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From: Arnd Bergmann <arnd@arndb.de>
To: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 2/2] arm64: support HAVE_IRQ_EXIT_ON_IRQ_STACK
Date: Thu, 7 Jul 2022 22:55:45 +0200	[thread overview]
Message-ID: <CAK8P3a1GgnmhHj+_gRYZ52=TvfBQb_xxYt1Hg-jMJ2gZqCD42w@mail.gmail.com> (raw)
In-Reply-To: <33a63e76-fb71-2b9e-3b3c-cc6f7a675cf3@bytedance.com>

On Thu, Jul 7, 2022 at 5:00 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote:
> On 2022/7/7 22:41, Arnd Bergmann wrote:
> > On Thu, Jul 7, 2022 at 3:38 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote:
> >> On 2022/7/7 20:49, Arnd Bergmann wrote:
> >
> > -asmlinkage void noinstr el1h_64_fiq_handler(struct pt_regs *regs)
> > +asmlinkage void noinstr el1h_64_irq_handler(struct pt_regs *regs)
> > +{
> > +       if (on_thread_stack())
> > +               call_on_irq_stack(regs, el1_irq);
>
> IMO, this can't work. Because el1_interrupt() will invoke
> arm64_preempt_schedule_irq(), which will cause scheduling on the
> IRQ stack.

Ah, too bad. I spent some more time looking for a simpler approach,
but couldn't find one I'm happy with. One idea might be to have
callback functions for each combinations of irq/fiq with irq/pnmi
to avoid the nested callback pointers. Not sure if that helps.

       Arnd

WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@arndb.de>
To: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Catalin Marinas <catalin.marinas@arm.com>,
	 Will Deacon <will@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	 Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 2/2] arm64: support HAVE_IRQ_EXIT_ON_IRQ_STACK
Date: Thu, 7 Jul 2022 22:55:45 +0200	[thread overview]
Message-ID: <CAK8P3a1GgnmhHj+_gRYZ52=TvfBQb_xxYt1Hg-jMJ2gZqCD42w@mail.gmail.com> (raw)
In-Reply-To: <33a63e76-fb71-2b9e-3b3c-cc6f7a675cf3@bytedance.com>

On Thu, Jul 7, 2022 at 5:00 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote:
> On 2022/7/7 22:41, Arnd Bergmann wrote:
> > On Thu, Jul 7, 2022 at 3:38 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote:
> >> On 2022/7/7 20:49, Arnd Bergmann wrote:
> >
> > -asmlinkage void noinstr el1h_64_fiq_handler(struct pt_regs *regs)
> > +asmlinkage void noinstr el1h_64_irq_handler(struct pt_regs *regs)
> > +{
> > +       if (on_thread_stack())
> > +               call_on_irq_stack(regs, el1_irq);
>
> IMO, this can't work. Because el1_interrupt() will invoke
> arm64_preempt_schedule_irq(), which will cause scheduling on the
> IRQ stack.

Ah, too bad. I spent some more time looking for a simpler approach,
but couldn't find one I'm happy with. One idea might be to have
callback functions for each combinations of irq/fiq with irq/pnmi
to avoid the nested callback pointers. Not sure if that helps.

       Arnd

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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2022-07-07 20:56 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-07 11:05 [RFC PATCH 0/2] arm64: run softirqs on the per-CPU IRQ stack Qi Zheng
2022-07-07 11:05 ` Qi Zheng
2022-07-07 11:05 ` [RFC PATCH 1/2] " Qi Zheng
2022-07-07 11:05   ` Qi Zheng
2022-07-07 12:58   ` Arnd Bergmann
2022-07-07 12:58     ` Arnd Bergmann
2022-07-07 13:43     ` Qi Zheng
2022-07-07 13:43       ` Qi Zheng
2022-07-07 13:53       ` Arnd Bergmann
2022-07-07 13:53         ` Arnd Bergmann
2022-07-07 15:05         ` Qi Zheng
2022-07-07 15:05           ` Qi Zheng
2022-07-08  2:56   ` kernel test robot
2022-07-07 11:05 ` [RFC PATCH 2/2] arm64: support HAVE_IRQ_EXIT_ON_IRQ_STACK Qi Zheng
2022-07-07 11:05   ` Qi Zheng
2022-07-07 12:49   ` Arnd Bergmann
2022-07-07 12:49     ` Arnd Bergmann
2022-07-07 13:38     ` Qi Zheng
2022-07-07 13:38       ` Qi Zheng
2022-07-07 14:41       ` Arnd Bergmann
2022-07-07 14:41         ` Arnd Bergmann
2022-07-07 15:00         ` Qi Zheng
2022-07-07 15:00           ` Qi Zheng
2022-07-07 20:55           ` Arnd Bergmann [this message]
2022-07-07 20:55             ` Arnd Bergmann
2022-07-08  3:13             ` Qi Zheng
2022-07-08  3:13               ` Qi Zheng
2022-07-08  8:52               ` Arnd Bergmann
2022-07-08  8:52                 ` Arnd Bergmann
2022-07-08  9:13                 ` Qi Zheng
2022-07-08  9:13                   ` Qi Zheng

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