qemu_event_timedwait() is equivalent to qemu_event_wait(), except it has
a relative timeout.

Signed-off-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
---
 include/qemu/thread-posix.h | 11 +++++++++++
 include/qemu/thread.h       |  8 +++++++-
 util/event.c                | 34 +++++++++++++++++++++++++++++-----
 util/qemu-thread-posix.c    | 11 +----------
 4 files changed, 48 insertions(+), 16 deletions(-)

diff --git a/include/qemu/thread-posix.h b/include/qemu/thread-posix.h
index 758808b705e4..11193b1580f8 100644
--- a/include/qemu/thread-posix.h
+++ b/include/qemu/thread-posix.h
@@ -36,4 +36,15 @@ struct QemuThread {
     pthread_t thread;
 };
 
+static inline clockid_t qemu_timedwait_clockid(void)
+{
+#ifdef CONFIG_PTHREAD_CONDATTR_SETCLOCK
+    return CLOCK_MONOTONIC;
+#else
+    return CLOCK_REALTIME;
+#endif
+}
+
+void compute_abs_deadline(struct timespec *ts, int ms);
+
 #endif
diff --git a/include/qemu/thread.h b/include/qemu/thread.h
index f0302ed01fdb..3030458bb666 100644
--- a/include/qemu/thread.h
+++ b/include/qemu/thread.h
@@ -201,7 +201,13 @@ void qemu_sem_destroy(QemuSemaphore *sem);
 void qemu_event_init(QemuEvent *ev, bool init);
 void qemu_event_set(QemuEvent *ev);
 void qemu_event_reset(QemuEvent *ev);
-void qemu_event_wait(QemuEvent *ev);
+bool qemu_event_timedwait(QemuEvent *ev, int ms);
+
+static inline void qemu_event_wait(QemuEvent *ev)
+{
+    qemu_event_timedwait(ev, INT_MAX);
+}
+
 void qemu_event_destroy(QemuEvent *ev);
 
 void qemu_thread_create(QemuThread *thread, const char *name,
diff --git a/util/event.c b/util/event.c
index 5a8141cd0e46..e22cc08a629b 100644
--- a/util/event.c
+++ b/util/event.c
@@ -33,7 +33,15 @@ void qemu_event_init(QemuEvent *ev, bool init)
 {
 #ifndef HAVE_FUTEX
     pthread_mutex_init(&ev->lock, NULL);
+#ifdef CONFIG_PTHREAD_CONDATTR_SETCLOCK
+    pthread_condattr_t attr;
+    pthread_condattr_init(&attr);
+    pthread_condattr_setclock(&attr, qemu_timedwait_clockid());
+    pthread_cond_init(&ev->cond, &attr);
+    pthread_condattr_destroy(&attr);
+#else
     pthread_cond_init(&ev->cond, NULL);
+#endif
 #endif
 
     ev->value = (init ? EV_SET : EV_FREE);
@@ -121,15 +129,17 @@ void qemu_event_reset(QemuEvent *ev)
 #endif
 }
 
-void qemu_event_wait(QemuEvent *ev)
+bool qemu_event_timedwait(QemuEvent *ev, int ms)
 {
     assert(ev->initialized);
 
 #ifdef HAVE_FUTEX
+    int64_t deadline = get_clock() + (int64_t)ms * SCALE_MS;
+
     while (true) {
         /*
-         * qemu_event_wait must synchronize with qemu_event_set even if it does
-         * not go down the slow path, so this load-acquire is needed that
+         * qemu_event_timedwait must synchronize with qemu_event_set even if it
+         * does not go down the slow path, so this load-acquire is needed that
          * synchronizes with the first memory barrier in qemu_event_set().
          */
         unsigned value = qatomic_load_acquire(&ev->value);
@@ -159,13 +169,27 @@ void qemu_event_wait(QemuEvent *ev)
          * a smp_mb() pairing with the second barrier of qemu_event_set().
          * The barrier is inside the FUTEX_WAIT system call.
          */
-        qemu_futex_wait(ev, EV_BUSY);
+        if (!qemu_futex_timedwait(ev, EV_BUSY, deadline)) {
+            return false;
+        }
     }
+
+    return true;
 #else
+    bool failed;
+    struct timespec ts;
+
+    compute_abs_deadline(&ts, ms);
+
     pthread_mutex_lock(&ev->lock);
     while (qatomic_read(&ev->value) != EV_SET) {
-        pthread_cond_wait(&ev->cond, &ev->lock);
+        failed = pthread_cond_timedwait(&ev->cond, &ev->lock, &ts);
+        if (failed) {
+            break;
+        }
     }
     pthread_mutex_unlock(&ev->lock);
+
+    return !failed;
 #endif
 }
diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index ba725444ba63..f649bfa00015 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -44,16 +44,7 @@ static void error_exit(int err, const char *msg)
     abort();
 }
 
-static inline clockid_t qemu_timedwait_clockid(void)
-{
-#ifdef CONFIG_PTHREAD_CONDATTR_SETCLOCK
-    return CLOCK_MONOTONIC;
-#else
-    return CLOCK_REALTIME;
-#endif
-}
-
-static void compute_abs_deadline(struct timespec *ts, int ms)
+void compute_abs_deadline(struct timespec *ts, int ms)
 {
     clock_gettime(qemu_timedwait_clockid(), ts);
     ts->tv_nsec += (ms % 1000) * 1000000;

-- 
2.51.0