Patch "cpuidle / menu: Return (-1) if there are no suitable states" has been added to the 3.10-stable tree

This is a note to let you know that I've just added the patch titled

cpuidle / menu: Return (-1) if there are no suitable states

to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
cpuidle-menu-return-1-if-there-are-no-suitable-states.patch
and it can be found in the queue-3.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: "Rafael J. Wysocki" <[email protected]>
Date: Thu, 1 May 2014 00:14:04 +0200
Subject: cpuidle / menu: Return (-1) if there are no suitable states

From: "Rafael J. Wysocki" <[email protected]>

commit 3836785a1bdcd6706c68ad46bf53adc0b057b310 upstream.

If there is a PM QoS latency limit and all of the sufficiently shallow C-states are disabled, the cpuidle menu governor returns 0 which on some systems is CPUIDLE_DRIVER_STATE_START and shouldn't be returned if that C-state has been disabled.

Fix the issue by modifying the menu governor to return (-1) in such situations.

[shilpab: Backport to 3.10.y
- adjust context
- add a check if 'next_state' is less than 0 in 'cpuidle_idle_call()', this ensures that we exit 'cpuidle_idle_call()' if governor->select() returns negative value]

---
 drivers/cpuidle/cpuidle.c        |    3 +++
 drivers/cpuidle/governors/menu.c |    2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

@@ -135,6 +135,9 @@ int cpuidle_idle_call(void)
 
 	/* ask the governor for the next state */
 	next_state = cpuidle_curr_governor->select(drv, dev);
+	if (next_state < 0)
+		return -EBUSY;
+
 	if (need_resched()) {
 		dev->last_residency = 0;
 		/* give the governor an opportunity to reflect on the outcome */

@@ -269,7 +269,7 @@ static int menu_select(struct cpuidle_dr
 		data->needs_update = 0;
 	}
 
-	data->last_state_idx = 0;
+	data->last_state_idx = CPUIDLE_DRIVER_STATE_START - 1;
 	data->exit_us = 0;
 
 	/* Special case when user has set very strict latency requirement */

Patches currently in stable-queue which might be from [email protected] are

queue-3.10/cpuidle-menu-return-1-if-there-are-no-suitable-states.patch