From: Preeti U Murthy <preeti@linux•vnet.ibm.com>
To: Benjamin Herrenschmidt <benh@kernel•crashing.org>
Cc: paulmck@linux•vnet.ibm.com, paulus@samba•org,
Anton Blanchard <anton@samba•org>,
linuxppc-dev@lists•ozlabs.org
Subject: Re: [PATCH] powerpc: irq work racing with timer interrupt can result in timer interrupt hang
Date: Sun, 11 May 2014 14:37:33 +0530 [thread overview]
Message-ID: <536F3DD5.8070503@linux.vnet.ibm.com> (raw)
In-Reply-To: <1399799008.17624.43.camel@pasglop>
On 05/11/2014 02:33 PM, Benjamin Herrenschmidt wrote:
> On Sun, 2014-05-11 at 14:13 +0530, Preeti U Murthy wrote:
>>
>> Isn't this patch required too?
>>
>> @@ -503,12 +503,13 @@ void __timer_interrupt(void)
>> now = *next_tb - now;
>> if (now <= DECREMENTER_MAX)
>> set_dec((int)now);
>> - /* We may have raced with new irq work */
>> - if (test_irq_work_pending())
>> - set_dec(1);
>> __get_cpu_var(irq_stat).timer_irqs_others++;
>> }
>>
>> + /* We may have raced with new irq work */
>> + if (test_irq_work_pending())
>> + set_dec(1);
>> +
>>
>> The event_handler cannot be relied upon to call
>> decrementer_set_next_event() all the time. This is in the case where
>> there are no pending timers. In that case we need to have the check on
>> irq work pending at the end of __timer_interrupt() no?
>
> I don't think we need to move the test no. If there's a pending
> irq_work, at that point, it will have done set_dec when being queued up.
> So we only care about cases where we might change the decrementer.
>
> If the event handler doesn't call decrementer_set_next_event() then
> nothing will modify the decrementer and it will still trigger soon.
Hmm ok. Then Anton's patch covers all cases :)
Thanks!
Reviewed-by: Preeti U Murthy <preeti@linux•vnet.ibm.com>
Regards
Preeti U Murthy
>
> Cheers,
> Ben.
>
>
next prev parent reply other threads:[~2014-05-11 9:11 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-09 7:47 [PATCH] powerpc: irq work racing with timer interrupt can result in timer interrupt hang Anton Blanchard
2014-05-09 9:52 ` Preeti U Murthy
2014-05-10 4:26 ` Benjamin Herrenschmidt
2014-05-10 15:36 ` Preeti U Murthy
2014-05-10 22:25 ` Benjamin Herrenschmidt
2014-05-11 8:15 ` Preeti U Murthy
2014-05-11 8:37 ` Benjamin Herrenschmidt
2014-05-11 8:43 ` Preeti U Murthy
2014-05-11 9:03 ` Benjamin Herrenschmidt
2014-05-11 9:07 ` Preeti U Murthy [this message]
2014-05-09 13:41 ` Paul E. McKenney
2014-05-09 21:50 ` Gabriel Paubert
2014-05-09 22:08 ` Paul E. McKenney
2014-05-10 6:33 ` Paul Mackerras
2014-05-10 16:33 ` Paul E. McKenney
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