linux-kernel - Re: [PATCH v3 13/16] powerpc/watchpoint: Prepare handler to handle more than one watcnhpoint

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Message-ID: <f571127c-89b0-a333-be71-18f411dc6586@linux.ibm.com>
Date:   Fri, 24 Apr 2020 09:02:12 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     mpe@...erman.id.au, mikey@...ling.org, apopple@...ux.ibm.com,
        paulus@...ba.org, npiggin@...il.com,
        naveen.n.rao@...ux.vnet.ibm.com, peterz@...radead.org,
        jolsa@...nel.org, oleg@...hat.com, fweisbec@...il.com,
        mingo@...nel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Subject: Re: [PATCH v3 13/16] powerpc/watchpoint: Prepare handler to handle
 more than one watcnhpoint

Hi Christophe,

>> @@ -101,14 +129,20 @@ static bool is_ptrace_bp(struct perf_event *bp)
>>    */
>>   void arch_unregister_hw_breakpoint(struct perf_event *bp)
>>   {
>> +    int i;
>> +
> 
> This declaration should be in the block using it.
> 
>>       /*
>>        * If the breakpoint is unregistered between a hw_breakpoint_handler()
>>        * and the single_step_dabr_instruction(), then cleanup the breakpoint
>>        * restoration variables to prevent dangling pointers.
>>        * FIXME, this should not be using bp->ctx at all! Sayeth peterz.
>>        */
>> -    if (bp->ctx && bp->ctx->task && bp->ctx->task != ((void *)-1L))
>> -        bp->ctx->task->thread.last_hit_ubp = NULL;
>> +    if (bp->ctx && bp->ctx->task && bp->ctx->task != ((void *)-1L)) {
> 
> Add declaration of 'int i' here.

How will that help? Keeping declaration at the start of function is also
common practice and I don't see any recommendation to move them inside
conditional block.

Thanks,
Ravi