Commit 25795ef6 authored by Valentin Schneider's avatar Valentin Schneider Committed by Peter Zijlstra
Browse files

sched/tracing: Report TASK_RTLOCK_WAIT tasks as TASK_UNINTERRUPTIBLE 



TASK_RTLOCK_WAIT currently isn't part of TASK_REPORT, thus a task blocking
on an rtlock will appear as having a task state == 0, IOW TASK_RUNNING.

The actual state is saved in p->saved_state, but reading it after reading
p->__state has a few issues:
o that could still be TASK_RUNNING in the case of e.g. rt_spin_lock
o ttwu_state_match() might have changed that to TASK_RUNNING

As pointed out by Eric, adding TASK_RTLOCK_WAIT to TASK_REPORT implies
exposing a new state to userspace tools which way not know what to do with
them. The only information that needs to be conveyed here is that a task is
waiting on an rt_mutex, which matches TASK_UNINTERRUPTIBLE - there's no
need for a new state.

Reported-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: default avatarValentin Schneider <valentin.schneider@arm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20220120162520.570782-3-valentin.schneider@arm.com
parent fa2c3254

include/linux/sched.h

+8 −0
Original line number Diff line number Diff line
@@ -1630,6 +1630,14 @@ static inline unsigned int __task_state_index(unsigned int tsk_state, 
	if (tsk_state == TASK_IDLE)

		state = TASK_REPORT_IDLE;



	/*

	 * We're lying here, but rather than expose a completely new task state

	 * to userspace, we can make this appear as if the task has gone through

	 * a regular rt_mutex_lock() call.

	 */

	if (tsk_state == TASK_RTLOCK_WAIT)

		state = TASK_UNINTERRUPTIBLE;



	return fls(state);

}