Only notify the first 5 pending lock waiters. This avoids a thundering herd
problem that is really nasty in a cluster. It also makes acquiring a lock a bit
more FIFO, lock waiters are added to the end of the array.
}
if ((lock_type & G_LOCK_PENDING) == 0) {
+ int num_wakeups = 0;
+
/*
- * We've been the lock holder. Tell all others to retry.
+ * We've been the lock holder. Others to retry. Don't
+ * tell all others to avoid a thundering herd. In case
+ * this leads to a complete stall because we miss some
+ * processes, the loop in g_lock_lock tries at least
+ * once a minute.
*/
+
for (i=0; i<num_locks; i++) {
if ((locks[i].lock_type & G_LOCK_PENDING) == 0) {
continue;
}
+ if (!process_exists(locks[i].pid)) {
+ continue;
+ }
/*
* Ping all waiters to retry
procid_str(talloc_tos(),
&locks[i].pid),
nt_errstr(status)));
+ } else {
+ num_wakeups += 1;
+ }
+ if (num_wakeups > 5) {
+ break;
}
}
}