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Commit 4f917ba3 authored by Benjamin Herrenschmidt's avatar Benjamin Herrenschmidt
Browse files

powerpc/ppc64: Use preempt_schedule_irq instead of preempt_schedule 



Based on an original patch by Valentine Barshak <vbarshak@ru.mvista.com>

Use preempt_schedule_irq to prevent infinite irq-entry and
eventual stack overflow problems with fast-paced IRQ sources.

This kind of problems has been observed on the PASemi Electra IDE
controller. We have to make sure we are soft-disabled before calling
preempt_schedule_irq and hard disable interrupts after that
to avoid unrecoverable exceptions.

This patch also moves the "clrrdi r9,r1,THREAD_SHIFT" out of
the #ifdef CONFIG_PPC_BOOK3E scope, since r9 is clobbered
and has to be restored in both cases.

Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 01deab98

arch/powerpc/kernel/entry_64.S

+21 −20
Original line number Diff line number Diff line
@@ -658,42 +658,43 @@ do_work: 
	cmpdi	r0,0

	crandc	eq,cr1*4+eq,eq

	bne	restore

	/* here we are preempting the current task */

1:

#ifdef CONFIG_TRACE_IRQFLAGS

	bl	.trace_hardirqs_on

	/* Note: we just clobbered r10 which used to contain the previous

	 * MSR before the hard-disabling done by the caller of do_work.

	 * We don't have that value anymore, but it doesn't matter as

	 * we will hard-enable unconditionally, we can just reload the

	 * current MSR into r10



	/* Here we are preempting the current task.

	 *

	 * Ensure interrupts are soft-disabled. We also properly mark

	 * the PACA to reflect the fact that they are hard-disabled

	 * and trace the change

	 */

	mfmsr	r10

#endif /* CONFIG_TRACE_IRQFLAGS */

	li	r0,1

	li	r0,0

	stb	r0,PACASOFTIRQEN(r13)

	stb	r0,PACAHARDIRQEN(r13)

	TRACE_DISABLE_INTS



	/* Call the scheduler with soft IRQs off */

1:	bl	.preempt_schedule_irq



	/* Hard-disable interrupts again (and update PACA) */

#ifdef CONFIG_PPC_BOOK3E

	wrteei	1

	bl	.preempt_schedule

	wrteei	0

#else

	ori	r10,r10,MSR_EE

	mtmsrd	r10,1		/* reenable interrupts */

	bl	.preempt_schedule

	mfmsr	r10

	clrrdi	r9,r1,THREAD_SHIFT

	rldicl	r10,r10,48,1	/* disable interrupts again */

	rldicl	r10,r10,48,1

	rotldi	r10,r10,16

	mtmsrd	r10,1

#endif /* CONFIG_PPC_BOOK3E */

	li	r0,0

	stb	r0,PACAHARDIRQEN(r13)



	/* Re-test flags and eventually loop */

	clrrdi	r9,r1,THREAD_SHIFT

	ld	r4,TI_FLAGS(r9)

	andi.	r0,r4,_TIF_NEED_RESCHED

	bne	1b

	b	restore



user_work:

#endif

#endif /* CONFIG_PREEMPT */



	/* Enable interrupts */

#ifdef CONFIG_PPC_BOOK3E

	wrteei	1