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Commit 3310d4d3 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Thomas Gleixner
Browse files

nohz: Fix nohz ratelimit 



Chris Wedgwood reports that 39c0cbe2 (sched: Rate-limit nohz) causes a
serial console regression, unresponsiveness, and indeed it does. The
reason is that the nohz code is skipped even when the tick was already
stopped before the nohz_ratelimit(cpu) condition changed.

Move the nohz_ratelimit() check to the other conditions which prevent
long idle sleeps.

Reported-by: default avatarChris Wedgwood <cw@f00f.org>
Tested-by: default avatarBrian Bloniarz <bmb@athenacr.com>
Signed-off-by: default avatarMike Galbraith <efault@gmx.de>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Greg KH <gregkh@suse.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Jef Driesen <jefdriesen@telenet.be>
LKML-Reference: <1276790557.27822.516.camel@twins>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 7e27d6e7

kernel/time/tick-sched.c

+1 −4
Original line number Diff line number Diff line
@@ -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 {