From: Qi Zheng <zhengqi.arch@bytedance.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: 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: Fri, 8 Jul 2022 17:13:40 +0800 [thread overview]
Message-ID: <548be593-2849-a05b-7fef-66605d41bf5c@bytedance.com> (raw)
In-Reply-To: <CAK8P3a3DDEkr0D=dLiXN+Xek_OO-HX5xWaQpzdX1GQxTYWnHLw@mail.gmail.com>
On 2022/7/8 16:52, Arnd Bergmann wrote:
> On Fri, Jul 8, 2022 at 5:13 AM Qi Zheng <zhengqi.arch@bytedance.com> wrote:
>> On 2022/7/8 04:55, Arnd Bergmann wrote:
>>> 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.
>>
>> Maybe nested callback pointers are not always a wild beast. ;)
>> This method does not change much, and we can also conveniently stuff
>> all kinds of things in do_handler() that we want to run on the IRQ
>> stack in addition to the handler().
>
> Right, your approach is probably the one that changes the existing
> code the least. I see that x86 handles this by having call_on_irq_stack()
> in an inline asm, but this in turn complicates the asm implementation,
> which is also worth keeping simple.
Yes, and I see that the commit f2c5092190f2 ("arch/*: Disable softirq
stacks on PREEMPT_RT.") has been merged into next-20220707, so I will
rebase to the next-20220707 and send the next version.
Thank you very much :)
>
> Arnd
--
Thanks,
Qi
prev parent reply other threads:[~2022-07-08 9:13 UTC|newest]
Thread overview: 15+ 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 ` [RFC PATCH 1/2] " Qi Zheng
2022-07-07 12:58 ` Arnd Bergmann
2022-07-07 13:43 ` Qi Zheng
2022-07-07 13:53 ` Arnd Bergmann
2022-07-07 15:05 ` Qi Zheng
2022-07-07 11:05 ` [RFC PATCH 2/2] arm64: support HAVE_IRQ_EXIT_ON_IRQ_STACK Qi Zheng
2022-07-07 12:49 ` Arnd Bergmann
2022-07-07 13:38 ` Qi Zheng
2022-07-07 14:41 ` Arnd Bergmann
2022-07-07 15:00 ` Qi Zheng
2022-07-07 20:55 ` Arnd Bergmann
2022-07-08 3:13 ` Qi Zheng
2022-07-08 8:52 ` Arnd Bergmann
2022-07-08 9:13 ` Qi Zheng [this message]
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