Message-ID: <56DA1339.5030601@mail.usask.ca>
Date: Fri, 04 Mar 2016 16:59:05 -0600
From: Chris Friesen <cbf123@mail.usask.ca>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0
MIME-Version: 1.0
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
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1064
Lines: 32

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;