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authorPaul Mackerras <paulus@samba.org>2010-04-13 16:46:04 -0400
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2010-05-12 00:34:00 -0400
commit0fe1ac48bef018bed896307cd12f6ca9b5e704ab (patch)
tree6f5e68619798312ee808f23c1a0cc5799a131545 /arch/powerpc/kernel/entry_64.S
parentcea0d767c29669bf89f86e4aee46ef462d2ebae8 (diff)
powerpc/perf_event: Fix oops due to perf_event_do_pending call
Anton Blanchard found that large POWER systems would occasionally crash in the exception exit path when profiling with perf_events. The symptom was that an interrupt would occur late in the exit path when the MSR[RI] (recoverable interrupt) bit was clear. Interrupts should be hard-disabled at this point but they were enabled. Because the interrupt was not recoverable the system panicked. The reason is that the exception exit path was calling perf_event_do_pending after hard-disabling interrupts, and perf_event_do_pending will re-enable interrupts. The simplest and cleanest fix for this is to use the same mechanism that 32-bit powerpc does, namely to cause a self-IPI by setting the decrementer to 1. This means we can remove the tests in the exception exit path and raw_local_irq_restore. This also makes sure that the call to perf_event_do_pending from timer_interrupt() happens within irq_enter/irq_exit. (Note that calling perf_event_do_pending from timer_interrupt does not mean that there is a possible 1/HZ latency; setting the decrementer to 1 ensures that the timer interrupt will happen immediately, i.e. within one timebase tick, which is a few nanoseconds or 10s of nanoseconds.) Signed-off-by: Paul Mackerras <paulus@samba.org> Cc: stable@kernel.org Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/kernel/entry_64.S')
-rw-r--r--arch/powerpc/kernel/entry_64.S9
1 files changed, 0 insertions, 9 deletions
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 07109d843787..42e9d908914a 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -556,15 +556,6 @@ ALT_FW_FTR_SECTION_END_IFCLR(FW_FEATURE_ISERIES)
5562: 5562:
557 TRACE_AND_RESTORE_IRQ(r5); 557 TRACE_AND_RESTORE_IRQ(r5);
558 558
559#ifdef CONFIG_PERF_EVENTS
560 /* check paca->perf_event_pending if we're enabling ints */
561 lbz r3,PACAPERFPEND(r13)
562 and. r3,r3,r5
563 beq 27f
564 bl .perf_event_do_pending
56527:
566#endif /* CONFIG_PERF_EVENTS */
567
568 /* extract EE bit and use it to restore paca->hard_enabled */ 559 /* extract EE bit and use it to restore paca->hard_enabled */
569 ld r3,_MSR(r1) 560 ld r3,_MSR(r1)
570 rldicl r4,r3,49,63 /* r0 = (r3 >> 15) & 1 */ 561 rldicl r4,r3,49,63 /* r0 = (r3 >> 15) & 1 */