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ACPI: acpi_idle: touch TS_POLLING only in the non-MWAIT case

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commit d306ebc286
(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>
This commit is contained in:
Len Brown 2010-05-24 14:27:44 -04:00
parent a7d27c3753
commit 02cf4f9808
1 changed files with 16 additions and 12 deletions
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28
drivers/acpi/processor_idle.c
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@ -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++;