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>
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 5939e7f..a4166e2 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -881,6 +881,7 @@
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 @@
* 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 @@
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 @@
}
local_irq_disable();
+
if (cx->entry_method != ACPI_CSTATE_FFH) {
current_thread_info()->status &= ~TS_POLLING;
/*
@@ -975,12 +978,12 @@
* 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 @@
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++;