Add semaphore tests, fix sem_destroy.
Bug: https://code.google.com/p/android/issues/detail?id=76088
Change-Id: I4a0561b23e90312384d40a1c804ca64ee98f4066
diff --git a/libc/bionic/semaphore.cpp b/libc/bionic/semaphore.cpp
new file mode 100644
index 0000000..c23eb75
--- /dev/null
+++ b/libc/bionic/semaphore.cpp
@@ -0,0 +1,322 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <semaphore.h>
+#include <errno.h>
+#include <limits.h>
+#include <sys/time.h>
+#include <time.h>
+
+#include "private/bionic_atomic_inline.h"
+#include "private/bionic_constants.h"
+#include "private/bionic_futex.h"
+#include "private/bionic_time_conversions.h"
+
+// In this implementation, a semaphore contains a
+// 31-bit signed value and a 1-bit 'shared' flag
+// (for process-sharing purpose).
+//
+// We use the value -1 to indicate contention on the
+// semaphore, 0 or more to indicate uncontended state,
+// any value lower than -2 is invalid at runtime.
+//
+// State diagram:
+//
+// post(1) ==> 2
+// post(0) ==> 1
+// post(-1) ==> 1, then wake all waiters
+//
+// wait(2) ==> 1
+// wait(1) ==> 0
+// wait(0) ==> -1 then wait for a wake up + loop
+// wait(-1) ==> -1 then wait for a wake up + loop
+
+// Use the upper 31-bits for the counter, and the lower one
+// for the shared flag.
+#define SEMCOUNT_SHARED_MASK 0x00000001
+#define SEMCOUNT_VALUE_MASK 0xfffffffe
+#define SEMCOUNT_VALUE_SHIFT 1
+
+// Convert a value into the corresponding sem->count bit pattern.
+#define SEMCOUNT_FROM_VALUE(val) (((val) << SEMCOUNT_VALUE_SHIFT) & SEMCOUNT_VALUE_MASK)
+
+// Convert a sem->count bit pattern into the corresponding signed value.
+static inline int SEMCOUNT_TO_VALUE(uint32_t sval) {
+ return (static_cast<int>(sval) >> SEMCOUNT_VALUE_SHIFT);
+}
+
+// The value +1 as a sem->count bit-pattern.
+#define SEMCOUNT_ONE SEMCOUNT_FROM_VALUE(1)
+
+// The value -1 as a sem->count bit-pattern.
+#define SEMCOUNT_MINUS_ONE SEMCOUNT_FROM_VALUE(-1)
+
+#define SEMCOUNT_DECREMENT(sval) (((sval) - (1U << SEMCOUNT_VALUE_SHIFT)) & SEMCOUNT_VALUE_MASK)
+#define SEMCOUNT_INCREMENT(sval) (((sval) + (1U << SEMCOUNT_VALUE_SHIFT)) & SEMCOUNT_VALUE_MASK)
+
+// Return the shared bitflag from a semaphore.
+static inline uint32_t SEM_GET_SHARED(sem_t* sem) {
+ return (sem->count & SEMCOUNT_SHARED_MASK);
+}
+
+
+int sem_init(sem_t* sem, int pshared, unsigned int value) {
+ if (sem == NULL) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ // Ensure that 'value' can be stored in the semaphore.
+ if (value > SEM_VALUE_MAX) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ sem->count = SEMCOUNT_FROM_VALUE(value);
+ if (pshared != 0) {
+ sem->count |= SEMCOUNT_SHARED_MASK;
+ }
+ return 0;
+}
+
+int sem_destroy(sem_t* sem) {
+ if (sem == NULL) {
+ errno = EINVAL;
+ return -1;
+ }
+ return 0;
+}
+
+sem_t* sem_open(const char*, int, ...) {
+ errno = ENOSYS;
+ return SEM_FAILED;
+}
+
+int sem_close(sem_t*) {
+ errno = ENOSYS;
+ return -1;
+}
+
+int sem_unlink(const char*) {
+ errno = ENOSYS;
+ return -1;
+}
+
+// Decrement a semaphore's value atomically,
+// and return the old one. As a special case,
+// this returns immediately if the value is
+// negative (i.e. -1)
+static int __sem_dec(volatile uint32_t* sem) {
+ volatile int32_t* ptr = reinterpret_cast<volatile int32_t*>(sem);
+ uint32_t shared = (*sem & SEMCOUNT_SHARED_MASK);
+ uint32_t old_value, new_value;
+ int ret;
+
+ do {
+ old_value = (*sem & SEMCOUNT_VALUE_MASK);
+ ret = SEMCOUNT_TO_VALUE(old_value);
+ if (ret < 0) {
+ break;
+ }
+
+ new_value = SEMCOUNT_DECREMENT(old_value);
+ } while (__bionic_cmpxchg((old_value|shared), (new_value|shared), ptr) != 0);
+
+ return ret;
+}
+
+// Same as __sem_dec, but will not touch anything if the
+// value is already negative *or* 0. Returns the old value.
+static int __sem_trydec(volatile uint32_t* sem) {
+ volatile int32_t* ptr = reinterpret_cast<volatile int32_t*>(sem);
+ uint32_t shared = (*sem & SEMCOUNT_SHARED_MASK);
+ uint32_t old_value, new_value;
+ int ret;
+
+ do {
+ old_value = (*sem & SEMCOUNT_VALUE_MASK);
+ ret = SEMCOUNT_TO_VALUE(old_value);
+ if (ret <= 0) {
+ break;
+ }
+
+ new_value = SEMCOUNT_DECREMENT(old_value);
+ } while (__bionic_cmpxchg((old_value|shared), (new_value|shared), ptr) != 0);
+
+ return ret;
+}
+
+
+// "Increment" the value of a semaphore atomically and
+// return its old value. Note that this implements
+// the special case of "incrementing" any negative
+// value to +1 directly.
+//
+// NOTE: The value will _not_ wrap above SEM_VALUE_MAX
+static int __sem_inc(volatile uint32_t* sem) {
+ volatile int32_t* ptr = reinterpret_cast<volatile int32_t*>(sem);
+ uint32_t shared = (*sem & SEMCOUNT_SHARED_MASK);
+ uint32_t old_value, new_value;
+ int ret;
+
+ do {
+ old_value = (*sem & SEMCOUNT_VALUE_MASK);
+ ret = SEMCOUNT_TO_VALUE(old_value);
+
+ // Can't go higher than SEM_VALUE_MAX.
+ if (ret == SEM_VALUE_MAX) {
+ break;
+ }
+
+ // If the counter is negative, go directly to +1, otherwise just increment.
+ if (ret < 0) {
+ new_value = SEMCOUNT_ONE;
+ } else {
+ new_value = SEMCOUNT_INCREMENT(old_value);
+ }
+ } while (__bionic_cmpxchg((old_value|shared), (new_value|shared), ptr) != 0);
+
+ return ret;
+}
+
+int sem_wait(sem_t* sem) {
+ if (sem == NULL) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ uint32_t shared = SEM_GET_SHARED(sem);
+
+ while (true) {
+ if (__sem_dec(&sem->count) > 0) {
+ ANDROID_MEMBAR_FULL();
+ return 0;
+ }
+
+ __futex_wait_ex(&sem->count, shared, shared|SEMCOUNT_MINUS_ONE, NULL);
+ }
+}
+
+int sem_timedwait(sem_t* sem, const timespec* abs_timeout) {
+ if (sem == NULL) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ // POSIX says we need to try to decrement the semaphore
+ // before checking the timeout value. Note that if the
+ // value is currently 0, __sem_trydec() does nothing.
+ if (__sem_trydec(&sem->count) > 0) {
+ ANDROID_MEMBAR_FULL();
+ return 0;
+ }
+
+ // Check it as per POSIX.
+ if (abs_timeout == NULL || abs_timeout->tv_sec < 0 || abs_timeout->tv_nsec < 0 || abs_timeout->tv_nsec >= NS_PER_S) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ uint32_t shared = SEM_GET_SHARED(sem);
+
+ while (true) {
+ // POSIX mandates CLOCK_REALTIME here.
+ timespec ts;
+ if (!timespec_from_absolute_timespec(ts, *abs_timeout, CLOCK_REALTIME)) {
+ errno = ETIMEDOUT;
+ return -1;
+ }
+
+ // Try to grab the semaphore. If the value was 0, this will also change it to -1.
+ if (__sem_dec(&sem->count) > 0) {
+ ANDROID_MEMBAR_FULL();
+ break;
+ }
+
+ // Contention detected. Wait for a wakeup event.
+ int ret = __futex_wait_ex(&sem->count, shared, shared|SEMCOUNT_MINUS_ONE, &ts);
+
+ // Return in case of timeout or interrupt.
+ if (ret == -ETIMEDOUT || ret == -EINTR) {
+ errno = -ret;
+ return -1;
+ }
+ }
+ return 0;
+}
+
+int sem_post(sem_t* sem) {
+ if (sem == NULL) {
+ return EINVAL;
+ }
+
+ uint32_t shared = SEM_GET_SHARED(sem);
+
+ ANDROID_MEMBAR_FULL();
+ int old_value = __sem_inc(&sem->count);
+ if (old_value < 0) {
+ // Contention on the semaphore. Wake up all waiters.
+ __futex_wake_ex(&sem->count, shared, INT_MAX);
+ } else if (old_value == SEM_VALUE_MAX) {
+ // Overflow detected.
+ errno = EOVERFLOW;
+ return -1;
+ }
+
+ return 0;
+}
+
+int sem_trywait(sem_t* sem) {
+ if (sem == NULL) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ if (__sem_trydec(&sem->count) > 0) {
+ ANDROID_MEMBAR_FULL();
+ return 0;
+ } else {
+ errno = EAGAIN;
+ return -1;
+ }
+}
+
+int sem_getvalue(sem_t* sem, int* sval) {
+ if (sem == NULL || sval == NULL) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ int val = SEMCOUNT_TO_VALUE(sem->count);
+ if (val < 0) {
+ val = 0;
+ }
+
+ *sval = val;
+ return 0;
+}