qemu-thread: add QemuSemaphore

The new thread pool will use semaphores instead of condition
variables, because QemuCond does not have qemu_cond_timedwait.
(I also like it more this way).

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

qemu-thread-posix.c

@@ -17,6 +17,9 @@
 #include <signal.h>
 #include <stdint.h>
 #include <string.h>
+#include <limits.h>
+#include <unistd.h>
+#include <sys/time.h>
 #include "qemu-thread.h"
 
 static void error_exit(int err, const char *msg)
@@ -115,6 +118,83 @@ void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex)
         error_exit(err, __func__);
 }
 
+void qemu_sem_init(QemuSemaphore *sem, int init)
+{
+    int rc;
+
+    rc = sem_init(&sem->sem, 0, init);
+    if (rc < 0) {
+        error_exit(errno, __func__);
+    }
+}
+
+void qemu_sem_destroy(QemuSemaphore *sem)
+{
+    int rc;
+
+    rc = sem_destroy(&sem->sem);
+    if (rc < 0) {
+        error_exit(errno, __func__);
+    }
+}
+
+void qemu_sem_post(QemuSemaphore *sem)
+{
+    int rc;
+
+    rc = sem_post(&sem->sem);
+    if (rc < 0) {
+        error_exit(errno, __func__);
+    }
+}
+
+int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
+{
+    int rc;
+
+    if (ms <= 0) {
+        /* This is cheaper than sem_timedwait.  */
+        do {
+            rc = sem_trywait(&sem->sem);
+        } while (rc == -1 && errno == EINTR);
+        if (rc == -1 && errno == EAGAIN) {
+            return -1;
+        }
+    } else {
+        struct timeval tv;
+        struct timespec ts;
+        gettimeofday(&tv, NULL);
+        ts.tv_nsec = tv.tv_usec * 1000 + (ms % 1000) * 1000000;
+        ts.tv_sec = tv.tv_sec + ms / 1000;
+        if (ts.tv_nsec >= 1000000000) {
+            ts.tv_sec++;
+            ts.tv_nsec -= 1000000000;
+        }
+        do {
+            rc = sem_timedwait(&sem->sem, &ts);
+        } while (rc == -1 && errno == EINTR);
+        if (rc == -1 && errno == ETIMEDOUT) {
+            return -1;
+        }
+    }
+    if (rc < 0) {
+        error_exit(errno, __func__);
+    }
+    return 0;
+}
+
+void qemu_sem_wait(QemuSemaphore *sem)
+{
+    int rc;
+
+    do {
+        rc = sem_wait(&sem->sem);
+    } while (rc == -1 && errno == EINTR);
+    if (rc < 0) {
+        error_exit(errno, __func__);
+    }
+}
+
 void qemu_thread_create(QemuThread *thread,
                        void *(*start_routine)(void*),
                        void *arg, int mode)

qemu-thread-posix.h

@@ -1,6 +1,7 @@
 #ifndef __QEMU_THREAD_POSIX_H
 #define __QEMU_THREAD_POSIX_H 1
 #include "pthread.h"
+#include <semaphore.h>
 
 struct QemuMutex {
     pthread_mutex_t lock;
@@ -10,6 +11,10 @@ struct QemuCond {
     pthread_cond_t cond;
 };
 
+struct QemuSemaphore {
+    sem_t sem;
+};
+
 struct QemuThread {
     pthread_t thread;
 };

qemu-thread-win32.c

@@ -192,6 +192,41 @@ void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex)
     qemu_mutex_lock(mutex);
 }
 
+void qemu_sem_init(QemuSemaphore *sem, int init)
+{
+    /* Manual reset.  */
+    sem->sema = CreateSemaphore(NULL, init, LONG_MAX, NULL);
+}
+
+void qemu_sem_destroy(QemuSemaphore *sem)
+{
+    CloseHandle(sem->sema);
+}
+
+void qemu_sem_post(QemuSemaphore *sem)
+{
+    ReleaseSemaphore(sem->sema, 1, NULL);
+}
+
+int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
+{
+    int rc = WaitForSingleObject(sem->sema, ms);
+    if (rc == WAIT_OBJECT_0) {
+        return 0;
+    }
+    if (rc != WAIT_TIMEOUT) {
+        error_exit(GetLastError(), __func__);
+    }
+    return -1;
+}
+
+void qemu_sem_wait(QemuSemaphore *sem)
+{
+    if (WaitForSingleObject(sem->sema, INFINITE) != WAIT_OBJECT_0) {
+        error_exit(GetLastError(), __func__);
+    }
+}
+
 struct QemuThreadData {
     /* Passed to win32_start_routine.  */
     void             *(*start_routine)(void *);

qemu-thread-win32.h

@@ -13,6 +13,10 @@ struct QemuCond {
     HANDLE continue_event;
 };
 
+struct QemuSemaphore {
+    HANDLE sema;
+};
+
 typedef struct QemuThreadData QemuThreadData;
 struct QemuThread {
     QemuThreadData *data;

qemu-thread.h

@@ -6,6 +6,7 @@
 
 typedef struct QemuMutex QemuMutex;
 typedef struct QemuCond QemuCond;
+typedef struct QemuSemaphore QemuSemaphore;
 typedef struct QemuThread QemuThread;
 
 #ifdef _WIN32
@@ -38,6 +39,12 @@ void qemu_cond_signal(QemuCond *cond);
 void qemu_cond_broadcast(QemuCond *cond);
 void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex);
 
+void qemu_sem_init(QemuSemaphore *sem, int init);
+void qemu_sem_post(QemuSemaphore *sem);
+void qemu_sem_wait(QemuSemaphore *sem);
+int qemu_sem_timedwait(QemuSemaphore *sem, int ms);
+void qemu_sem_destroy(QemuSemaphore *sem);
+
 void qemu_thread_create(QemuThread *thread,
                         void *(*start_routine)(void *),
                         void *arg, int mode);