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powerpc/irq: Fix another case of lazy IRQ state getting out of sync

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So we have another case of paca->irq_happened getting out of
sync with the HW irq state. This can happen when a perfmon
interrupt occurs while soft disabled, as it will return to a
soft disabled but hard enabled context while leaving a stale
PACA_IRQ_HARD_DIS flag set.

This patch fixes it, and also adds a test for the condition
of those flags being out of sync in arch_local_irq_restore()
when CONFIG_TRACE_IRQFLAGS is enabled.

This helps catching those gremlins faster (and so far I
can't seem see any anymore, so that's good news).

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Benjamin Herrenschmidt 2012-05-10 16:12:38 +00:00
parent 4e25651b70
commit 7c0482e3d0
2 changed files with 44 additions and 13 deletions
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44
arch/powerpc/kernel/entry_64.S
View File

@ -588,23 +588,19 @@ _GLOBAL(ret_from_except_lite)
fast_exc_return_irq:
restore:
/*
* This is the main kernel exit path, we first check if we
* have to change our interrupt state.
* This is the main kernel exit path. First we check if we
* are about to re-enable interrupts
*/
ld r5,SOFTE(r1)
lbz r6,PACASOFTIRQEN(r13)
cmpwi cr1,r5,0
cmpw cr0,r5,r6
beq cr0,4f
cmpwi cr0,r5,0
beq restore_irq_off
/* We do, handle disable first, which is easy */
bne cr1,3f;
li r0,0
stb r0,PACASOFTIRQEN(r13);
TRACE_DISABLE_INTS
b 4f
/* We are enabling, were we already enabled ? Yes, just return */
cmpwi cr0,r6,1
beq cr0,do_restore
3: /*
/*
* We are about to soft-enable interrupts (we are hard disabled
* at this point). We check if there's anything that needs to
* be replayed first.
@ -626,7 +622,7 @@ restore_no_replay:
/*
* Final return path. BookE is handled in a different file
*/
4:
do_restore:
#ifdef CONFIG_PPC_BOOK3E
b .exception_return_book3e
#else
@ -699,6 +695,25 @@ fast_exception_return:
#endif /* CONFIG_PPC_BOOK3E */
/*
* We are returning to a context with interrupts soft disabled.
*
* However, we may also about to hard enable, so we need to
* make sure that in this case, we also clear PACA_IRQ_HARD_DIS
* or that bit can get out of sync and bad things will happen
*/
restore_irq_off:
ld r3,_MSR(r1)
lbz r7,PACAIRQHAPPENED(r13)
andi. r0,r3,MSR_EE
beq 1f
rlwinm r7,r7,0,~PACA_IRQ_HARD_DIS
stb r7,PACAIRQHAPPENED(r13)
1: li r0,0
stb r0,PACASOFTIRQEN(r13);
TRACE_DISABLE_INTS
b do_restore
/*
* Something did happen, check if a re-emit is needed
* (this also clears paca->irq_happened)
@ -748,6 +763,9 @@ restore_check_irq_replay:
#endif /* CONFIG_PPC_BOOK3E */
1: b .ret_from_except /* What else to do here ? */
3:
do_work:
#ifdef CONFIG_PREEMPT
andi. r0,r3,MSR_PR /* Returning to user mode? */

13
arch/powerpc/kernel/irq.c
View File

@ -229,6 +229,19 @@ notrace void arch_local_irq_restore(unsigned long en)
*/
if (unlikely(irq_happened != PACA_IRQ_HARD_DIS))
__hard_irq_disable();
#ifdef CONFIG_TRACE_IRQFLAG
else {
/*
* We should already be hard disabled here. We had bugs
* where that wasn't the case so let's dbl check it and
* warn if we are wrong. Only do that when IRQ tracing
* is enabled as mfmsr() can be costly.
*/
if (WARN_ON(mfmsr() & MSR_EE))
__hard_irq_disable();
}
#endif /* CONFIG_TRACE_IRQFLAG */
set_soft_enabled(0);
/*