From: Nicholas Piggin <npiggin@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>,
Nicholas Piggin <npiggin@gmail.com>
Subject: [PATCH 1/3] powerpc/64s/interrupt: Fix decrementer storm
Date: Tue, 25 Jan 2022 00:39:28 +1000 [thread overview]
Message-ID: <20220124143930.3923442-1-npiggin@gmail.com> (raw)
The decrementer exception can fail to be cleared when the interrupt
returns in the case where the decrementer wraps with the next timer
still beyond decrementer_max. This results in a decrementer interrupt
storm. This is triggerable with small decrementer system with hard
and soft watchdogs disabled.
Fix this by always programming the decrementer if there was no timer.
Fixes: 0faf20a1ad16 ("powerpc/64s/interrupt: Don't enable MSR[EE] in irq handlers unless perf is in use")
Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
arch/powerpc/kernel/time.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 62361cc7281c..cd0b8b71ecdd 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -649,8 +649,9 @@ DEFINE_INTERRUPT_HANDLER_ASYNC(timer_interrupt)
__this_cpu_inc(irq_stat.timer_irqs_event);
} else {
now = *next_tb - now;
- if (now <= decrementer_max)
- set_dec_or_work(now);
+ if (now > decrementer_max)
+ now = decrementer_max;
+ set_dec_or_work(now);
__this_cpu_inc(irq_stat.timer_irqs_others);
}
--
2.23.0
next reply other threads:[~2022-01-24 14:40 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-24 14:39 Nicholas Piggin [this message]
2022-01-24 14:39 ` [PATCH 2/3] powerpc/time: Fix KVM host re-arming a timer beyond decrementer range Nicholas Piggin
2022-01-24 14:39 ` [PATCH 3/3] powerpc/time: improve decrementer clockevent processing Nicholas Piggin
2022-01-29 11:14 ` (subset) [PATCH 1/3] powerpc/64s/interrupt: Fix decrementer storm Michael Ellerman
2022-03-21 5:05 ` Michael Ellerman
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