The patch titled
cpufreq: make the transition_notifier chain use SRCU
has been added to the -mm tree. Its filename is
cpufreq-make-the-transition_notifier-chain-use-srcu.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: cpufreq: make the transition_notifier chain use SRCU
From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Cc: Jesse Brandeburg <jesse.brandeburg@xxxxxxxxx>
Cc: Dave Jones <davej@xxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
drivers/cpufreq/cpufreq.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
diff -puN drivers/cpufreq/cpufreq.c~cpufreq-make-the-transition_notifier-chain-use-srcu drivers/cpufreq/cpufreq.c
--- a/drivers/cpufreq/cpufreq.c~cpufreq-make-the-transition_notifier-chain-use-srcu
+++ a/drivers/cpufreq/cpufreq.c
@@ -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 cp
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_de
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_dev
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 not
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 n
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:
_
Patches currently in -mm which might be from stern@xxxxxxxxxxxxxxxxxxx are
e100-disable-interrupts-at-boot.patch
usb-hub-driver-improve-use-of-ifdef-fix.patch
properly-unregister-reboot-notifier-in-case-of-failure-in-ehci-hcd.patch
uhci-dont-test-the-short-packet-detect-bit.patch
block-layer-early-detection-of-medium-not-present.patch
scsi-core-and-sd-early-detection-of-medium-not-present.patch
sd-early-detection-of-medium-not-present.patch
scsi-early-detection-of-medium-not-present-updated.patch
add-srcu-based-notifier-chains.patch
srcu-report-out-of-memory-errors.patch
srcu-report-out-of-memory-errors-fixlet.patch
cpufreq-make-the-transition_notifier-chain-use-srcu.patch
-
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