[Qemu-devel] [PATCH 2/5] semaphore: implement fallback counting semaphores with mutex+condvar

[Paolo Bonzini <pbonzini@redhat.com>]

OpenBSD and Darwin do not have sem_timedwait.  Implement a fallback
for them.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 qemu-thread-posix.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 qemu-thread-posix.h |  6 +++++
 2 file modificati, 80 inserzioni(+)

diff --git a/qemu-thread-posix.c b/qemu-thread-posix.c
index 6a3d3a1..048db8f 100644
--- a/qemu-thread-posix.c
+++ b/qemu-thread-posix.c
@@ -122,36 +122,100 @@ void qemu_sem_init(QemuSemaphore *sem, int init)
 {
     int rc;
 
+#if defined(__OpenBSD__) || defined(__APPLE__) || defined(__NetBSD__)
+    rc = pthread_mutex_init(&sem->lock, NULL);
+    if (rc != 0) {
+        error_exit(rc, __func__);
+    }
+    rc = pthread_cond_init(&sem->cond, NULL);
+    if (rc != 0) {
+        error_exit(rc, __func__);
+    }
+    if (init < 0) {
+        error_exit(EINVAL, __func__);
+    }
+    sem->count = init;
+#else
     rc = sem_init(&sem->sem, 0, init);
     if (rc < 0) {
         error_exit(errno, __func__);
     }
+#endif
 }
 
 void qemu_sem_destroy(QemuSemaphore *sem)
 {
     int rc;
 
+#if defined(__OpenBSD__) || defined(__APPLE__) || defined(__NetBSD__)
+    rc = pthread_cond_destroy(&sem->cond);
+    if (rc < 0) {
+        error_exit(rc, __func__);
+    }
+    rc = pthread_mutex_destroy(&sem->lock);
+    if (rc < 0) {
+        error_exit(rc, __func__);
+    }
+#else
     rc = sem_destroy(&sem->sem);
     if (rc < 0) {
         error_exit(errno, __func__);
     }
+#endif
 }
 
 void qemu_sem_post(QemuSemaphore *sem)
 {
     int rc;
 
+#if defined(__OpenBSD__) || defined(__APPLE__) || defined(__NetBSD__)
+    pthread_mutex_lock(&sem->lock);
+    if (sem->count == INT_MAX) {
+        rc = EINVAL;
+    } else if (sem->count++ < 0) {
+        rc = pthread_cond_signal(&sem->cond);
+    } else {
+        rc = 0;
+    }
+    pthread_mutex_unlock(&sem->lock);
+    if (rc != 0) {
+        error_exit(rc, __func__);
+    }
+#else
     rc = sem_post(&sem->sem);
     if (rc < 0) {
         error_exit(errno, __func__);
     }
+#endif
 }
 
 int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
 {
     int rc;
 
+#if defined(__OpenBSD__) || defined(__APPLE__) || defined(__NetBSD__)
+    struct timespec ts;
+    clock_gettime(CLOCK_REALTIME, &ts);
+    if (ms) {
+        int nsec = ts.tv_nsec + (ms % 1000) * 1000000;
+        ts.tv_sec += ms / 1000 + nsec / 1000000000;
+        ts.tv_nsec = nsec % 1000000000;
+    }
+
+    pthread_mutex_lock(&sem->lock);
+    --sem->count;
+    while (sem->count < 0) {
+        rc = pthread_cond_timedwait(&sem->cond, &sem->lock, &ts);
+        if (rc == ETIMEDOUT) {
+            break;
+        }
+        if (rc != 0) {
+            error_exit(rc, __func__);
+        }
+    }
+    pthread_mutex_unlock(&sem->lock);
+    return (rc == ETIMEDOUT ? -1 : 0);
+#else
     if (ms <= 0) {
         /* This is cheaper than sem_timedwait.  */
         do {
@@ -181,10 +245,19 @@ int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
         error_exit(errno, __func__);
     }
     return 0;
+#endif
 }
 
 void qemu_sem_wait(QemuSemaphore *sem)
 {
+#if defined(__OpenBSD__) || defined(__APPLE__) || defined(__NetBSD__)
+    pthread_mutex_lock(&sem->lock);
+    --sem->count;
+    while (sem->count < 0) {
+        pthread_cond_wait(&sem->cond, &sem->lock);
+    }
+    pthread_mutex_unlock(&sem->lock);
+#else
     int rc;
 
     do {
@@ -193,6 +266,7 @@ void qemu_sem_wait(QemuSemaphore *sem)
     if (rc < 0) {
         error_exit(errno, __func__);
     }
+#endif
 }
 
 void qemu_thread_create(QemuThread *thread,
diff --git a/qemu-thread-posix.h b/qemu-thread-posix.h
index 2542c15..1c098c2 100644
--- a/qemu-thread-posix.h
+++ b/qemu-thread-posix.h
@@ -12,7 +12,13 @@ struct QemuCond {
 };
 
 struct QemuSemaphore {
+#if defined(__OpenBSD__) || defined(__APPLE__) || defined(__NetBSD__)
+    pthread_mutex_t lock;
+    pthread_cond_t cond;
+    int count;
+#else
     sem_t sem;
+#endif
 };
 
 struct QemuThread {
-- 
1.7.12.1