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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: Alan 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: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Alan Stern 2006-10-04 02:17:06 -07:00 committed by Linus Torvalds
parent e6a92013ba
commit b4dfdbb3c7
1 changed files with 13 additions and 7 deletions
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20
drivers/cpufreq/cpufreq.c
View File

@ -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: