Commit 59bf61d1 authored May 07, 2015 by Thomas Gleixner Committed by Sanrio Alvares Sep 09, 2015

nohz: Fix !HIGH_RES_TIMERS hang



Simon Horman reported this crash on a system with
high-res timers disabled but nohz enabled:

  > ------------[ cut here ]------------
  > kernel BUG at kernel/irq_work.c:135!

    BUG_ON(!irqs_disabled());

So something enabled interrupts in the periodic tick handling machinery,
and that code path indeed has a local_irq_disable()/enable pair in
tick_nohz_switch_to_nohz() which causes havoc. Fix it.

This patch also fixes a +nohz -hrtimers hang reported by Ingo Molnar.

Change-Id: If3d528d940b20bca12c8d2b15bcef9774605fa00
Reported-by: Simon Horman <horms@verge.net.au>
Reported-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: LAK <linux-arm-kernel@lists.infradead.org>
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1505071425520.4225@nanos


Signed-off-by: Ingo Molnar <mingo@kernel.org>
Git-commit: 6b442bc81337913eb775965a67ffdb8a36935422
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git


[salvares@codeaurora.org: resolved context conflicts in tick-sched.c]
Signed-off-by: Sanrio Alvares <salvares@codeaurora.org>

parent c8df36dc

kernel/time/tick-sched.c

+3 −6

Original line number	Diff line number	Diff line
		@@ -1058,11 +1058,9 @@ static void tick_nohz_switch_to_nohz(void)
		if (!tick_nohz_enabled)
		return;

		local_irq_disable();
		if (tick_switch_to_oneshot(tick_nohz_handler)) {
		local_irq_enable();
		if (tick_switch_to_oneshot(tick_nohz_handler))
		return;
		}

		tick_nohz_active = 1;
		ts->nohz_mode = NOHZ_MODE_LOWRES;

		@@ -1080,7 +1078,6 @@ static void tick_nohz_switch_to_nohz(void)
		break;
		next = ktime_add(next, tick_period);
		}
		local_irq_enable();
		}

		/*
		@@ -1331,7 +1328,7 @@ void tick_oneshot_notify(void)
		* Called cyclic from the hrtimer softirq (driven by the timer
		* softirq) allow_nohz signals, that we can switch into low-res nohz
		* mode, because high resolution timers are disabled (either compile
		* or runtime).
		* or runtime). Called with interrupts disabled.
		*/
		int tick_check_oneshot_change(int allow_nohz)
		{