From: Anton Blanchard Date: Mon, 17 Mar 2008 04:27:09 +0000 (+1100) Subject: [POWERPC] Fix PMU + soft interrupt disable bug X-Git-Tag: v2.6.25-rc7~64^2~4 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=44387e9ff25267c78a99229aca55ed750e9174c7;p=linux-2.6 [POWERPC] Fix PMU + soft interrupt disable bug 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 Acked-by: Benjamin Herrenschmidt Acked-by: Olof Johansson Signed-off-by: Paul Mackerras --- diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 4846bf543a..59311ec0d4 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -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); diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c index 47b06bad24..906daeda59 100644 --- a/arch/powerpc/mm/slb.c +++ b/arch/powerpc/mm/slb.c @@ -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"