linux-kernel - Re: [PATCH] x86/apic: Fix suspicious RCU usage in smp_trace_call_function

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Message-ID: <CANRm+Cx4g=_BSB23Dk7TcWGGfGVcNtOWHmA+6+=+BX2JRAkaRw@mail.gmail.com>
Date:   Sun, 18 Sep 2016 16:32:53 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Wanpeng Li <wanpeng.li@...mail.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] x86/apic: Fix suspicious RCU usage in smp_trace_call_function_interrupt

2016-09-15 16:58 GMT+08:00 Thomas Gleixner <tglx@...utronix.de>:
> On Thu, 15 Sep 2016, Wanpeng Li wrote:
>> ---
>>  arch/x86/include/asm/apic.h | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
>> index 1243577..71c1fe2 100644
>> --- a/arch/x86/include/asm/apic.h
>> +++ b/arch/x86/include/asm/apic.h
>> @@ -650,8 +650,8 @@ static inline void entering_ack_irq(void)
>>
>>  static inline void ipi_entering_ack_irq(void)
>>  {
>> -     ack_APIC_irq();
>>       irq_enter();
>> +     ack_APIC_irq();
>>  }
>
> which makes ipi_entering_ack_irq() the same as entering_ack_irq() and
> therefor pointless.
>
> Looking further we have the same issue in exiting_ack_irq() where we call
> ack_APIC_irq() after irq_exit().

Do you think I should fix both ipi_entering_ack_irq() and exiting_ack_irq()?

Regards,
Wanpeng Li