On 07/06/2013 11:15 AM, Wang YanQing wrote:
> On Fri, Jul 05, 2013 at 09:57:21PM +0530, Preeti U Murthy wrote:
>> call_single_data is always locked by all callers of
>> arch_send_call_function_single_ipi() or
>> arch_send_call_function_ipi_mask() which results in execution of
>> generic_call_function_interrupt() handler.
>>
>> Hence remove the check for lock on csd in generic_call_function_interrupt()
>> handler, before unlocking it.
>
> I can't find where is the generic_call_function_interrupt :)
Sorry about this error :)
>
>> Signed-off-by: Preeti U Murthy <pre...@linux.vnet.ibm.com>
>> Cc: Peter Zijlstra <a.p.zijls...@chello.nl>
>> Cc: Ingo Molnar <mi...@elte.hu>
>> Cc: Xiao Guangrong <xiaoguangr...@cn.fujitsu.com>
>> Cc: srivatsa.b...@linux.vnet.ibm.com
>> Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com>
>> Cc: Steven Rostedt <rost...@goodmis.org>
>> Cc: Rusty Russell <ru...@rustcorp.com.au
>> ---
>>
>> kernel/smp.c | 14 +-------------
>> 1 file changed, 1 insertion(+), 13 deletions(-)
>>
>> diff --git a/kernel/smp.c b/kernel/smp.c
>> index b6981ae..d37581a 100644
>> --- a/kernel/smp.c
>> +++ b/kernel/smp.c
>> @@ -181,25 +181,13 @@ void generic_smp_call_function_single_interrupt(void)
>>
>> while (!list_empty(&list)) {
>> struct call_single_data *csd;
>> - unsigned int csd_flags;
>>
>> csd = list_entry(list.next, struct call_single_data, list);
>> list_del(&csd->list);
>>
>> - /*
>> - * 'csd' can be invalid after this call if flags == 0
>> - * (when called through generic_exec_single()),
>> - * so save them away before making the call:
>> - */
>> - csd_flags = csd->flags;
>> -
>
> You haven't mention this change in the ChangeLog, don't do it.
Right, I will include it in the changelog.
> I can't see any harm to remove csd_flags, but I hope others
> check it again.
>
>> csd->func(csd->info);
>>
>> - /*
>> - * Unlocked CSDs are valid through generic_exec_single():
>> - */
>> - if (csd_flags & CSD_FLAG_LOCK)
>> - csd_unlock(csd);
>> + csd_unlock(csd);
>
> I don't like this change, I think check CSD_FLAG_LOCK
> to make sure we really need csd_unlock is good.
Ideally it should be under a WARN_ON(). csd_unlock() has that WARN_ON().
Unlocking a parameter which is not locked should be seen as a bug, which
the above code is not doing. In fact it avoids it being reported as a bug.
>
> Just like you can't know who and how people will use the
> API, so some robust check code is good.
>
Regards
Preeti U Murthy
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
