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authorGautham R Shenoy <ego@in.ibm.com>2007-05-09 02:34:03 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-09 12:30:51 -0700
commitbaaca49f415b25fdbe2a8f3c22b39929e450fbfd (patch)
treeb152b4235fc07fe56619bd3a2e975e5ca90b8c5b
parent6f7cc11aa6c7d5002e16096c7590944daece70ed (diff)
Define and use new events,CPU_LOCK_ACQUIRE and CPU_LOCK_RELEASE
This is an attempt to provide an alternate mechanism for postponing a hotplug event instead of using a global mechanism like lock_cpu_hotplug. The proposal is to add two new events namely CPU_LOCK_ACQUIRE and CPU_LOCK_RELEASE. The notification for these two events would be sent out before and after a cpu_hotplug event respectively. During the CPU_LOCK_ACQUIRE event, a cpu-hotplug-aware subsystem is supposed to acquire any per-subsystem hotcpu mutex ( Eg. workqueue_mutex in kernel/workqueue.c ). During the CPU_LOCK_RELEASE release event the cpu-hotplug-aware subsystem is supposed to release the per-subsystem hotcpu mutex. The reasons for defining new events as opposed to reusing the existing events like CPU_UP_PREPARE/CPU_UP_FAILED/CPU_ONLINE for locking/unlocking of per-subsystem hotcpu mutexes are as follow: - CPU_LOCK_ACQUIRE: All hotcpu mutexes are taken before subsystems start handling pre-hotplug events like CPU_UP_PREPARE/CPU_DOWN_PREPARE etc, thus ensuring a clean handling of these events. - CPU_LOCK_RELEASE: The hotcpu mutexes will be released only after all subsystems have handled post-hotplug events like CPU_DOWN_FAILED, CPU_DEAD,CPU_ONLINE etc thereby ensuring that there are no subsequent clashes amongst the interdependent subsystems after a cpu hotplugs. This patch also uses __raw_notifier_call chain in _cpu_up to take care of the dependency between the two consequetive calls to raw_notifier_call_chain. [akpm@linux-foundation.org: fix a bug] Signed-off-by: Gautham R Shenoy <ego@in.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/notifier.h2
-rw-r--r--kernel/cpu.c19
2 files changed, 16 insertions, 5 deletions
diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index e34221bf8946..1903e5490c04 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -194,6 +194,8 @@ extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
#define CPU_DOWN_PREPARE 0x0005 /* CPU (unsigned)v going down */
#define CPU_DOWN_FAILED 0x0006 /* CPU (unsigned)v NOT going down */
#define CPU_DEAD 0x0007 /* CPU (unsigned)v dead */
+#define CPU_LOCK_ACQUIRE 0x0008 /* Acquire all hotcpu locks */
+#define CPU_LOCK_RELEASE 0x0009 /* Release all hotcpu locks */
#endif /* __KERNEL__ */
#endif /* _LINUX_NOTIFIER_H */
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 36e70845cfc3..48810498b355 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -132,12 +132,15 @@ static int _cpu_down(unsigned int cpu)
if (!cpu_online(cpu))
return -EINVAL;
+ raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE,
+ (void *)(long)cpu);
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",
__FUNCTION__, cpu);
- return -EINVAL;
+ err = -EINVAL;
+ goto out_release;
}
/* Ensure that we are not runnable on dying cpu */
@@ -185,6 +188,9 @@ out_thread:
err = kthread_stop(p);
out_allowed:
set_cpus_allowed(current, old_allowed);
+out_release:
+ raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE,
+ (void *)(long)cpu);
return err;
}
@@ -206,13 +212,15 @@ int cpu_down(unsigned int cpu)
/* Requires cpu_add_remove_lock to be held */
static int __cpuinit _cpu_up(unsigned int cpu)
{
- int ret;
+ int ret, nr_calls = 0;
void *hcpu = (void *)(long)cpu;
if (cpu_online(cpu) || !cpu_present(cpu))
return -EINVAL;
- ret = raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
+ raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu);
+ ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu,
+ -1, &nr_calls);
if (ret == NOTIFY_BAD) {
printk("%s: attempt to bring up CPU %u failed\n",
__FUNCTION__, cpu);
@@ -233,8 +241,9 @@ static int __cpuinit _cpu_up(unsigned int cpu)
out_notify:
if (ret != 0)
- raw_notifier_call_chain(&cpu_chain,
- CPU_UP_CANCELED, hcpu);
+ __raw_notifier_call_chain(&cpu_chain,
+ CPU_UP_CANCELED, hcpu, nr_calls, NULL);
+ raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE, hcpu);
return ret;
}

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