The patch titled
Convert cpu hotplug notifiers to use raw_notifier instead of blocking_notifier
has been added to the -mm tree. Its filename is
convert-cpu-hotplug-notifiers-to-use-raw_notifier-instead-of-blocking_notifier.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: Convert cpu hotplug notifiers to use raw_notifier instead of blocking_notifier
From: Neil Brown <neilb@xxxxxxx>
The use of blocking notifier by _cpu_up and _cpu_down in cpu.c has two
problem.
1/ An interaction with the workqueue notifier causes lockdep to spit a
warning.
2/ A notifier could conceivable be added or removed while _cpu_up or
_cpu_down are in process. As each notifier is called twice (prepare
then commit/abort) this could be unhealthy.
To fix to we simply take cpu_add_remove_lock while adding or removing
notifiers to/from the list.
This makes the 'blocking' usage unnecessary as all accesses to cpu_chain
are now protected by cpu_add_remove_lock. So change "blocking" to "raw" in
all relevant places. This fixes 1.
Credit: Andrew Morton
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Michal Piotrowski <michal.k.k.piotrowski@xxxxxxxxx> (reporter)
Signed-off-by: Neil Brown <neilb@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
kernel/cpu.c | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)
diff -puN kernel/cpu.c~convert-cpu-hotplug-notifiers-to-use-raw_notifier-instead-of-blocking_notifier kernel/cpu.c
--- a/kernel/cpu.c~convert-cpu-hotplug-notifiers-to-use-raw_notifier-instead-of-blocking_notifier
+++ a/kernel/cpu.c
@@ -19,7 +19,7 @@
static DEFINE_MUTEX(cpu_add_remove_lock);
static DEFINE_MUTEX(cpu_bitmask_lock);
-static __cpuinitdata BLOCKING_NOTIFIER_HEAD(cpu_chain);
+static __cpuinitdata RAW_NOTIFIER_HEAD(cpu_chain);
/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
* Should always be manipulated under cpu_add_remove_lock
@@ -68,7 +68,11 @@ EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);
/* Need to know about CPUs going up/down? */
int __cpuinit register_cpu_notifier(struct notifier_block *nb)
{
- return blocking_notifier_chain_register(&cpu_chain, nb);
+ int ret;
+ mutex_lock(&cpu_add_remove_lock);
+ ret = raw_notifier_chain_register(&cpu_chain, nb);
+ mutex_unlock(&cpu_add_remove_lock);
+ return ret;
}
#ifdef CONFIG_HOTPLUG_CPU
@@ -77,7 +81,9 @@ EXPORT_SYMBOL(register_cpu_notifier);
void unregister_cpu_notifier(struct notifier_block *nb)
{
- blocking_notifier_chain_unregister(&cpu_chain, nb);
+ mutex_lock(&cpu_add_remove_lock);
+ raw_notifier_chain_unregister(&cpu_chain, nb);
+ mutex_unlock(&cpu_add_remove_lock);
}
EXPORT_SYMBOL(unregister_cpu_notifier);
@@ -126,7 +132,7 @@ static int _cpu_down(unsigned int cpu)
if (!cpu_online(cpu))
return -EINVAL;
- err = blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
+ err = raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
(void *)(long)cpu);
if (err == NOTIFY_BAD) {
printk("%s: attempt to take down CPU %u failed\n",
@@ -146,7 +152,7 @@ static int _cpu_down(unsigned int cpu)
if (IS_ERR(p)) {
/* CPU didn't die: tell everyone. Can't complain. */
- if (blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
+ if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
(void *)(long)cpu) == NOTIFY_BAD)
BUG();
@@ -169,7 +175,7 @@ static int _cpu_down(unsigned int cpu)
put_cpu();
/* CPU is completely dead: tell everyone. Too late to complain. */
- if (blocking_notifier_call_chain(&cpu_chain, CPU_DEAD,
+ if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD,
(void *)(long)cpu) == NOTIFY_BAD)
BUG();
@@ -206,7 +212,7 @@ static int __devinit _cpu_up(unsigned in
if (cpu_online(cpu) || !cpu_present(cpu))
return -EINVAL;
- ret = blocking_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
+ ret = raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
if (ret == NOTIFY_BAD) {
printk("%s: attempt to bring up CPU %u failed\n",
__FUNCTION__, cpu);
@@ -223,11 +229,11 @@ static int __devinit _cpu_up(unsigned in
BUG_ON(!cpu_online(cpu));
/* Now call notifier in preparation. */
- blocking_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
+ raw_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
out_notify:
if (ret != 0)
- blocking_notifier_call_chain(&cpu_chain,
+ raw_notifier_call_chain(&cpu_chain,
CPU_UP_CANCELED, hcpu);
return ret;
_
Patches currently in -mm which might be from neilb@xxxxxxx are
origin.patch
md-fix-proc-mdstat-refcounting.patch
lockdep-annotate-nfs-nfsd-in-kernel-sockets.patch
lockdep-annotate-nfs-nfsd-in-kernel-sockets-tidy.patch
convert-cpu-hotplug-notifiers-to-use-raw_notifier-instead-of-blocking_notifier.patch
remove-lock_key-approach-to-managing-nested-bd_mutex-locks.patch
simplify-some-aspects-of-bd_mutex-nesting.patch
use-mutex_lock_nested-for-bd_mutex-to-avoid-lockdep-warning.patch
avoid-lockdep-warning-in-md.patch
knfsd-add-nfs-export-support-to-tmpfs.patch
md-conditionalize-some-code.patch
md-dm-reduce-stack-usage-with-stacked-block-devices.patch
-
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