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From: Chris Friesen <cbf123@mail.usask.ca>
To: John Stultz <john.stultz@linaro.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	lkml <linux-kernel@vger.kernel.org>
Subject: [PATCH] steal_account_process_tick() should return jiffies
Date: Fri, 04 Mar 2016 16:59:05 -0600	[thread overview]
Message-ID: <56DA1339.5030601@mail.usask.ca> (raw)

The callers of steal_account_process_tick() expect it to return whether
the last jiffy was stolen or not.
    
Currently the return value of steal_account_process_tick() is in units
of cputime, which vary between either jiffies or nsecs depending on
CONFIG_VIRT_CPU_ACCOUNTING_GEN.
    
The fix is to change steal_account_process_tick() to always return
jiffies.  If CONFIG_VIRT_CPU_ACCOUNTING_GEN is not enabled then this
is a no-op.

As far as I can tell this bug has been present since commit dee08a72.

Signed-off-by: Chris Friesen <chris.friesen@windriver.com>
---

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

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index b2ab2ff..e724496 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -276,7 +276,7 @@ static __always_inline bool steal_account_process_tick(void)
 		this_rq()->prev_steal_time += cputime_to_nsecs(steal_ct);
 
 		account_steal_time(steal_ct);
-		return steal_ct;
+		return cputime_to_jiffies(steal_ct);
 	}
 #endif
 	return false;

             reply	other threads:[~2016-03-04 23:07 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-04 22:59 Chris Friesen [this message]
2016-03-05 10:27 ` [PATCH] steal_account_process_tick() should return jiffies Thomas Gleixner
2016-03-05 13:19   ` Frederic Weisbecker
2016-03-06  4:17     ` Chris Friesen
2016-03-06  5:18       ` [PATCH v2] sched/cputime: " Chris Friesen
2016-03-06 10:58         ` Thomas Gleixner
2016-03-08 12:29         ` Frederic Weisbecker
2016-03-08 13:18         ` [tip:sched/core] sched/cputime: Fix steal_account_process_tick() to always " tip-bot for Chris Friesen

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