diff options
authorAnton Blanchard <anton@samba.org>2011-11-23 20:07:17 +0000
committerGreg Kroah-Hartman <gregkh@suse.de>2012-01-12 11:29:22 -0800
commit8e04782a06882913304916bc60960e4fc7405e18 (patch)
parentf92fed3f1de1942a61978c5e59bbed56eab4ac55 (diff)
powerpc/time: Handle wrapping of decrementer
commit 37fb9a0231ee43d42d069863bdfd567fca2b61af upstream. When re-enabling interrupts we have code to handle edge sensitive decrementers by resetting the decrementer to 1 whenever it is negative. If interrupts were disabled long enough that the decrementer wrapped to positive we do nothing. This means interrupts can be delayed for a long time until it finally goes negative again. While we hope interrupts are never be disabled long enough for the decrementer to go positive, we have a very good test team that can drive any kernel into the ground. The softlockup data we get back from these fails could be seconds in the future, completely missing the cause of the lockup. We already keep track of the timebase of the next event so use that to work out if we should trigger a decrementer exception. Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
3 files changed, 17 insertions, 9 deletions
diff --git a/arch/powerpc/include/asm/time.h b/arch/powerpc/include/asm/time.h
index fe6f7c2c9c6..bc3c745cb90 100644
--- a/arch/powerpc/include/asm/time.h
+++ b/arch/powerpc/include/asm/time.h
@@ -219,5 +219,7 @@ DECLARE_PER_CPU(struct cpu_usage, cpu_usage_array);
extern void secondary_cpu_time_init(void);
extern void iSeries_time_init_early(void);
+extern void decrementer_check_overflow(void);
#endif /* __KERNEL__ */
#endif /* __POWERPC_TIME_H */
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 5c3c46948d9..745c1e7c10f 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -164,16 +164,13 @@ notrace void arch_local_irq_restore(unsigned long en)
local_paca->hard_enabled = en;
- /* On server, re-trigger the decrementer if it went negative since
- * some processors only trigger on edge transitions of the sign bit.
- *
- * BookE has a level sensitive decrementer (latches in TSR) so we
- * don't need that
+ /*
+ * Trigger the decrementer if we have a pending event. Some processors
+ * only trigger on edge transitions of the sign bit. We might also
+ * have disabled interrupts long enough that the decrementer wrapped
+ * to positive.
- if ((int)mfspr(SPRN_DEC) < 0)
- mtspr(SPRN_DEC, 1);
-#endif /* CONFIG_BOOKE */
+ decrementer_check_overflow();
* Force the delivery of pending soft-disabled interrupts on PS3.
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 522bb1dfc35..5db163c9675 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -889,6 +889,15 @@ static void __init clocksource_init(void)
clock->name, clock->mult, clock->shift);
+void decrementer_check_overflow(void)
+ u64 now = get_tb_or_rtc();
+ struct decrementer_clock *decrementer = &__get_cpu_var(decrementers);
+ if (now >= decrementer->next_tb)
+ set_dec(1);
static int decrementer_set_next_event(unsigned long evt,
struct clock_event_device *dev)