poll/select: initialize triggered field of struct poll_wqueues

The triggered field of struct poll_wqueues introduced in commit
5f820f648c92a5ecc771a96b3c29aa6e90013bba ("poll: allow f_op->poll to
sleep").

It was first set to 1 in pollwake() (now __pollwake() ), tested and
later set to 0 in poll_schedule_timeout(), but not initialized before.

As a result when the process needs to sleep, triggered was likely to be
non-zero even if pollwake() is not called before the first
poll_schedule_timeout(), meaning schedule_hrtimeout_range() would not be
called and an extra loop calling all ->poll() would be done.

This patch initialize triggered to 0 in poll_initwait() so the ->poll()
are not called twice before the process goes to sleep when it needs to.

Signed-off-by: Guillaume Knispel <gknispel@proformatique.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/select.c

@@ -110,6 +110,7 @@ void poll_initwait(struct poll_wqueues *pwq)
 {
 	init_poll_funcptr(&pwq->pt, __pollwait);
 	pwq->polling_task = current;
+	pwq->triggered = 0;
 	pwq->error = 0;
 	pwq->table = NULL;
 	pwq->inline_index = 0;