linux-kernel - Re: [PATCH RFC] irq_work: Warn if there's still work on cpu

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Date:	Thu, 15 Nov 2012 19:12:33 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: Re: [PATCH RFC] irq_work: Warn if there's still work on cpu_down

2012/11/15 Steven Rostedt <rostedt@...dmis.org>:
> If we are in nohz and there's still irq_work to be done when the idle
> task is about to go offline. Give a nasty warning.
>
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
>
> Index: linux-rt.git/kernel/irq_work.c
> ===================================================================
> --- linux-rt.git.orig/kernel/irq_work.c
> +++ linux-rt.git/kernel/irq_work.c
> @@ -103,6 +103,9 @@ bool irq_work_needs_cpu(void)
>         if (llist_empty(this_list))
>                 return false;
>
> +       /* All work should have been flushed before going offline */
> +       WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));

Should we return false in that case? I don't know what can happen if
we wait for one more tick while the CPU is offline and apic is
deactivated.

> +
>         return true;
>  }
>
>
>
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