MINOR: sched: pass the thread number to is_sched_alive()

Now it will be possible to query any thread's scheduler state, not
only the current one. This aims at simplifying the watchdog checks
for reported threads. The operation is now a simple atomic xchg.

include/haproxy/task.h

@@ -123,11 +123,11 @@ void wake_expired_tasks(void);
  */
 int next_timer_expiry(void);
 
-/* Pings the scheduler to verify that tasks continue running.
- * Returns 1 if the scheduler made progress since last call,
- * 0 if it looks stuck.
+/* Pings the scheduler to verify that tasks continue running for thread <thr>.
+ * Returns 1 if the scheduler made progress since last call, 0 if it looks
+ * stuck. It marks it as stuck for next visit.
  */
-int is_sched_alive(void);
+int is_sched_alive(int thr);
 
 /*
  * Delete every tasks before running the master polling loop

src/task.c

@@ -910,18 +910,13 @@ void process_runnable_tasks()
 		activity[tid].long_rq++;
 }
 
-/* Pings the scheduler to verify that tasks continue running.
- * Returns 1 if the scheduler made progress since last call,
- * 0 if it looks stuck.
+/* Pings the scheduler to verify that tasks continue running for thread <thr>.
+ * Returns 1 if the scheduler made progress since last call, 0 if it looks
+ * stuck. It marks it as stuck for next visit.
  */
-int is_sched_alive(void)
+int is_sched_alive(int thr)
 {
-	if (sched_ctx[tid].sched_stuck)
-		return 0;
-
-	/* next time we'll know if any progress was made */
-	sched_ctx[tid].sched_stuck = 1;
-	return 1;
+	return !HA_ATOMIC_XCHG(&sched_ctx[thr].sched_stuck, 1);
 }
 
 /*

src/wdt.c

@@ -189,7 +189,7 @@ void wdt_handler(int sig, siginfo_t *si, void *arg)
 	if (_HA_ATOMIC_LOAD(&th_ctx->flags) & TH_FL_STUCK)
 		ha_panic();
 
-	if (!is_sched_alive())
+	if (!is_sched_alive(thr))
 		ha_stuck_warning();
 
 	/* let's go on */