From: Thomas Gleixner <tglx@linutronix.de>
Date: Fri, 29 Nov 2013 11:18:13 +0000 (+0100)
Subject: nohz: Fix another inconsistency between CONFIG_NO_HZ=n and nohz=off
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=ec804bd9e1ecad7a6d9f9428eaf388e3dac9cb63;p=GitHub%2Fmt8127%2Fandroid_kernel_alcatel_ttab.git

nohz: Fix another inconsistency between CONFIG_NO_HZ=n and nohz=off

commit 0e576acbc1d9600cf2d9b4a141a2554639959d50 upstream.

If CONFIG_NO_HZ=n tick_nohz_get_sleep_length() returns NSEC_PER_SEC/HZ.

If CONFIG_NO_HZ=y and the nohz functionality is disabled via the
command line option "nohz=off" or not enabled due to missing hardware
support, then tick_nohz_get_sleep_length() returns 0. That happens
because ts->sleep_length is never set in that case.

Set it to NSEC_PER_SEC/HZ when the NOHZ mode is inactive.

Reported-by: Michal Hocko <mhocko@suse.cz>
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Rui Xiang <rui.xiang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 4251374578bc..67f7a2d2efbc 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -720,8 +720,10 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
 		return false;
 	}
 
-	if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
+	if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) {
+		ts->sleep_length = (ktime_t) { .tv64 = NSEC_PER_SEC/HZ };
 		return false;
+	}
 
 	if (need_resched())
 		return false;