[PATCH] Convert cpu hotplug notifiers to use raw_notifier instead of blocking_notifier
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@rustcorp.com.au>
Cc: Michal Piotrowski <michal.k.k.piotrowski@gmail.com> (reporter)
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 32c9662..27dd3ee 100644
--- a/kernel/cpu.c
+++ b/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 @@
/* 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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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;