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Subject[PATCH] intel_idle: replace conditionals with static_cpu_has(X86_FEATURE_ARAT)
Date
If the 'arat' cpu flag is set, then the conditionals in intel_idle() that
guard calling tick_broadcast_enter()/exit() will never be true. Use
static_cpu_has(X86_FEATURE_ARAT) to create a fast path to replace
the conditional.

Signed-off-by: Jason Baron <jbaron@akamai.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/idle/intel_idle.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 5dc7ea4..5db5e31 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -913,8 +913,7 @@ static __cpuidle int intel_idle(struct cpuidle_device *dev,
struct cpuidle_state *state = &drv->states[index];
unsigned long eax = flg2MWAIT(state->flags);
unsigned int cstate;
-
- cstate = (((eax) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK) + 1;
+ bool uninitialized_var(tick);

/*
* NB: if CPUIDLE_FLAG_TLB_FLUSHED is set, this idle transition
@@ -923,12 +922,19 @@ static __cpuidle int intel_idle(struct cpuidle_device *dev,
* useful with this knowledge.
*/

- if (!(lapic_timer_reliable_states & (1 << (cstate))))
- tick_broadcast_enter();
+ if (!static_cpu_has(X86_FEATURE_ARAT)) {
+ cstate = (((eax) >> MWAIT_SUBSTATE_SIZE) &
+ MWAIT_CSTATE_MASK) + 1;
+ tick = false;
+ if (!(lapic_timer_reliable_states & (1 << (cstate)))) {
+ tick = true;
+ tick_broadcast_enter();
+ }
+ }

mwait_idle_with_hints(eax, ecx);

- if (!(lapic_timer_reliable_states & (1 << (cstate))))
+ if (!static_cpu_has(X86_FEATURE_ARAT) && tick)
tick_broadcast_exit();

return index;
--
2.6.1
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