUNTER_STEP, memory_order_relaxed);
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__futex_wake_ex(cond_value_ptr, shared, thread_count);
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__futex_wake_ex(&cond->state, cond->process_shared(), thread_count);
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return 0;
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}
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__LIBC_HIDDEN__
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int __pthread_cond_timedwait_relative(atomic_uint* cond_value_ptr, pthread_mutex_t* mutex,
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const timespec* reltime) {
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unsigned int old_value = atomic_load_explicit(cond_value_ptr, memory_order_relaxed);
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bool shared = COND_IS_SHARED(old_value);
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static int __pthread_cond_timedwait_relative(pthread_cond_internal_t* cond, pthread_mutex_t* mutex,
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const timespec* rel_timeout_or_null) {
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unsigned int old_state = atomic_load_explicit(&cond->state, memory_order_relaxed);
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pthread_mutex_unlock(mutex);
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int status = __futex_wait_ex(cond_value_ptr, shared, old_value, reltime);
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int status = __futex_wait_ex(&cond->state, cond->process_shared(), old_state, rel_timeout_or_null);
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pthread_mutex_lock(mutex);
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if (status == -ETIMEDOUT) {
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@ -171,67 +178,68 @@ int __pthread_cond_timedwait_relative(atomic_uint* cond_value_ptr, pthread_mutex
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return 0;
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}
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__LIBC_HIDDEN__
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int __pthread_cond_timedwait(atomic_uint* cond_value_ptr, pthread_mutex_t* mutex,
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const timespec* abs_ts, clockid_t clock) {
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static int __pthread_cond_timedwait(pthread_cond_internal_t* cond, pthread_mutex_t* mutex,
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const timespec* abs_timeout_or_null, clockid_t clock) {
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timespec ts;
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timespec* tsp;
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timespec* rel_timeout = NULL;
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if (abs_ts != NULL) {
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if (!timespec_from_absolute_timespec(ts, *abs_ts, clock)) {
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if (abs_timeout_or_null != NULL) {
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rel_timeout = &ts;
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if (!timespec_from_absolute_timespec(*rel_timeout, *abs_timeout_or_null, clock)) {
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return ETIMEDOUT;
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}
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tsp = &ts;
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} else {
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tsp = NULL;
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}
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return __pthread_cond_timedwait_relative(cond_value_ptr, mutex, tsp);
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return __pthread_cond_timedwait_relative(cond, mutex, rel_timeout);
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}
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int pthread_cond_broadcast(pthread_cond_t* cond) {
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atomic_uint* cond_value_ptr = COND_TO_ATOMIC_POINTER(cond);
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return __pthread_cond_pulse(cond_value_ptr, INT_MAX);
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int pthread_cond_broadcast(pthread_cond_t* cond_interface) {
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return __pthread_cond_pulse(__get_internal_cond(cond_interface), INT_MAX);
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}
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int pthread_cond_signal(pthread_cond_t* cond) {
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atomic_uint* cond_value_ptr = COND_TO_ATOMIC_POINTER(cond);
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return __pthread_cond_pulse(cond_value_ptr, 1);
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int pthread_cond_signal(pthread_cond_t* cond_interface) {
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return __pthread_cond_pulse(__get_internal_cond(cond_interface), 1);
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}
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int pthread_cond_wait(pthread_cond_t* cond, pthread_mutex_t* mutex) {
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atomic_uint* cond_value_ptr = COND_TO_ATOMIC_POINTER(cond);
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return __pthread_cond_timedwait(cond_value_ptr, mutex, NULL,
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COND_GET_CLOCK(atomic_load_explicit(cond_value_ptr, memory_order_relaxed)));
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int pthread_cond_wait(pthread_cond_t* cond_interface, pthread_mutex_t* mutex) {
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pthread_cond_internal_t* cond = __get_internal_cond(cond_interface);
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return __pthread_cond_timedwait(cond, mutex, NULL, cond->get_clock());
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}
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int pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t * mutex, const timespec *abstime) {
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atomic_uint* cond_value_ptr = COND_TO_ATOMIC_POINTER(cond);
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return __pthread_cond_timedwait(cond_value_ptr, mutex, abstime,
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COND_GET_CLOCK(atomic_load_explicit(cond_value_ptr, memory_order_relaxed)));
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int pthread_cond_timedwait(pthread_cond_t *cond_interface, pthread_mutex_t * mutex,
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const timespec *abstime) {
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pthread_cond_internal_t* cond = __get_internal_cond(cond_interface);
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return __pthread_cond_timedwait(cond, mutex, abstime, cond->get_clock());
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}
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#if !defined(__LP64__)
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// TODO: this exists only for backward binary compatibility on 32 bit platforms.
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extern "C" int pthread_cond_timedwait_monotonic(pthread_cond_t* cond, pthread_mutex_t* mutex, const timespec* abstime) {
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atomic_uint* cond_value_ptr = COND_TO_ATOMIC_POINTER(cond);
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return __pthread_cond_timedwait(cond_value_ptr, mutex, abstime, CLOCK_MONOTONIC);
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extern "C" int pthread_cond_timedwait_monotonic(pthread_cond_t* cond_interface,
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pthread_mutex_t* mutex,
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const timespec* abs_timeout) {
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return __pthread_cond_timedwait(__get_internal_cond(cond_interface), mutex, abs_timeout,
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CLOCK_MONOTONIC);
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}
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extern "C" int pthread_cond_timedwait_monotonic_np(pthread_cond_t* cond, pthread_mutex_t* mutex, const timespec* abstime) {
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atomic_uint* cond_value_ptr = COND_TO_ATOMIC_POINTER(cond);
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return __pthread_cond_timedwait(cond_value_ptr, mutex, abstime, CLOCK_MONOTONIC);
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extern "C" int pthread_cond_timedwait_monotonic_np(pthread_cond_t* cond_interface,
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pthread_mutex_t* mutex,
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const timespec* abs_timeout) {
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return pthread_cond_timedwait_monotonic(cond_interface, mutex, abs_timeout);
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}
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extern "C" int pthread_cond_timedwait_relative_np(pthread_cond_t* cond, pthread_mutex_t* mutex, const timespec* reltime) {
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atomic_uint* cond_value_ptr = COND_TO_ATOMIC_POINTER(cond);
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return __pthread_cond_timedwait_relative(cond_value_ptr, mutex, reltime);
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extern "C" int pthread_cond_timedwait_relative_np(pthread_cond_t* cond_interface,
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pthread_mutex_t* mutex,
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const timespec* rel_timeout) {
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return __pthread_cond_timedwait_relative(__get_internal_cond(cond_interface), mutex, rel_timeout);
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}
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extern "C" int pthread_cond_timeout_np(pthread_cond_t* cond, pthread_mutex_t* mutex, unsigned ms) {
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extern "C" int pthread_cond_timeout_np(pthread_cond_t* cond_interface,
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pthread_mutex_t* mutex, unsigned ms) {
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timespec ts;
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timespec_from_ms(ts, ms);
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atomic_uint* cond_value_ptr = COND_TO_ATOMIC_POINTER(cond);
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return __pthread_cond_timedwait_relative(cond_value_ptr, mutex, &ts);
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return pthread_cond_timedwait_relative_np(cond_interface, mutex, &ts);
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}
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#endif // !defined(__LP64__)
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@ -73,13 +73,14 @@ enum {
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};
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typedef struct {
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unsigned int value;
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#ifdef __LP64__
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char __reserved[44];
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#if defined(__LP64__)
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char __private[48];
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#else
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char __private[4];
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#endif
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} pthread_cond_t;
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#define PTHREAD_COND_INITIALIZER {0 __RESERVED_INITIALIZER}
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#define PTHREAD_COND_INITIALIZER { { 0 } }
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typedef long pthread_mutexattr_t;
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typedef long pthread_condattr_t;
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@ -875,7 +875,7 @@ TEST(pthread, pthread_condattr_setclock) {
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}
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TEST(pthread, pthread_cond_broadcast__preserves_condattr_flags) {
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#if defined(__BIONIC__) // This tests a bionic implementation detail.
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#if defined(__BIONIC__)
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pthread_condattr_t attr;
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pthread_condattr_init(&attr);
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@ -888,16 +888,78 @@ TEST(pthread, pthread_cond_broadcast__preserves_condattr_flags) {
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ASSERT_EQ(0, pthread_cond_signal(&cond_var));
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ASSERT_EQ(0, pthread_cond_broadcast(&cond_var));
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attr = static_cast<pthread_condattr_t>(cond_var.value);
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attr = static_cast<pthread_condattr_t>(*reinterpret_cast<uint32_t*>(cond_var.__private));
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clockid_t clock;
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ASSERT_EQ(0, pthread_condattr_getclock(&attr, &clock));
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ASSERT_EQ(CLOCK_MONOTONIC, clock);
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int pshared;
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ASSERT_EQ(0, pthread_condattr_getpshared(&attr, &pshared));
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ASSERT_EQ(PTHREAD_PROCESS_SHARED, pshared);
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#else // __BIONIC__
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GTEST_LOG_(INFO) << "This test does nothing.\n";
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#endif // __BIONIC__
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#else // !defined(__BIONIC__)
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GTEST_LOG_(INFO) << "This tests a bionic implementation detail.\n";
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#endif // !defined(__BIONIC__)
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}
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class pthread_CondWakeupTest : public ::testing::Test {
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protected:
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pthread_mutex_t mutex;
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pthread_cond_t cond;
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enum Progress {
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INITIALIZED,
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WAITING,
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SIGNALED,
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FINISHED,
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};
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std::atomic<Progress> progress;
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pthread_t thread;
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protected:
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virtual void SetUp() {
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ASSERT_EQ(0, pthread_mutex_init(&mutex, NULL));
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ASSERT_EQ(0, pthread_cond_init(&cond, NULL));
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progress = INITIALIZED;
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ASSERT_EQ(0,
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pthread_create(&thread, NULL, reinterpret_cast<void* (*)(void*)>(WaitThreadFn), this));
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}
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virtual void TearDown() {
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ASSERT_EQ(0, pthread_join(thread, NULL));
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ASSERT_EQ(FINISHED, progress);
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ASSERT_EQ(0, pthread_cond_destroy(&cond));
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ASSERT_EQ(0, pthread_mutex_destroy(&mutex));
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}
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void SleepUntilProgress(Progress expected_progress) {
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while (progress != expected_progress) {
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usleep(5000);
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}
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usleep(5000);
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}
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private:
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static void WaitThreadFn(pthread_CondWakeupTest* test) {
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ASSERT_EQ(0, pthread_mutex_lock(&test->mutex));
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test->progress = WAITING;
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while (test->progress == WAITING) {
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ASSERT_EQ(0, pthread_cond_wait(&test->cond, &test->mutex));
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}
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ASSERT_EQ(SIGNALED, test->progress);
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test->progress = FINISHED;
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ASSERT_EQ(0, pthread_mutex_unlock(&test->mutex));
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}
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};
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TEST_F(pthread_CondWakeupTest, signal) {
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SleepUntilProgress(WAITING);
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progress = SIGNALED;
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pthread_cond_signal(&cond);
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}
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TEST_F(pthread_CondWakeupTest, broadcast) {
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SleepUntilProgress(WAITING);
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progress = SIGNALED;
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pthread_cond_broadcast(&cond);
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}
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TEST(pthread, pthread_mutex_timedlock) {
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