Commit 7c0482e3 authored by Benjamin Herrenschmidt's avatar Benjamin Herrenschmidt
Browse files

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



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: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 4e25651b

arch/powerpc/kernel/entry_64.S

+31 −13
Original line number Diff line number Diff line
@@ -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? */

arch/powerpc/kernel/irq.c

+13 −0
Original line number Diff line number Diff line
@@ -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);



	/*

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