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Commit 9d359357 authored by John Kacur's avatar John Kacur Committed by Linus Torvalds
Browse files

pm_qos_requirement might sleep 



Make PM_QOS and CPU_IDLE play nicer when run with the RT-Preempt kernel.

The purpose of the patch is to remove the spin_lock around the read in the
function pm_qos_requirement - since spinlocks can sleep in -rt and this
function is called from idle.

CPU_IDLE polls the target_value's of some of the pm_qos parameters from
the idle loop causing sleeping locking warnings.  Changing the
target_value to an atomic avoids this issue.

Remove the spinlock in pm_qos_requirement by making target_value an atomic
type.

Signed-off-by: default avatarmark gross <mgross@linux.intel.com>
Signed-off-by: default avatarJohn Kacur <jkacur@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 74c4633d

kernel/pm_qos_params.c

+9 −16
Original line number Diff line number Diff line
@@ -43,7 +43,7 @@ 
#include <linux/uaccess.h>



/*

 * locking rule: all changes to target_value or requirements or notifiers lists

 * locking rule: all changes to requirements or notifiers lists

 * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock

 * held, taken with _irqsave.  One lock to rule them all

 */
@@ -66,7 +66,7 @@ struct pm_qos_object { 
	struct miscdevice pm_qos_power_miscdev;

	char *name;

	s32 default_value;

	s32 target_value;

	atomic_t target_value;

	s32 (*comparitor)(s32, s32);

};
@@ -77,7 +77,7 @@ static struct pm_qos_object cpu_dma_pm_qos = { 
	.notifiers = &cpu_dma_lat_notifier,

	.name = "cpu_dma_latency",

	.default_value = 2000 * USEC_PER_SEC,

	.target_value = 2000 * USEC_PER_SEC,

	.target_value = ATOMIC_INIT(2000 * USEC_PER_SEC),

	.comparitor = min_compare

};
@@ -87,7 +87,7 @@ static struct pm_qos_object network_lat_pm_qos = { 
	.notifiers = &network_lat_notifier,

	.name = "network_latency",

	.default_value = 2000 * USEC_PER_SEC,

	.target_value = 2000 * USEC_PER_SEC,

	.target_value = ATOMIC_INIT(2000 * USEC_PER_SEC),

	.comparitor = min_compare

};
@@ -99,7 +99,7 @@ static struct pm_qos_object network_throughput_pm_qos = { 
	.notifiers = &network_throughput_notifier,

	.name = "network_throughput",

	.default_value = 0,

	.target_value = 0,

	.target_value = ATOMIC_INIT(0),

	.comparitor = max_compare

};
@@ -150,11 +150,11 @@ static void update_target(int target) 
		extreme_value = pm_qos_array[target]->comparitor(

				extreme_value, node->value);

	}

	if (pm_qos_array[target]->target_value != extreme_value) {

	if (atomic_read(&pm_qos_array[target]->target_value) != extreme_value) {

		call_notifier = 1;

		pm_qos_array[target]->target_value = extreme_value;

		atomic_set(&pm_qos_array[target]->target_value, extreme_value);

		pr_debug(KERN_ERR "new target for qos %d is %d\n", target,

			pm_qos_array[target]->target_value);

			atomic_read(&pm_qos_array[target]->target_value));

	}

	spin_unlock_irqrestore(&pm_qos_lock, flags);
@@ -193,14 +193,7 @@ static int find_pm_qos_object_by_minor(int minor) 
 */

int pm_qos_requirement(int pm_qos_class)

{

	int ret_val;

	unsigned long flags;



	spin_lock_irqsave(&pm_qos_lock, flags);

	ret_val = pm_qos_array[pm_qos_class]->target_value;

	spin_unlock_irqrestore(&pm_qos_lock, flags);



	return ret_val;

	return atomic_read(&pm_qos_array[pm_qos_class]->target_value);

}

EXPORT_SYMBOL_GPL(pm_qos_requirement);