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[POWERPC] Fix PMU + soft interrupt disable bug

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Since the PMU is an NMI now, it can come at any time we are only soft
disabled.  We must hard disable around the two places we allow the kernel
stack SLB and r1 to go out of sync.  Otherwise the PMU exception can
force a kernel stack SLB into another slot, which can lead to it
getting evicted, which can lead to a nasty unrecoverable SLB miss
in the exception entry code.

Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Anton Blanchard 2008-03-17 15:27:09 +11:00 committed by Paul Mackerras
parent c2372eb9bc
commit 44387e9ff2
2 changed files with 12 additions and 0 deletions
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6
arch/powerpc/kernel/process.c
View file

@ -353,6 +353,12 @@ struct task_struct *__switch_to(struct task_struct *prev,
account_process_vtime(current);
calculate_steal_time();
/*
* We can't take a PMU exception inside _switch() since there is a
* window where the kernel stack SLB and the kernel stack are out
* of sync. Hard disable here.
*/
hard_irq_disable();
last = _switch(old_thread, new_thread);
local_irq_restore(flags);

6
arch/powerpc/mm/slb.c
View file

@ -124,6 +124,12 @@ void slb_flush_and_rebolt(void)
ksp_vsid_data = get_slb_shadow()->save_area[2].vsid;
}
/*
* We can't take a PMU exception in the following code, so hard
* disable interrupts.
*/
hard_irq_disable();
/* We need to do this all in asm, so we're sure we don't touch
* the stack between the slbia and rebolting it. */
asm volatile("isync\n"