Re: [PATCH] nohz: Make tick_nohz_irq_exit() irq safe
From: Thomas Gleixner
Date: Thu Feb 21 2013 - 11:46:30 EST
On Thu, 21 Feb 2013, Frederic Weisbecker wrote:
> 2013/2/21 Thomas Gleixner <tglx@xxxxxxxxxxxxx>:
> > On Wed, 20 Feb 2013, Frederic Weisbecker wrote:
> >> 2013/2/20 Thomas Gleixner <tglx@xxxxxxxxxxxxx>:
> >> > That's not a fix. That's an hack.
> >> I know it looks that way. That's because it's a pure regression fix,
> >> minimal for backportability.
> >> I'm distinguishing two different things here: the fact that some archs
> >> can call irq_exit() with interrupts enabled which is a global design
> >> problem, and the fact that tick_nohz_irq_exit() was safe against that
> >> until 3.2 when I broke it with a commit of mine.
> >> My goal was basically to restore that protection in a minimal commit
> >> such that we can backport the regression fix, then deal with
> >> __ARCH_IRQ_EXIT_IRQS_DISABLED afterward, since it requires some more
> >> invasive changes.
> >> >> A saner long term solution will be to remove
> >> >> __ARCH_IRQ_EXIT_IRQS_DISABLED.
> >> >
> >> > We really want to enforce that interrupt disabled condition for
> >> > calling irq_exit(). So why make this exclusive to tick_nohz_irq_exit()?
> >> I need a fix that I can backport. Is the below fine with a stable tag?
> >> It looks a bit too invasive for the single regression involved.
> > I think that's fine as it's obviously correct and not diluting the
> > real underlying issue of the __ARCH_IRQ_EXIT_IRQS_DISABLED insanity.
> Ok fine. Do you plan to commit your proposed change then?
Second thoughts. I probably go for your minimal fix for stable and
then push my version on top of it to Linus only.
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