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Subject[ 009/187] powerpc: check_and_cede_processor() never cedes
Date
From: Greg KH <gregkh@linuxfoundation.org>

3.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Anton Blanchard <anton@samba.org>

commit 0b17ba7258db83cd02da560884e053b85de371f2 upstream.

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
nothing.

This issue will eventually appear in 3.4 stable since the
hard_irq_disable fix is marked stable, so mark this one for stable
too.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/powerpc/include/asm/hw_irq.h | 5 +++++
arch/powerpc/platforms/pseries/processor_idle.c | 2 +-
2 files changed, 6 insertions(+), 1 deletion(-)

--- a/arch/powerpc/include/asm/hw_irq.h
+++ b/arch/powerpc/include/asm/hw_irq.h
@@ -102,6 +102,11 @@ 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
--- a/arch/powerpc/platforms/pseries/processor_idle.c
+++ b/arch/powerpc/platforms/pseries/processor_idle.c
@@ -106,7 +106,7 @@ static void check_and_cede_processor(voi
* we first hard disable then check.
*/
hard_irq_disable();
- if (get_paca()->irq_happened == 0)
+ if (!lazy_irq_pending())
cede_processor();
}




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