linux-kernel - Re: [PATCH 08/15] powerpc/watchpoint: Disable all available watchpoints when !dawr_force

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Date:   Wed, 18 Mar 2020 13:02:35 +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 08/15] powerpc/watchpoint: Disable all available
 watchpoints when !dawr_force_enable



On 3/17/20 4:05 PM, Christophe Leroy wrote:
> 
> 
> Le 09/03/2020 à 09:57, Ravi Bangoria a écrit :
>> Instead of disabling only first watchpoint, disable all available
>> watchpoints while clearing dawr_force_enable.
>>
>> Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
>> ---
>>   arch/powerpc/kernel/dawr.c | 10 +++++++---
>>   1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/powerpc/kernel/dawr.c b/arch/powerpc/kernel/dawr.c
>> index 311e51ee09f4..5c882f07ac7d 100644
>> --- a/arch/powerpc/kernel/dawr.c
>> +++ b/arch/powerpc/kernel/dawr.c
>> @@ -50,9 +50,13 @@ int set_dawr(struct arch_hw_breakpoint *brk, int nr)
>>       return 0;
>>   }
>> -static void set_dawr_cb(void *info)
>> +static void disable_dawrs(void *info)
> 
> Can you explain a bit more what you do exactly ? Why do you change the name of the function and why the parameter becomes NULL ? And why it doens't take into account the parameter anymore ?

Before:
   static void set_dawr_cb(void *info)
   {
           set_dawr(info);
   }
   
   static ssize_t dawr_write_file_bool(...)
   {
   	...
           /* If we are clearing, make sure all CPUs have the DAWR cleared */
           if (!dawr_force_enable)
                   smp_call_function(set_dawr_cb, &null_brk, 0);
   }

After:
   static void disable_dawrs(void *info)
   {
           struct arch_hw_breakpoint null_brk = {0};
           int i;
   
           for (i = 0; i < nr_wp_slots(); i++)
                   set_dawr(&null_brk, i);
   }
   
   static ssize_t dawr_write_file_bool(...)
   {
   	...
           /* If we are clearing, make sure all CPUs have the DAWR cleared */
           if (!dawr_force_enable)
                   smp_call_function(disable_dawrs, NULL, 0);
   }

We use callback function only for disabling watchpoint. Thus I renamed
it to disable_dawrs(). And we are passing null_brk as parameter which
is not really required while disabling watchpoint. So removed it.

Thanks,
Ravi