path: root/arch
diff options
authorPaul Mackerras <paulus@samba.org>2010-08-10 20:38:23 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2010-08-31 11:35:13 +1000
commitb0d278b7d3ae9115939ddcea93f516308cc367e2 (patch)
tree82584f3fff6aede6423193784b7edb75c9b892fa /arch
parent4562c986f0d694124de20815adf7e1aad8a94668 (diff)
powerpc/perf_event: Reduce latency of calling perf_event_do_pending
Commit 0fe1ac48 ("powerpc/perf_event: Fix oops due to perf_event_do_pending call") moved the call to perf_event_do_pending in timer_interrupt() down so that it was after the irq_enter() call. Unfortunately this moved it after the code that checks whether it is time for the next decrementer clock event. The result is that the call to perf_event_do_pending() won't happen until the next decrementer clock event is due. This was pointed out by Milton Miller. This fixes it by moving the check for whether it's time for the next decrementer clock event down to the point where we're about to call the event handler, after we've called perf_event_do_pending. This has the side effect that on old pre-Core99 Powermacs where we use the ppc_n_lost_interrupts mechanism to replay interrupts, a replayed interrupt will incur a little more latency since it will now do the code from the irq_enter down to the irq_exit, that it used to skip. However, these machines are now old and rare enough that this doesn't matter. To make it clear that ppc_n_lost_interrupts is only used on Powermacs, and to speed up the code slightly on non-Powermac ppc32 machines, the code that tests ppc_n_lost_interrupts is now conditional on CONFIG_PMAC as well as CONFIG_PPC32. 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')
1 files changed, 11 insertions, 12 deletions
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index ce53dfa7130..8533b3b83f5 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -577,20 +577,11 @@ void timer_interrupt(struct pt_regs * regs)
* some CPUs will continuue to take decrementer exceptions */
-#ifdef CONFIG_PPC32
+#if defined(CONFIG_PPC32) && defined(CONFIG_PMAC)
if (atomic_read(&ppc_n_lost_interrupts) != 0)
- now = get_tb_or_rtc();
- if (now < decrementer->next_tb) {
- /* not time for this event yet */
- now = decrementer->next_tb - now;
- if (now <= DECREMENTER_MAX)
- set_dec((int)now);
- trace_timer_interrupt_exit(regs);
- return;
- }
old_regs = set_irq_regs(regs);
@@ -606,8 +597,16 @@ void timer_interrupt(struct pt_regs * regs)
get_lppaca()->int_dword.fields.decr_int = 0;
- if (evt->event_handler)
- evt->event_handler(evt);
+ now = get_tb_or_rtc();
+ if (now >= decrementer->next_tb) {
+ decrementer->next_tb = ~(u64)0;
+ if (evt->event_handler)
+ evt->event_handler(evt);
+ } else {
+ now = decrementer->next_tb - now;
+ if (now <= DECREMENTER_MAX)
+ set_dec((int)now);
+ }
if (firmware_has_feature(FW_FEATURE_ISERIES) && hvlpevent_is_pending())