Re: [PATCH] Fix: membarrier: add missing preempt off around smp_call_function_many

[Mathieu Desnoyers]

Hi Linus,

Can you pick up this straightforward fix please ? Let me know whether
I need to re-send the patch if for some reason the original post is
too far back in your inbox.

Thanks,

Mathieu

----- On Dec 20, 2017, at 10:02 AM, Mathieu Desnoyers mathieu.desnoyers@xxxxxxxxxxxx wrote:

> Hi Linus, Peter, Ingo,
> 
> Now that membarrier.c has been moved from kernel/ to kernel/sched/, should
> I route this membarrier fix through the scheduler maintainers, or is it OK
> to send it to you directly ?
> 
> Thanks,
> 
> Mathieu
> 
> ----- On Dec 15, 2017, at 2:23 PM, Mathieu Desnoyers
> mathieu.desnoyers@xxxxxxxxxxxx wrote:
> 
>> smp_call_function_many requires disabling preemption around the call.
>> 
>> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
>> CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
>> CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
>> CC: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
>> CC: Boqun Feng <boqun.feng@xxxxxxxxx>
>> CC: Andrew Hunter <ahh@xxxxxxxxxx>
>> CC: Maged Michael <maged.michael@xxxxxxxxx>
>> CC: Avi Kivity <avi@xxxxxxxxxxxx>
>> CC: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
>> CC: Paul Mackerras <paulus@xxxxxxxxx>
>> CC: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
>> CC: Dave Watson <davejwatson@xxxxxx>
>> CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
>> CC: Ingo Molnar <mingo@xxxxxxxxxx>
>> CC: "H. Peter Anvin" <hpa@xxxxxxxxx>
>> CC: Andrea Parri <parri.andrea@xxxxxxxxx>
>> CC: <stable@xxxxxxxxxxxxxxx>	# v4.14
>> ---
>> kernel/sched/membarrier.c | 2 ++
>> 1 file changed, 2 insertions(+)
>> 
>> diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
>> index dd7908743dab..9bcbacba82a8 100644
>> --- a/kernel/sched/membarrier.c
>> +++ b/kernel/sched/membarrier.c
>> @@ -89,7 +89,9 @@ static int membarrier_private_expedited(void)
>> 		rcu_read_unlock();
>> 	}
>> 	if (!fallback) {
>> +		preempt_disable();
>> 		smp_call_function_many(tmpmask, ipi_mb, NULL, 1);
>> +		preempt_enable();
>> 		free_cpumask_var(tmpmask);
>> 	}
>> 	cpus_read_unlock();
>> --
>> 2.11.0
> 
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com