linux-kernel - [PATCH 4.12 175/196] sched/cputime: Always set tsk->vtime_snap

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Message-Id: <20170725192054.652244289@linuxfoundation.org>
Date:   Tue, 25 Jul 2017 12:22:54 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Luiz Capitulino <lcapitulino@...hat.com>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Rik van Riel <riel@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Wanpeng Li <kernellwp@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Mel Gorman <mgorman@...hsingularity.net>
Subject: [PATCH 4.12 175/196] sched/cputime: Always set tsk->vtime_snap_whence after accounting vtime

4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Frederic Weisbecker <fweisbec@...il.com>

commit 9fa57cf5a5c4aed1e45879b335fe433048709327 upstream.

Even though it doesn't have functional consequences, setting
the task's new context state after we actually accounted the pending
vtime from the old context state makes more sense from a review
perspective.

vtime_user_exit() is the only function that doesn't follow that rule
and that can bug the reviewer for a little while until he realizes there
is no reason for this special case.

Tested-by: Luiz Capitulino <lcapitulino@...hat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Rik van Riel <riel@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Wanpeng Li <kernellwp@...il.com>
Link: http://lkml.kernel.org/r/1498756511-11714-3-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/sched/cputime.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -736,9 +736,9 @@ void vtime_user_enter(struct task_struct
 void vtime_user_exit(struct task_struct *tsk)
 {
 	write_seqcount_begin(&tsk->vtime_seqcount);
-	tsk->vtime_snap_whence = VTIME_SYS;
 	if (vtime_delta(tsk))
 		account_user_time(tsk, get_vtime_delta(tsk));
+	tsk->vtime_snap_whence = VTIME_SYS;
 	write_seqcount_end(&tsk->vtime_seqcount);
 }