[PATCH 04/36] cpuidle,intel_idle: Fix CPUIDLE_FLAG_IRQ_ENABLE

[Peter Zijlstra <peterz@xxxxxxxxxxxxx>]

Commit c227233ad64c ("intel_idle: enable interrupts before C1 on
Xeons") wrecked intel_idle in two ways:

 - must not have tracing in idle functions
 - must return with IRQs disabled

Additionally, it added a branch for no good reason.

Fixes: c227233ad64c ("intel_idle: enable interrupts before C1 on Xeons")
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 drivers/idle/intel_idle.c |   48 +++++++++++++++++++++++++++++++++++-----------
 1 file changed, 37 insertions(+), 11 deletions(-)

--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -129,21 +137,37 @@ static unsigned int mwait_substates __in
  *
  * Must be called under local_irq_disable().
  */
+
-static __cpuidle int intel_idle(struct cpuidle_device *dev,
-                               struct cpuidle_driver *drv, int index)
+static __always_inline int __intel_idle(struct cpuidle_device *dev,
+                                       struct cpuidle_driver *drv, int index)
 {
        struct cpuidle_state *state = &drv->states[index];
        unsigned long eax = flg2MWAIT(state->flags);
        unsigned long ecx = 1; /* break on interrupt flag */
 
-       if (state->flags & CPUIDLE_FLAG_IRQ_ENABLE)
-               local_irq_enable();
-
        mwait_idle_with_hints(eax, ecx);
 
        return index;
 }
 
+static __cpuidle int intel_idle(struct cpuidle_device *dev,
+                               struct cpuidle_driver *drv, int index)
+{
+       return __intel_idle(dev, drv, index);
+}
+
+static __cpuidle int intel_idle_irq(struct cpuidle_device *dev,
+                                   struct cpuidle_driver *drv, int index)
+{
+       int ret;
+
+       raw_local_irq_enable();
+       ret = __intel_idle(dev, drv, index);
+       raw_local_irq_disable();
+
+       return ret;
+}
+
 /**
  * intel_idle_s2idle - Ask the processor to enter the given idle state.
  * @dev: cpuidle device of the target CPU.
@@ -1801,6 +1824,9 @@ static void __init intel_idle_init_cstat
                /* Structure copy. */
                drv->states[drv->state_count] = cpuidle_state_table[cstate];
 
+               if (cpuidle_state_table[cstate].flags & CPUIDLE_FLAG_IRQ_ENABLE)
+                       drv->states[drv->state_count].enter = intel_idle_irq;
+
                if ((disabled_states_mask & BIT(drv->state_count)) ||
                    ((icpu->use_acpi || force_use_acpi) &&
                     intel_idle_off_by_default(mwait_hint) &&