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

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Message-ID: <1353005806.18025.111.camel@gandalf.local.home>
Date:	Thu, 15 Nov 2012 13:56:46 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
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

On Thu, 2012-11-15 at 19:12 +0100, Frederic Weisbecker wrote:
> 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.
> 

We can just let it go and find out :-)

Heck, they get the warning, if the system crashes shortly afterwards,
they know why.

-- Steve

> > +
> >         return true;
> >  }
> >
> >
> >


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