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Message-ID: <430e3e5f-d446-6307-cba0-6f859bce560f@bytedance.com>
Date:   Wed, 7 Sep 2022 15:04:48 +0800
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Subject: Re: [PATCH v3] arm64: run softirqs on the per-CPU IRQ stack
Content-Language: en-US
From:   Qi Zheng <zhengqi.arch@bytedance.com>
To:     will@kernel.org
Cc:     linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Arnd Bergmann <arnd@arndb.de>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Mark Rutland <mark.rutland@arm.com>
References: <20220815124739.15948-1-zhengqi.arch@bytedance.com>
 <595c912a-1503-d420-f32f-297b824decae@bytedance.com>
In-Reply-To: <595c912a-1503-d420-f32f-297b824decae@bytedance.com>
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On 2022/8/26 12:16, Qi Zheng wrote:
> 
> 
> On 2022/8/15 20:47, Qi Zheng wrote:
>> Currently arm64 supports per-CPU IRQ stack, but softirqs
>> are still handled in the task context.
>>
>> Since any call to local_bh_enable() at any level in the task's
>> call stack may trigger a softirq processing run, which could
>> potentially cause a task stack overflow if the combined stack
>> footprints exceed the stack's size, let's run these softirqs
>> on the IRQ stack as well.
>>
>> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
>> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
>> Acked-by: Will Deacon <will@kernel.org>
>> ---
>> v2: 
>> https://lore.kernel.org/lkml/20220802065325.39740-1-zhengqi.arch@bytedance.com/
>> v1: 
>> https://lore.kernel.org/lkml/20220708094950.41944-1-zhengqi.arch@bytedance.com/
>> RFC: 
>> https://lore.kernel.org/lkml/20220707110511.52129-1-zhengqi.arch@bytedance.com/
>>
>> Changelog in v2 -> v3:
>>   - rebase onto the v6.0-rc1

Hi Will,

Are we good to merge this patch? Or if there is anything else I need to
do, please let me know. :)

Looking forward to your reply.

Thanks,
Qi

> 
> Gentle ping.
> 
> Thanks,
> Qi
> 
>>
>> Changelog in v1 -> v2:
>>   - temporarily discard [PATCH v1 2/2] to allow this patch to be 
>> merged first
>>   - rebase onto the v5.19
>>   - collect Reviewed-by and Acked-by
>>
>> Changelog in RFC -> v1:
>>   - fix conflicts with commit f2c5092190f2 ("arch/*: Disable softirq 
>> stacks on PREEMPT_RT.")
>>
>>   arch/arm64/Kconfig      |  1 +
>>   arch/arm64/kernel/irq.c | 13 +++++++++++++
>>   2 files changed, 14 insertions(+)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 571cc234d0b3..ee92f5887cf6 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -230,6 +230,7 @@ config ARM64
>>       select HAVE_ARCH_USERFAULTFD_MINOR if USERFAULTFD
>>       select TRACE_IRQFLAGS_SUPPORT
>>       select TRACE_IRQFLAGS_NMI_SUPPORT
>> +    select HAVE_SOFTIRQ_ON_OWN_STACK
>>       help
>>         ARM 64-bit (AArch64) Linux support.
>> diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c
>> index bda49430c9ea..c36ad20a52f3 100644
>> --- a/arch/arm64/kernel/irq.c
>> +++ b/arch/arm64/kernel/irq.c
>> @@ -22,6 +22,7 @@
>>   #include <linux/vmalloc.h>
>>   #include <asm/daifflags.h>
>>   #include <asm/vmap_stack.h>
>> +#include <asm/exception.h>
>>   /* Only access this in an NMI enter/exit */
>>   DEFINE_PER_CPU(struct nmi_ctx, nmi_contexts);
>> @@ -71,6 +72,18 @@ static void init_irq_stacks(void)
>>   }
>>   #endif
>> +#ifndef CONFIG_PREEMPT_RT
>> +static void ____do_softirq(struct pt_regs *regs)
>> +{
>> +    __do_softirq();
>> +}
>> +
>> +void do_softirq_own_stack(void)
>> +{
>> +    call_on_irq_stack(NULL, ____do_softirq);
>> +}
>> +#endif
>> +
>>   static void default_handle_irq(struct pt_regs *regs)
>>   {
>>       panic("IRQ taken without a root IRQ handler\n");
> 

-- 
Thanks,
Qi