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Re: [PATCH v3 03/11] ARC: Allow irq threading

From	Thomas Gleixner <tglx@linutronix.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH v3 03/11] ARC: Allow irq threading
Date	2017-08-25 23:10 +0200
Message-ID	<uiu1A-Hq-29@gated-at.bofh.it> (permalink)
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On Fri, 25 Aug 2017, Thomas Gleixner wrote:

> On Fri, 25 Aug 2017, Vineet Gupta wrote:
> > On 06/15/2017 01:43 AM, Noam Camus wrote:
> > > From: Noam Camus <noamc@ezchip.com>
> > > 
> > > Working with NPS400 we noticed that there is a possibility of L1
> > > interrupt nesting that may run out kernel stack.
> > > The scenario include serving invoke_softirqs() from irq_exit()
> > > and once local_irq_enable() called can hit another one before we
> > > managed to restore last one and pop some place from kernel stack.
> > > 
> > > Serving softirqs at dedicated kernel thread may mitigate this.
> > > We see that many architectures, including x86, behave like this.
> 
> Well, no. x86 supports that, but that does not mean many user add it to the
> command line.

The real fix for that is to use dedicated irq and softirq stacks instead of
using the potentially deep thread stack for everything. That's what x86 and
others do unconditinally.

Thanks,

	tglx

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Re: [PATCH v3 03/11] ARC: Allow irq threading Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2017-08-25 22:50 +0200
  Re: [PATCH v3 03/11] ARC: Allow irq threading Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 23:00 +0200
    Re: [PATCH v3 03/11] ARC: Allow irq threading Thomas Gleixner <tglx@linutronix.de> - 2017-08-25 23:10 +0200

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