linux-kernel - [PATCH] sched: report correct state for TASK_IDLE

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Message-id: <169335025927.5133.4781141800413736103@noble.neil.brown.name>
Date:   Wed, 30 Aug 2023 09:04:19 +1000
From:   NeilBrown <neilb@...e.de>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
cc:     Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        linux-kernel@...r.kernel.org, Chuck Lever <chuck.lever@...cle.com>,
        linux-nfs@...r.kernel.org
Subject: [PATCH] sched: report correct state for TASK_IDLE | TASK_FREEZABLE


task_state_index() ignores uninteresting state flags (such as
TASK_FREEZABLE) for most states, but for TASK_IDLE and TASK_RTLOCK_WAIT
it does not.
So if a task is waiting TASK_IDLE|TASK_FREEZABLE it gets incorrectly
reported as TASK_UNINTERRUPTIBLE or "D".  (it is planned for nfsd to
change to use this state).

Fix this by only testing the interesting bits and not the irrelevant
bits in __task_state_index()

Signed-off-by: NeilBrown <neilb@...e.de>
---
 include/linux/sched.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 177b3f3676ef..c0a21a3b106c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1671,7 +1671,7 @@ static inline unsigned int __task_state_index(unsigned int tsk_state,
 
 	BUILD_BUG_ON_NOT_POWER_OF_2(TASK_REPORT_MAX);
 
-	if (tsk_state == TASK_IDLE)
+	if ((tsk_state & TASK_IDLE) == TASK_IDLE)
 		state = TASK_REPORT_IDLE;
 
 	/*
@@ -1679,7 +1679,7 @@ static inline unsigned int __task_state_index(unsigned int tsk_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)
+	if (tsk_state & TASK_RTLOCK_WAIT)
 		state = TASK_UNINTERRUPTIBLE;
 
 	return fls(state);
-- 
2.41.0