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
WARNING: multiple messages have this Message-ID (diff)
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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-07-08 9:13 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 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 [this message] 2022-07-08 9:13 ` Qi Zheng
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