* [PATCH] powerpc: Fix WARN_ON in decrementer_check_overflow
@ 2012-02-09 5:34 Benjamin Herrenschmidt
2012-02-09 22:25 ` Hugh Dickins
0 siblings, 1 reply; 3+ messages in thread
From: Benjamin Herrenschmidt @ 2012-02-09 5:34 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Hugh Dickins
We use __get_cpu_var() which triggers a false positive warning
in smp_processor_id() thinking interrupts are enabled (at this
point, they are soft-enabled but hard-disabled).
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
I was initially planning to fix that with a more in-depth rework
of how we do lazy irq disabling on powerpc, but that patch is
becoming too complex for this release so I'll apply this as a
stop-gap and leave the full rework for -next
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 701d4ac..01e2877 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -118,10 +118,14 @@ static inline notrace void set_soft_enabled(unsigned long enable)
static inline notrace void decrementer_check_overflow(void)
{
u64 now = get_tb_or_rtc();
- u64 *next_tb = &__get_cpu_var(decrementers_next_tb);
+ u64 *next_tb;
+
+ preempt_disable();
+ next_tb = &__get_cpu_var(decrementers_next_tb);
if (now >= *next_tb)
set_dec(1);
+ preempt_enable();
}
notrace void arch_local_irq_restore(unsigned long en)
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] powerpc: Fix WARN_ON in decrementer_check_overflow
2012-02-09 5:34 [PATCH] powerpc: Fix WARN_ON in decrementer_check_overflow Benjamin Herrenschmidt
@ 2012-02-09 22:25 ` Hugh Dickins
2012-02-09 22:45 ` Benjamin Herrenschmidt
0 siblings, 1 reply; 3+ messages in thread
From: Hugh Dickins @ 2012-02-09 22:25 UTC (permalink / raw)
To: Benjamin Herrenschmidt; +Cc: linuxppc-dev
On Thu, 9 Feb 2012, Benjamin Herrenschmidt wrote:
> We use __get_cpu_var() which triggers a false positive warning
> in smp_processor_id() thinking interrupts are enabled (at this
> point, they are soft-enabled but hard-disabled).
>
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> ---
>
> I was initially planning to fix that with a more in-depth rework
> of how we do lazy irq disabling on powerpc, but that patch is
> becoming too complex for this release so I'll apply this as a
> stop-gap and leave the full rework for -next
Okay, thanks for the update, that's equivalent to the get_cpu_var
plus put_cpu_var patch I had generally been running with successfully.
(I was not at all confident that it was a sufficient fix, and have
to say "generally" above because one time I got something that looked
like recursive calls overflowing the stack, and IIRC something "irq"
did appear in each frame of the trace. But probably no connection,
never seen again, and I don't recall even which -rc or -next it was.)
Hugh
>
> diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
> index 701d4ac..01e2877 100644
> --- a/arch/powerpc/kernel/irq.c
> +++ b/arch/powerpc/kernel/irq.c
> @@ -118,10 +118,14 @@ static inline notrace void set_soft_enabled(unsigned long enable)
> static inline notrace void decrementer_check_overflow(void)
> {
> u64 now = get_tb_or_rtc();
> - u64 *next_tb = &__get_cpu_var(decrementers_next_tb);
> + u64 *next_tb;
> +
> + preempt_disable();
> + next_tb = &__get_cpu_var(decrementers_next_tb);
>
> if (now >= *next_tb)
> set_dec(1);
> + preempt_enable();
> }
>
> notrace void arch_local_irq_restore(unsigned long en)
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] powerpc: Fix WARN_ON in decrementer_check_overflow
2012-02-09 22:25 ` Hugh Dickins
@ 2012-02-09 22:45 ` Benjamin Herrenschmidt
0 siblings, 0 replies; 3+ messages in thread
From: Benjamin Herrenschmidt @ 2012-02-09 22:45 UTC (permalink / raw)
To: Hugh Dickins; +Cc: linuxppc-dev
On Thu, 2012-02-09 at 14:25 -0800, Hugh Dickins wrote:
>
> Okay, thanks for the update, that's equivalent to the get_cpu_var
> plus put_cpu_var patch I had generally been running with successfully.
>
> (I was not at all confident that it was a sufficient fix, and have
> to say "generally" above because one time I got something that looked
> like recursive calls overflowing the stack, and IIRC something "irq"
> did appear in each frame of the trace. But probably no connection,
> never seen again, and I don't recall even which -rc or -next it was.)
If you ever see that again, please shoot me the log !
Cheers,
Ben.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-02-09 5:34 [PATCH] powerpc: Fix WARN_ON in decrementer_check_overflow Benjamin Herrenschmidt
2012-02-09 22:25 ` Hugh Dickins
2012-02-09 22:45 ` Benjamin Herrenschmidt
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