linux-kernel - Re: [PATCH v1 1/2] arm64: run softirqs on the per-CPU IRQ stack

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Date:   Fri, 22 Jul 2022 17:13:39 +0800
From:   Qi Zheng <zhengqi.arch@...edance.com>
To:     Will Deacon <will@...nel.org>
Cc:     arnd@...db.de, catalin.marinas@....com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/2] arm64: run softirqs on the per-CPU IRQ stack



On 2022/7/22 17:04, Will Deacon wrote:
> On Fri, Jul 08, 2022 at 05:49:49PM +0800, 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@...edance.com>
>> ---
>>   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 4c1e1d2d2f8b..be0a9f0052ee 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
> 
> Acked-by: Will Deacon <will@...nel.org>
> 
> Please can you repost this at -rc1 and we can queue it up for 5.21?

Sure, will do.

Thanks,
Qi

> 
> Thanks,
> 
> Will

-- 
Thanks,
Qi