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authorLen Brown <len.brown@intel.com>2010-05-24 22:27:44 +0400
committerLen Brown <len.brown@intel.com>2010-05-28 21:58:57 +0400
commit02cf4f9808382af7265cafc33dc86ec5875526aa (patch)
tree6e4b7fc98a125e6af6011ee04e5fbf2d2fe38c4f
parenta7d27c37533524e23bbdc9ba1d78e3241b7483ea (diff)
downloadlinux-02cf4f9808382af7265cafc33dc86ec5875526aa.tar.xz
ACPI: acpi_idle: touch TS_POLLING only in the non-MWAIT case
commit d306ebc28649b89877a22158fe0076f06cc46f60 (ACPI: Be in TS_POLLING state during mwait based C-state entry) fixed an important power & performance issue where ACPI c2 and c3 C-states were clearing TS_POLLING even when using MWAIT (ACPI_STATE_FFH). That bug had been causing us to receive redundant scheduling interrups when we had already been woken up by MONITOR/MWAIT. Following up on that... In the MWAIT case, we don't have to subsequently check need_resched(), as that c heck was there for the TS_POLLING-clearing case. Note that not only does the cpuidle calling function already check need_resched() before calling us, the low-level entry into monitor/mwait calls it twice -- guaranteeing that a write to the trigger address can not go un-noticed. Also, in this case, we don't have to set TS_POLLING when we wake, because we never cleared it. Signed-off-by: Len Brown <len.brown@intel.com> Acked-by: Venkatesh Pallipadi <venki@google.com>
-rw-r--r--drivers/acpi/processor_idle.c28
1 files changed, 16 insertions, 12 deletions
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 5939e7f7d8e9..a4166e2abb92 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -881,6 +881,7 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
return(acpi_idle_enter_c1(dev, state));
local_irq_disable();
+
if (cx->entry_method != ACPI_CSTATE_FFH) {
current_thread_info()->status &= ~TS_POLLING;
/*
@@ -888,12 +889,12 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
* NEED_RESCHED:
*/
smp_mb();
- }
- if (unlikely(need_resched())) {
- current_thread_info()->status |= TS_POLLING;
- local_irq_enable();
- return 0;
+ if (unlikely(need_resched())) {
+ current_thread_info()->status |= TS_POLLING;
+ local_irq_enable();
+ return 0;
+ }
}
/*
@@ -918,7 +919,8 @@ static int acpi_idle_enter_simple(struct cpuidle_device *dev,
sched_clock_idle_wakeup_event(sleep_ticks*PM_TIMER_TICK_NS);
local_irq_enable();
- current_thread_info()->status |= TS_POLLING;
+ if (cx->entry_method != ACPI_CSTATE_FFH)
+ current_thread_info()->status |= TS_POLLING;
cx->usage++;
@@ -968,6 +970,7 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
}
local_irq_disable();
+
if (cx->entry_method != ACPI_CSTATE_FFH) {
current_thread_info()->status &= ~TS_POLLING;
/*
@@ -975,12 +978,12 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
* NEED_RESCHED:
*/
smp_mb();
- }
- if (unlikely(need_resched())) {
- current_thread_info()->status |= TS_POLLING;
- local_irq_enable();
- return 0;
+ if (unlikely(need_resched())) {
+ current_thread_info()->status |= TS_POLLING;
+ local_irq_enable();
+ return 0;
+ }
}
acpi_unlazy_tlb(smp_processor_id());
@@ -1032,7 +1035,8 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev,
sched_clock_idle_wakeup_event(sleep_ticks*PM_TIMER_TICK_NS);
local_irq_enable();
- current_thread_info()->status |= TS_POLLING;
+ if (cx->entry_method != ACPI_CSTATE_FFH)
+ current_thread_info()->status |= TS_POLLING;
cx->usage++;