[PATCH] arm_timer: remove a racy and obsolete PF_EXITING check

arm_timer() checks PF_EXITING to prevent BUG_ON(->exit_state)
in run_posix_cpu_timers().

However, for some reason it does so only for CPUCLOCK_PERTHREAD
case (which is imho wrong).

Also, this check is not reliable, PF_EXITING could be set on
another cpu without any locks/barriers just after the check,
so it can't prevent from attaching the timer to the exiting
task.

The previous patch makes this check unneeded.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/posix-cpu-timers.c

@@ -555,9 +555,6 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
 	struct cpu_timer_list *next;
 	unsigned long i;
 
-	if (CPUCLOCK_PERTHREAD(timer->it_clock)	&& (p->flags & PF_EXITING))
-		return;
-
 	head = (CPUCLOCK_PERTHREAD(timer->it_clock) ?
 		p->cpu_timers : p->signal->cpu_timers);
 	head += CPUCLOCK_WHICH(timer->it_clock);