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Fix bug for recursive/errorcheck mutex on 32-bit devices.

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Bug: 19216648
Change-Id: I3b43b2d18d25b9bde352da1e35f9568133dec7cf
This commit is contained in:
Yabin Cui
2015-04-02 17:47:48 -07:00
parent 06b6e3c51d
commit f796985923
4 changed files with 76 additions and 19 deletions
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26
libc/bionic/pthread_mutex.cpp
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@@ -392,6 +392,30 @@ static inline __always_inline int __recursive_increment(pthread_mutex_internal_t
return 0;
}
static inline __always_inline int __recursive_or_errorcheck_mutex_wait(
pthread_mutex_internal_t* mutex,
uint16_t shared,
uint16_t old_state,
const timespec* rel_timeout) {
// __futex_wait always waits on a 32-bit value. But state is 16-bit. For a normal mutex, the owner_tid
// field in mutex is not used. On 64-bit devices, the __pad field in mutex is not used.
// But when a recursive or errorcheck mutex is used on 32-bit devices, we need to add the
// owner_tid value in the value argument for __futex_wait, otherwise we may always get EAGAIN error.
#if defined(__LP64__)
return __futex_wait_ex(&mutex->state, shared, old_state, rel_timeout);
#else
// This implementation works only when the layout of pthread_mutex_internal_t matches below expectation.
// And it is based on the assumption that Android is always in little-endian devices.
static_assert(offsetof(pthread_mutex_internal_t, state) == 0, "");
static_assert(offsetof(pthread_mutex_internal_t, owner_tid) == 2, "");
uint32_t owner_tid = atomic_load_explicit(&mutex->owner_tid, memory_order_relaxed);
return __futex_wait_ex(&mutex->state, shared, (owner_tid << 16) | old_state, rel_timeout);
#endif
}
static int __pthread_mutex_lock_with_timeout(pthread_mutex_internal_t* mutex,
const timespec* abs_timeout_or_null, clockid_t clock) {
uint16_t old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed);
@@ -469,7 +493,7 @@ static int __pthread_mutex_lock_with_timeout(pthread_mutex_internal_t* mutex,
return ETIMEDOUT;
}
}
if (__futex_wait_ex(&mutex->state, shared, old_state, rel_timeout) == -ETIMEDOUT) {
if (__recursive_or_errorcheck_mutex_wait(mutex, shared, old_state, rel_timeout) == -ETIMEDOUT) {
return ETIMEDOUT;
}
old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed);