From: Benjamin Herrenschmidt <benh@kernel•crashing.org>
To: Preeti U Murthy <preeti@linux•vnet.ibm.com>
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: Sat, 10 May 2014 14:26:33 +1000 [thread overview]
Message-ID: <1399695993.4481.47.camel@pasglop> (raw)
In-Reply-To: <536CA561.8010803@linux.vnet.ibm.com>
On Fri, 2014-05-09 at 15:22 +0530, Preeti U Murthy wrote:
> in __timer_interrupt() outside the _else_ loop? This will ensure that no
> matter what, before exiting timer interrupt handler we check for pending
> irq work.
We still need to make sure that set_next_event() doesn't move the
dec beyond the next tick if there is a pending timer... maybe we
can fix it like this:
static int decrementer_set_next_event(unsigned long evt,
struct clock_event_device *dev)
{
__get_cpu_var(decrementers_next_tb) = get_tb_or_rtc() + evt;
/* Don't adjust the decrementer if some irq work is pending */
if (!test_irq_work_pending())
set_dec(evt);
return 0;
}
Along with a single occurrence of:
if (test_irq_work_pending())
set_dec(1);
At the end of __timer_interrupt(), outside if the current else {}
case, this should work, don't you think ?
What about this completely untested patch ?
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 122a580..ba7e83b 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -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);
+
#ifdef CONFIG_PPC64
/* collect purr register values often, for accurate calculations */
if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
@@ -813,15 +814,11 @@ static void __init clocksource_init(void)
static int decrementer_set_next_event(unsigned long evt,
struct clock_event_device *dev)
{
- /* Don't adjust the decrementer if some irq work is pending */
- if (test_irq_work_pending())
- return 0;
__get_cpu_var(decrementers_next_tb) = get_tb_or_rtc() + evt;
- set_dec(evt);
- /* We may have raced with new irq work */
- if (test_irq_work_pending())
- set_dec(1);
+ /* Don't adjust the decrementer if some irq work is pending */
+ if (!test_irq_work_pending())
+ set_dec(evt);
return 0;
}
next prev parent reply other threads:[~2014-05-10 4:26 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 [this message]
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
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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