Add and use fiber_cond_wait_deadline

Like fiber_cond_wait_timeout(), but waits for a deadline to pass.

Follow-up b4bf3fa0 ("applier: use fiber_cond instead of fiber_channel");

src/box/applier.cc

@@ -702,13 +702,12 @@ static inline int
 applier_wait_for_state(struct applier_on_state *trigger, double timeout)
 {
 	struct applier *applier = trigger->applier;
+	double deadline = ev_monotonic_now(loop()) + timeout;
 	while (applier->state != APPLIER_OFF &&
 	       applier->state != APPLIER_STOPPED &&
 	       applier->state != trigger->desired_state) {
-		double wait_start = ev_monotonic_now(loop());
-		if (fiber_cond_wait_timeout(&trigger->wakeup, timeout) != 0)
+		if (fiber_cond_wait_deadline(&trigger->wakeup, deadline) != 0)
 			return -1; /* ER_TIMEOUT */
-		timeout -= ev_monotonic_now(loop()) - wait_start;
 	}
 	if (applier->state != trigger->desired_state) {
 		assert(applier->state == APPLIER_OFF ||

src/box/vy_quota.h

@@ -148,13 +148,11 @@ vy_quota_release(struct vy_quota *q, size_t size)
 static inline int
 vy_quota_use(struct vy_quota *q, size_t size, double timeout)
 {
+	double deadline = ev_monotonic_now(loop()) + timeout;
 	while (q->used + size > q->limit && timeout > 0) {
 		q->quota_exceeded_cb(q);
-		double wait_start = ev_monotonic_now(loop());
-		if (fiber_cond_wait_timeout(&q->cond, timeout) != 0)
+		if (fiber_cond_wait_deadline(&q->cond, deadline) != 0)
 			break; /* timed out */
-		double wait_end = ev_monotonic_now(loop());
-		timeout -= (wait_end - wait_start);
 	}
 	if (q->used + size > q->limit)
 		return -1;

src/fiber_cond.c

@@ -116,3 +116,10 @@ fiber_cond_wait(struct fiber_cond *c)
 {
 	return fiber_cond_wait_timeout(c, TIMEOUT_INFINITY);
 }
+
+int
+fiber_cond_wait_deadline(struct fiber_cond *c, double deadline)
+{
+	double timeout = deadline - ev_monotonic_now(loop());
+	return fiber_cond_wait_timeout(c, timeout);
+}

src/fiber_cond.h

@@ -128,6 +128,15 @@ fiber_cond_wait(struct fiber_cond *cond);
 
 /** \endcond public */
 
+/**
+ * Wait until the given condition variable is signaled or the
+ * deadline passed. The deadline is specified as absolute time
+ * in seconds since system start (i.e. monotonic clock).
+ * @see fiber_cond_wait_timeout()
+ */
+int
+fiber_cond_wait_deadline(struct fiber_cond *cond, double deadline);
+
 #if defined(__cplusplus)
 } /* extern "C" */
 #endif /* defined(__cplusplus) */