The following commit has been merged in the linux branch: commit 4f917ba3d5ee9c98d60fa357e799942df8412de3 Author: Benjamin Herrenschmidt benh@kernel.crashing.org Date: Mon Oct 26 19:41:17 2009 +0000
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: Benjamin Herrenschmidt benh@kernel.crashing.org
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index f9fd54b..9763267 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -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