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Commit b4dfdbb3 authored by Alan Stern's avatar Alan Stern Committed by Linus Torvalds
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[PATCH] cpufreq: make the transition_notifier chain use SRCU 



This patch (as762) changes the cpufreq_transition_notifier_list from a
blocking_notifier_head to an srcu_notifier_head.  This will prevent errors
caused attempting to call down_read() to access the notifier chain at a
time when interrupts must remain disabled, during system suspend.

It's not clear to me whether this is really necessary; perhaps the chain
could be made into an atomic_notifier.  However a couple of the callout
routines do use blocking operations, so this approach seems safer.

The head of the notifier chain needs to be initialized before use; this is
done by an __init routine at core_initcall time.  If this turns out not to
be a good choice, it can easily be changed.

Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: Jesse Brandeburg <jesse.brandeburg@gmail.com>
Cc: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent e6a92013

drivers/cpufreq/cpufreq.c

+13 −7
Original line number Diff line number Diff line
@@ -52,8 +52,14 @@ static void handle_update(void *data); 
 * The mutex locks both lists.

 */

static BLOCKING_NOTIFIER_HEAD(cpufreq_policy_notifier_list);

static BLOCKING_NOTIFIER_HEAD(cpufreq_transition_notifier_list);

static struct srcu_notifier_head cpufreq_transition_notifier_list;



static int __init init_cpufreq_transition_notifier_list(void)

{

	srcu_init_notifier_head(&cpufreq_transition_notifier_list);

	return 0;

}

core_initcall(init_cpufreq_transition_notifier_list);



static LIST_HEAD(cpufreq_governor_list);

static DEFINE_MUTEX (cpufreq_governor_mutex);
@@ -262,14 +268,14 @@ void cpufreq_notify_transition(struct cpufreq_freqs *freqs, unsigned int state) 
				freqs->old = policy->cur;

			}

		}

		blocking_notifier_call_chain(&cpufreq_transition_notifier_list,

		srcu_notifier_call_chain(&cpufreq_transition_notifier_list,

				CPUFREQ_PRECHANGE, freqs);

		adjust_jiffies(CPUFREQ_PRECHANGE, freqs);

		break;



	case CPUFREQ_POSTCHANGE:

		adjust_jiffies(CPUFREQ_POSTCHANGE, freqs);

		blocking_notifier_call_chain(&cpufreq_transition_notifier_list,

		srcu_notifier_call_chain(&cpufreq_transition_notifier_list,

				CPUFREQ_POSTCHANGE, freqs);

		if (likely(policy) && likely(policy->cpu == freqs->cpu))

			policy->cur = freqs->new;
@@ -1049,7 +1055,7 @@ static int cpufreq_suspend(struct sys_device * sysdev, pm_message_t pmsg) 
		freqs.old = cpu_policy->cur;

		freqs.new = cur_freq;



		blocking_notifier_call_chain(&cpufreq_transition_notifier_list,

		srcu_notifier_call_chain(&cpufreq_transition_notifier_list,

				    CPUFREQ_SUSPENDCHANGE, &freqs);

		adjust_jiffies(CPUFREQ_SUSPENDCHANGE, &freqs);
@@ -1130,7 +1136,7 @@ static int cpufreq_resume(struct sys_device * sysdev) 
			freqs.old = cpu_policy->cur;

			freqs.new = cur_freq;



			blocking_notifier_call_chain(

			srcu_notifier_call_chain(

					&cpufreq_transition_notifier_list,

					CPUFREQ_RESUMECHANGE, &freqs);

			adjust_jiffies(CPUFREQ_RESUMECHANGE, &freqs);
@@ -1176,7 +1182,7 @@ int cpufreq_register_notifier(struct notifier_block *nb, unsigned int list) 


	switch (list) {

	case CPUFREQ_TRANSITION_NOTIFIER:

		ret = blocking_notifier_chain_register(

		ret = srcu_notifier_chain_register(

				&cpufreq_transition_notifier_list, nb);

		break;

	case CPUFREQ_POLICY_NOTIFIER:
@@ -1208,7 +1214,7 @@ int cpufreq_unregister_notifier(struct notifier_block *nb, unsigned int list) 


	switch (list) {

	case CPUFREQ_TRANSITION_NOTIFIER:

		ret = blocking_notifier_chain_unregister(

		ret = srcu_notifier_chain_unregister(

				&cpufreq_transition_notifier_list, nb);

		break;

	case CPUFREQ_POLICY_NOTIFIER: