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Message-ID: <1276790557.27822.516.camel@twins>
Date:	Thu, 17 Jun 2010 18:02:37 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Brian Bloniarz <bmb@...enacr.com>
Cc:	Mike Galbraith <efault@....de>, Jiri Kosina <jkosina@...e.cz>,
	Chris Wedgwood <cw@...f.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg KH <gregkh@...e.de>, Alan Cox <alan@...rguk.ukuu.org.uk>,
	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
	Jef Driesen <jefdriesen@...enet.be>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] nohz: Fix nohz ratelimit

Chris Wedgwood reports that 39c0cbe (sched: Rate-limit nohz) causes a
serial console regression, unresponsiveness, and indeed it does. The
below fixes it by not skipping out when the tick has been stopped.

Reported-by: Chris Wedgwood <cw@...f.org>
Tested-by: Brian Bloniarz <bmb@...enacr.com>
Signed-off-by: Mike Galbraith <efault@....de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
 kernel/time/tick-sched.c |    5 +----
 1 files changed, 1 insertions(+), 4 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 5f171f0..e0707ea 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -315,9 +315,6 @@ void tick_nohz_stop_sched_tick(int inidle)
 		goto end;
 	}
 
-	if (nohz_ratelimit(cpu))
-		goto end;
-
 	ts->idle_calls++;
 	/* Read jiffies and the time when jiffies were updated last */
 	do {
@@ -328,7 +325,7 @@ void tick_nohz_stop_sched_tick(int inidle)
 	} while (read_seqretry(&xtime_lock, seq));
 
 	if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu) ||
-	    arch_needs_cpu(cpu)) {
+	    arch_needs_cpu(cpu) || nohz_ratelimit(cpu)) {
 		next_jiffies = last_jiffies + 1;
 		delta_jiffies = 1;
 	} else {

--
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