[06/19] multipathd: generalize and fix wait_for_state_change_if()

Commit Message

Martin Wilck Sept. 16, 2020, 3:37 p.m. UTC

From: Martin Wilck <[e-mail]>

It's unlikely but not impossible that other threads change the state
while we're waiting, and if we grab the lock again, it's still not
what we wanted. We need to continue waiting until either the condition
is met, or time timeout expired.

Moreover, generalize this code so that it can also be used in
set_config_state().

Signed-off-by: Martin Wilck <[e-mail]>
---
 multipathd/main.c | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

Patch

diff --git a/multipathd/main.c b/multipathd/main.c
index 451d68c..49809e0 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -223,6 +223,23 @@  static void config_cleanup(__attribute__((unused)) void *arg)
 	pthread_mutex_unlock(&config_lock);
 }
 
+#define __wait_for_state_change(condition, ms)				\
+	({								\
+		struct timespec tmo;					\
+		int rc = 0;						\
+									\
+		if (condition) {					\
+			get_monotonic_time(&tmo);			\
+			tmo.tv_nsec += (ms) * 1000 * 1000;		\
+			normalize_timespec(&tmo);			\
+			do						\
+				rc = pthread_cond_timedwait(		\
+					&config_cond, &config_lock, &tmo); \
+			while (rc == 0 && (condition));			\
+		}							\
+		rc;							\
+	})
+
 /*
  * If the current status is @oldstate, wait for at most @ms milliseconds
  * for the state to change, and return the new state, which may still be
@@ -232,20 +249,14 @@  enum daemon_status wait_for_state_change_if(enum daemon_status oldstate,
 					    unsigned long ms)
 {
 	enum daemon_status st;
-	struct timespec tmo;
 
 	if (oldstate == DAEMON_SHUTDOWN)
 		return DAEMON_SHUTDOWN;
 
 	pthread_mutex_lock(&config_lock);
 	pthread_cleanup_push(config_cleanup, NULL);
+	__wait_for_state_change(running_state == oldstate, ms);
 	st = running_state;
-	if (st == oldstate && clock_gettime(CLOCK_MONOTONIC, &tmo) == 0) {
-		tmo.tv_nsec += ms * 1000 * 1000;
-		normalize_timespec(&tmo);
-		(void)pthread_cond_timedwait(&config_cond, &config_lock, &tmo);
-		st = running_state;
-	}
 	pthread_cleanup_pop(1);
 	return st;
 }