Support priority inheritance mutex in 64bit programs.
Bug: http://b/29177606
Test: run bionic-unit-tests on walleye.
Test: run bionic-unit-tests-glibc on host.
Change-Id: Iac349284aa73515f384e7509445f87434757f59e
diff --git a/libc/bionic/pthread_mutex.cpp b/libc/bionic/pthread_mutex.cpp
index 14e0ab0..ed90639 100644
--- a/libc/bionic/pthread_mutex.cpp
+++ b/libc/bionic/pthread_mutex.cpp
@@ -49,9 +49,13 @@
* bits: name description
* 0-3 type type of mutex
* 4 shared process-shared flag
+ * 5 protocol whether it is a priority inherit mutex.
*/
#define MUTEXATTR_TYPE_MASK 0x000f
#define MUTEXATTR_SHARED_MASK 0x0010
+#define MUTEXATTR_PROTOCOL_MASK 0x0020
+
+#define MUTEXATTR_PROTOCOL_SHIFT 5
int pthread_mutexattr_init(pthread_mutexattr_t *attr)
{
@@ -113,17 +117,119 @@
return 0;
}
-/* a mutex contains a state value and a owner_tid.
- * The value is implemented as a 16-bit integer holding the following fields:
- *
- * bits: name description
- * 15-14 type mutex type
- * 13 shared process-shared flag
- * 12-2 counter counter of recursive mutexes
- * 1-0 state lock state (0, 1 or 2)
- *
- * The owner_tid is used only in recursive and errorcheck mutex to hold the mutex owner thread tid.
- */
+int pthread_mutexattr_setprotocol(pthread_mutexattr_t* attr, int protocol) {
+ if (protocol != PTHREAD_PRIO_NONE && protocol != PTHREAD_PRIO_INHERIT) {
+ return EINVAL;
+ }
+ *attr = (*attr & ~MUTEXATTR_PROTOCOL_MASK) | (protocol << MUTEXATTR_PROTOCOL_SHIFT);
+ return 0;
+}
+
+int pthread_mutexattr_getprotocol(const pthread_mutexattr_t* attr, int* protocol) {
+ *protocol = (*attr & MUTEXATTR_PROTOCOL_MASK) >> MUTEXATTR_PROTOCOL_SHIFT;
+ return 0;
+}
+
+#if defined(__LP64__)
+
+// Priority Inheritance mutex implementation
+struct PIMutex {
+ // mutex type, can be 0 (normal), 1 (recursive), 2 (errorcheck), constant during lifetime
+ uint8_t type;
+ // process-shared flag, constant during lifetime
+ bool shared;
+ // <number of times a thread holding a recursive PI mutex> - 1
+ uint16_t counter;
+ // owner_tid is read/written by both userspace code and kernel code. It includes three fields:
+ // FUTEX_WAITERS, FUTEX_OWNER_DIED and FUTEX_TID_MASK.
+ atomic_int owner_tid;
+};
+
+static inline __always_inline int PIMutexTryLock(PIMutex& mutex) {
+ pid_t tid = __get_thread()->tid;
+ // Handle common case first.
+ int old_owner = 0;
+ if (__predict_true(atomic_compare_exchange_strong_explicit(&mutex.owner_tid,
+ &old_owner, tid,
+ memory_order_acquire,
+ memory_order_relaxed))) {
+ return 0;
+ }
+ if (tid == (old_owner & FUTEX_TID_MASK)) {
+ // We already own this mutex.
+ if (mutex.type == PTHREAD_MUTEX_NORMAL) {
+ return EBUSY;
+ }
+ if (mutex.type == PTHREAD_MUTEX_ERRORCHECK) {
+ return EDEADLK;
+ }
+ if (mutex.counter == 0xffff) {
+ return EAGAIN;
+ }
+ mutex.counter++;
+ return 0;
+ }
+ return EBUSY;
+}
+
+static int PIMutexTimedLock(PIMutex& mutex, const timespec* abs_timeout) {
+ int ret = PIMutexTryLock(mutex);
+ if (__predict_true(ret == 0)) {
+ return 0;
+ }
+ if (ret == EBUSY) {
+ ret = -__futex_pi_lock_ex(&mutex.owner_tid, mutex.shared, true, abs_timeout);
+ }
+ return ret;
+}
+
+static int PIMutexUnlock(PIMutex& mutex) {
+ pid_t tid = __get_thread()->tid;
+ int old_owner = tid;
+ // Handle common case first.
+ if (__predict_true(mutex.type == PTHREAD_MUTEX_NORMAL)) {
+ if (__predict_true(atomic_compare_exchange_strong_explicit(&mutex.owner_tid,
+ &old_owner, 0,
+ memory_order_release,
+ memory_order_relaxed))) {
+ return 0;
+ }
+ }
+
+ if (tid != (old_owner & FUTEX_TID_MASK)) {
+ // The mutex can only be unlocked by the thread who owns it.
+ return EPERM;
+ }
+ if (mutex.type == PTHREAD_MUTEX_RECURSIVE) {
+ if (mutex.counter != 0u) {
+ --mutex.counter;
+ return 0;
+ }
+ }
+ if (old_owner == tid) {
+ // No thread is waiting.
+ if (__predict_true(atomic_compare_exchange_strong_explicit(&mutex.owner_tid,
+ &old_owner, 0,
+ memory_order_release,
+ memory_order_relaxed))) {
+ return 0;
+ }
+ }
+ return -__futex_pi_unlock(&mutex.owner_tid, mutex.shared);
+}
+
+static int PIMutexDestroy(PIMutex& mutex) {
+ // The mutex should be in unlocked state (owner_tid == 0) when destroyed.
+ // Store 0xffffffff to make the mutex unusable.
+ int old_owner = 0;
+ if (atomic_compare_exchange_strong_explicit(&mutex.owner_tid, &old_owner, 0xffffffff,
+ memory_order_relaxed, memory_order_relaxed)) {
+ return 0;
+ }
+ return EBUSY;
+}
+#endif // defined(__LP64__)
+
/* Convenience macro, creates a mask of 'bits' bits that starts from
* the 'shift'-th least significant bit in a 32-bit word.
@@ -139,7 +245,6 @@
/* And this one does the opposite, i.e. extract a field's value from a bit pattern */
#define FIELD_FROM_BITS(val,shift,bits) (((val) >> (shift)) & ((1 << (bits))-1))
-
/* Convenience macros.
*
* These are used to form or modify the bit pattern of a given mutex value
@@ -214,13 +319,47 @@
#define MUTEX_TYPE_BITS_NORMAL MUTEX_TYPE_TO_BITS(PTHREAD_MUTEX_NORMAL)
#define MUTEX_TYPE_BITS_RECURSIVE MUTEX_TYPE_TO_BITS(PTHREAD_MUTEX_RECURSIVE)
#define MUTEX_TYPE_BITS_ERRORCHECK MUTEX_TYPE_TO_BITS(PTHREAD_MUTEX_ERRORCHECK)
+// Use a special mutex type to mark priority inheritance mutexes.
+#define MUTEX_TYPE_BITS_WITH_PI MUTEX_TYPE_TO_BITS(3)
+// For a PI mutex, it includes below fields:
+// Atomic(uint16_t) state;
+// PIMutex pi_mutex;
+//
+// state holds the following fields:
+//
+// bits: name description
+// 15-14 type mutex type, should be 3
+//
+// pi_mutex holds the state of a PI mutex.
+//
+// For a Non-PI mutex, it includes below fields:
+// Atomic(uint16_t) state;
+// atomic_int owner_tid; // Atomic(uint16_t) in 32-bit programs
+//
+// state holds the following fields:
+//
+// bits: name description
+// 15-14 type mutex type, can be 0 (normal), 1 (recursive), 2 (errorcheck)
+// 13 shared process-shared flag
+// 12-2 counter <number of times a thread holding a recursive Non-PI mutex> - 1
+// 1-0 state lock state (0, 1 or 2)
+//
+// bits 15-13 are constant during the lifetime of the mutex.
+//
+// owner_tid is used only in recursive and errorcheck Non-PI mutexes to hold the mutex owner
+// thread id.
+//
+// PI mutexes and Non-PI mutexes are distinguished by checking type field in state.
struct pthread_mutex_internal_t {
_Atomic(uint16_t) state;
#if defined(__LP64__)
uint16_t __pad;
- atomic_int owner_tid;
- char __reserved[32];
+ union {
+ atomic_int owner_tid;
+ PIMutex pi_mutex;
+ };
+ char __reserved[28];
#else
_Atomic(uint16_t) owner_tid;
#endif
@@ -267,13 +406,26 @@
return EINVAL;
}
- atomic_init(&mutex->state, state);
- atomic_init(&mutex->owner_tid, 0);
+ if (((*attr & MUTEXATTR_PROTOCOL_MASK) >> MUTEXATTR_PROTOCOL_SHIFT) == PTHREAD_PRIO_INHERIT) {
+#if defined(__LP64__)
+ atomic_init(&mutex->state, MUTEX_TYPE_BITS_WITH_PI);
+ mutex->pi_mutex.type = *attr & MUTEXATTR_TYPE_MASK;
+ mutex->pi_mutex.shared = (*attr & MUTEXATTR_SHARED_MASK) != 0;
+#else
+ return EINVAL;
+#endif
+ } else {
+ atomic_init(&mutex->state, state);
+ atomic_init(&mutex->owner_tid, 0);
+ }
return 0;
}
-static inline __always_inline int __pthread_normal_mutex_trylock(pthread_mutex_internal_t* mutex,
- uint16_t shared) {
+// namespace for Non-PI mutex routines.
+namespace NonPI {
+
+static inline __always_inline int NormalMutexTryLock(pthread_mutex_internal_t* mutex,
+ uint16_t shared) {
const uint16_t unlocked = shared | MUTEX_STATE_BITS_UNLOCKED;
const uint16_t locked_uncontended = shared | MUTEX_STATE_BITS_LOCKED_UNCONTENDED;
@@ -286,7 +438,7 @@
}
/*
- * Lock a mutex of type NORMAL.
+ * Lock a normal Non-PI mutex.
*
* As noted above, there are three states:
* 0 (unlocked, no contention)
@@ -297,11 +449,11 @@
* "type" value is zero, so the only bits that will be set are the ones in
* the lock state field.
*/
-static inline __always_inline int __pthread_normal_mutex_lock(pthread_mutex_internal_t* mutex,
- uint16_t shared,
- bool use_realtime_clock,
- const timespec* abs_timeout_or_null) {
- if (__predict_true(__pthread_normal_mutex_trylock(mutex, shared) == 0)) {
+static inline __always_inline int NormalMutexLock(pthread_mutex_internal_t* mutex,
+ uint16_t shared,
+ bool use_realtime_clock,
+ const timespec* abs_timeout_or_null) {
+ if (__predict_true(NormalMutexTryLock(mutex, shared) == 0)) {
return 0;
}
int result = check_timespec(abs_timeout_or_null, true);
@@ -333,11 +485,11 @@
}
/*
- * Release a normal mutex. The caller is responsible for determining
+ * Release a normal Non-PI mutex. The caller is responsible for determining
* that we are in fact the owner of this lock.
*/
-static inline __always_inline void __pthread_normal_mutex_unlock(pthread_mutex_internal_t* mutex,
- uint16_t shared) {
+static inline __always_inline void NormalMutexUnlock(pthread_mutex_internal_t* mutex,
+ uint16_t shared) {
const uint16_t unlocked = shared | MUTEX_STATE_BITS_UNLOCKED;
const uint16_t locked_contended = shared | MUTEX_STATE_BITS_LOCKED_CONTENDED;
@@ -370,14 +522,14 @@
}
}
-/* This common inlined function is used to increment the counter of a recursive mutex.
+/* This common inlined function is used to increment the counter of a recursive Non-PI mutex.
*
* If the counter overflows, it will return EAGAIN.
* Otherwise, it atomically increments the counter and returns 0.
*
*/
-static inline __always_inline int __recursive_increment(pthread_mutex_internal_t* mutex,
- uint16_t old_state) {
+static inline __always_inline int RecursiveIncrement(pthread_mutex_internal_t* mutex,
+ uint16_t old_state) {
// Detect recursive lock overflow and return EAGAIN.
// This is safe because only the owner thread can modify the
// counter bits in the mutex value.
@@ -387,17 +539,17 @@
// Other threads are able to change the lower bits (e.g. promoting it to "contended"),
// but the mutex counter will not overflow. So we use atomic_fetch_add operation here.
- // The mutex is still locked by current thread, so we don't need a release fence.
+ // The mutex is already locked by current thread, so we don't need an acquire fence.
atomic_fetch_add_explicit(&mutex->state, MUTEX_COUNTER_BITS_ONE, memory_order_relaxed);
return 0;
}
-static inline __always_inline int __recursive_or_errorcheck_mutex_wait(
- pthread_mutex_internal_t* mutex,
- uint16_t shared,
- uint16_t old_state,
- bool use_realtime_clock,
- const timespec* abs_timeout) {
+// Wait on a recursive or errorcheck Non-PI mutex.
+static inline __always_inline int RecursiveOrErrorcheckMutexWait(pthread_mutex_internal_t* mutex,
+ uint16_t shared,
+ uint16_t old_state,
+ bool use_realtime_clock,
+ const timespec* abs_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
@@ -418,16 +570,16 @@
#endif
}
-static int __pthread_mutex_lock_with_timeout(pthread_mutex_internal_t* mutex,
- bool use_realtime_clock,
- const timespec* abs_timeout_or_null) {
+// Lock a Non-PI mutex.
+static int MutexLockWithTimeout(pthread_mutex_internal_t* mutex, bool use_realtime_clock,
+ const timespec* abs_timeout_or_null) {
uint16_t old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed);
uint16_t mtype = (old_state & MUTEX_TYPE_MASK);
uint16_t shared = (old_state & MUTEX_SHARED_MASK);
// Handle common case first.
if ( __predict_true(mtype == MUTEX_TYPE_BITS_NORMAL) ) {
- return __pthread_normal_mutex_lock(mutex, shared, use_realtime_clock, abs_timeout_or_null);
+ return NormalMutexLock(mutex, shared, use_realtime_clock, abs_timeout_or_null);
}
// Do we already own this recursive or error-check mutex?
@@ -436,7 +588,7 @@
if (mtype == MUTEX_TYPE_BITS_ERRORCHECK) {
return EDEADLK;
}
- return __recursive_increment(mutex, old_state);
+ return RecursiveIncrement(mutex, old_state);
}
const uint16_t unlocked = mtype | shared | MUTEX_STATE_BITS_UNLOCKED;
@@ -492,14 +644,16 @@
return result;
}
// We are in locked_contended state, sleep until someone wakes us up.
- if (__recursive_or_errorcheck_mutex_wait(mutex, shared, old_state, use_realtime_clock,
- abs_timeout_or_null) == -ETIMEDOUT) {
+ if (RecursiveOrErrorcheckMutexWait(mutex, shared, old_state, use_realtime_clock,
+ abs_timeout_or_null) == -ETIMEDOUT) {
return ETIMEDOUT;
}
old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed);
}
}
+} // namespace NonPI
+
int pthread_mutex_lock(pthread_mutex_t* mutex_interface) {
#if !defined(__LP64__)
// Some apps depend on being able to pass NULL as a mutex and get EINVAL
@@ -517,11 +671,16 @@
uint16_t shared = (old_state & MUTEX_SHARED_MASK);
// Avoid slowing down fast path of normal mutex lock operation.
if (__predict_true(mtype == MUTEX_TYPE_BITS_NORMAL)) {
- if (__predict_true(__pthread_normal_mutex_trylock(mutex, shared) == 0)) {
+ if (__predict_true(NonPI::NormalMutexTryLock(mutex, shared) == 0)) {
return 0;
}
}
- return __pthread_mutex_lock_with_timeout(mutex, false, nullptr);
+#if defined(__LP64__)
+ if (mtype == MUTEX_TYPE_BITS_WITH_PI) {
+ return PIMutexTimedLock(mutex->pi_mutex, nullptr);
+ }
+#endif
+ return NonPI::MutexLockWithTimeout(mutex, false, nullptr);
}
int pthread_mutex_unlock(pthread_mutex_t* mutex_interface) {
@@ -542,9 +701,14 @@
// Handle common case first.
if (__predict_true(mtype == MUTEX_TYPE_BITS_NORMAL)) {
- __pthread_normal_mutex_unlock(mutex, shared);
+ NonPI::NormalMutexUnlock(mutex, shared);
return 0;
}
+#if defined(__LP64__)
+ if (mtype == MUTEX_TYPE_BITS_WITH_PI) {
+ return PIMutexUnlock(mutex->pi_mutex);
+ }
+#endif
// Do we already own this recursive or error-check mutex?
pid_t tid = __get_thread()->tid;
@@ -582,15 +746,17 @@
uint16_t old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed);
uint16_t mtype = (old_state & MUTEX_TYPE_MASK);
- uint16_t shared = (old_state & MUTEX_SHARED_MASK);
-
- const uint16_t unlocked = mtype | shared | MUTEX_STATE_BITS_UNLOCKED;
- const uint16_t locked_uncontended = mtype | shared | MUTEX_STATE_BITS_LOCKED_UNCONTENDED;
// Handle common case first.
if (__predict_true(mtype == MUTEX_TYPE_BITS_NORMAL)) {
- return __pthread_normal_mutex_trylock(mutex, shared);
+ uint16_t shared = (old_state & MUTEX_SHARED_MASK);
+ return NonPI::NormalMutexTryLock(mutex, shared);
}
+#if defined(__LP64__)
+ if (mtype == MUTEX_TYPE_BITS_WITH_PI) {
+ return PIMutexTryLock(mutex->pi_mutex);
+ }
+#endif
// Do we already own this recursive or error-check mutex?
pid_t tid = __get_thread()->tid;
@@ -598,9 +764,13 @@
if (mtype == MUTEX_TYPE_BITS_ERRORCHECK) {
return EBUSY;
}
- return __recursive_increment(mutex, old_state);
+ return NonPI::RecursiveIncrement(mutex, old_state);
}
+ uint16_t shared = (old_state & MUTEX_SHARED_MASK);
+ const uint16_t unlocked = mtype | shared | MUTEX_STATE_BITS_UNLOCKED;
+ const uint16_t locked_uncontended = mtype | shared | MUTEX_STATE_BITS_LOCKED_UNCONTENDED;
+
// Same as pthread_mutex_lock, except that we don't want to wait, and
// the only operation that can succeed is a single compare_exchange to acquire the
// lock if it is released / not owned by anyone. No need for a complex loop.
@@ -623,8 +793,8 @@
timespec_from_ms(ts, ms);
timespec abs_timeout;
absolute_timespec_from_timespec(abs_timeout, ts, CLOCK_MONOTONIC);
- int error = __pthread_mutex_lock_with_timeout(__get_internal_mutex(mutex_interface),
- false, &abs_timeout);
+ int error = NonPI::MutexLockWithTimeout(__get_internal_mutex(mutex_interface), false,
+ &abs_timeout);
if (error == ETIMEDOUT) {
error = EBUSY;
}
@@ -633,13 +803,33 @@
#endif
int pthread_mutex_timedlock(pthread_mutex_t* mutex_interface, const timespec* abs_timeout) {
- return __pthread_mutex_lock_with_timeout(__get_internal_mutex(mutex_interface),
- true, abs_timeout);
+ pthread_mutex_internal_t* mutex = __get_internal_mutex(mutex_interface);
+ uint16_t old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed);
+ uint16_t mtype = (old_state & MUTEX_TYPE_MASK);
+ // Handle common case first.
+ if (__predict_true(mtype == MUTEX_TYPE_BITS_NORMAL)) {
+ uint16_t shared = (old_state & MUTEX_SHARED_MASK);
+ if (__predict_true(NonPI::NormalMutexTryLock(mutex, shared) == 0)) {
+ return 0;
+ }
+ }
+#if defined(__LP64__)
+ if (mtype == MUTEX_TYPE_BITS_WITH_PI) {
+ return PIMutexTimedLock(mutex->pi_mutex, abs_timeout);
+ }
+#endif
+ return NonPI::MutexLockWithTimeout(mutex, true, abs_timeout);
}
int pthread_mutex_destroy(pthread_mutex_t* mutex_interface) {
pthread_mutex_internal_t* mutex = __get_internal_mutex(mutex_interface);
uint16_t old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed);
+#if defined(__LP64__)
+ uint16_t mtype = (old_state & MUTEX_TYPE_MASK);
+ if (mtype == MUTEX_TYPE_BITS_WITH_PI) {
+ return PIMutexDestroy(mutex->pi_mutex);
+ }
+#endif
// Store 0xffff to make the mutex unusable. Although POSIX standard says it is undefined
// behavior to destroy a locked mutex, we prefer not to change mutex->state in that situation.
if (MUTEX_STATE_BITS_IS_UNLOCKED(old_state) &&