cpuidle: always return with interrupts enabled

In the case where cpuidle_idle_call() returns before changing state due to
a need_resched(), it was returning with IRQs disabled.

The idle path assumes that the platform specific idle code returns with
interrupts enabled (although this too is undocumented AFAICT) and on ARM
we have a WARN_ON(!(irqs_disabled()) when returning from the idle loop, so
the user-visible effects were only a warning since interrupts were
eventually re-enabled later.

On x86, this same problem exists, but there is no WARN_ON() to detect it.
As on ARM, the interrupts are eventually re-enabled, so I'm not sure of
any actual bugs triggered by this.  It's primarily a
correctness/consistency fix.

This patch ensures IRQs are (re)enabled before returning.

Reported-by: Hemanth V <hemanthv@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Tested-by: Martin Michlmayr <tbm@cyrius.com>
Cc: <stable@kernel.org>		[2.6.31.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index ad41f19b8e3f..12fdd3987a36 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -76,8 +76,11 @@ static void cpuidle_idle_call(void)
 #endif
         /* ask the governor for the next state */
         next_state = cpuidle_curr_governor->select(dev);
-        if (need_resched())
+        if (need_resched()) {
+                local_irq_enable();
                 return;
+        }
+
         target_state = &dev->states[next_state];
 
         /* enter the state and update stats */