linux-kernel - Re: [patch V2 2/6] genirq: Fix misleading synchronize

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Message-ID: <alpine.DEB.2.21.1907011959410.1802@nanos.tec.linutronix.de>
Date:   Mon, 1 Jul 2019 20:01:24 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Marc Zyngier <marc.zyngier@....com>
Subject: Re: [patch V2 2/6] genirq: Fix misleading synchronize_irq()
 documentation

On Mon, 1 Jul 2019, Peter Zijlstra wrote:

> On Fri, Jun 28, 2019 at 01:11:50PM +0200, Thomas Gleixner wrote:
> > The function might sleep, so it cannot be called from interrupt
> > context. Not even with care.
> > 
> > Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> > ---
> >  kernel/irq/manage.c |    3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > --- a/kernel/irq/manage.c
> > +++ b/kernel/irq/manage.c
> > @@ -96,7 +96,8 @@ EXPORT_SYMBOL(synchronize_hardirq);
> >   *	to complete before returning. If you use this function while
> >   *	holding a resource the IRQ handler may need you will deadlock.
> >   *
> > - *	This function may be called - with care - from IRQ context.
> > + *	Can only be called from preemptible code as it might sleep when
> > + *	an interrupt thread is associated to @irq.
> >   */
> >  void synchronize_irq(unsigned int irq)
> >  {
> 
> +	might_sleep();
> 
> ?

  ....

	wait_event()
	  might_sleep() ...

?