[PATCH] powerpc: check_and_cede_processor never cedes
anton at samba.org
Thu Jun 28 09:13:52 EST 2012
> I'd rather add a helper, something like lazy_irq_pending()
> and hide the actual check for the bits in irq_happened, in
> case we change the scheme again.
Good idea. Look ok?
Commit f948501b36c6 ("Make hard_irq_disable() actually hard-disable
interrupts") caused check_and_cede_processor to stop working.
->irq_happened will never be zero right after a hard_irq_disable
so the compiler removes the call to cede_processor completely.
The bug was introduced back in the lazy interrupt handling rework
of 3.4 but was hidden until recently because hard_irq_disable did
This issue will eventually appear in 3.4 stable since the
hard_irq_disable fix is marked stable, so mark this one for stable
Signed-off-by: Anton Blanchard <anton at samba.org>
Cc: stable at vger.kernel.org
v2: create a helper, suggested by Ben.
--- linux-build.orig/arch/powerpc/platforms/pseries/processor_idle.c 2012-06-28 08:55:09.422198154 +1000
+++ linux-build/arch/powerpc/platforms/pseries/processor_idle.c 2012-06-28 08:57:36.112591023 +1000
@@ -106,7 +106,7 @@ static void check_and_cede_processor(voi
* we first hard disable then check.
- if (get_paca()->irq_happened == 0)
+ if (!lazy_irq_pending())
--- linux-build.orig/arch/powerpc/include/asm/hw_irq.h 2012-06-21 09:16:26.265354429 +1000
+++ linux-build/arch/powerpc/include/asm/hw_irq.h 2012-06-28 08:59:22.082320381 +1000
@@ -103,6 +103,11 @@ static inline void hard_irq_disable(void
/* include/linux/interrupt.h needs hard_irq_disable to be a macro */
#define hard_irq_disable hard_irq_disable
+static inline bool lazy_irq_pending(void)
+ return !!(get_paca()->irq_happened & ~PACA_IRQ_HARD_DIS);
* This is called by asynchronous interrupts to conditionally
* re-enable hard interrupts when soft-disabled after having
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