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pm_qos_requirement might sleep

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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: mark gross <mgross@linux.intel.com>
Signed-off-by: John Kacur <jkacur@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
John Kacur 2008-09-02 14:36:13 -07:00 committed by Linus Torvalds
parent 74c4633da7
commit 9d35935747
1 changed files with 9 additions and 16 deletions
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25
kernel/pm_qos_params.c
View file

@ -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);