If the smpboot_register_percpu_thread() is called after smpboot_create_threads()
but before __cpu_up(), the smpboot thread of the online-ing CPU is not created,
and it results a bug. So we use get_online_cpus() to prevent it.
smpboot_unregister_percpu_thread() travels all possible CPU, it doesn't need
get_online_cpus() which is removed in the patch.
CC: Thomas Gleixner <t...@linutronix.de>
Cc: Rusty Russell <ru...@rustcorp.com.au>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Srivatsa S. Bhat <srivatsa.b...@linux.vnet.ibm.com>
CC: sta...@kernel.org
Signed-off-by: Lai Jiangshan <la...@cn.fujitsu.com>
---
kernel/smpboot.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/smpboot.c b/kernel/smpboot.c
index eb89e18..8adab87 100644
--- a/kernel/smpboot.c
+++ b/kernel/smpboot.c
@@ -279,6 +279,7 @@ int smpboot_register_percpu_thread(struct
smp_hotplug_thread *plug_thread)
unsigned int cpu;
int ret = 0;
+ get_online_cpus();
mutex_lock(&smpboot_threads_lock);
for_each_online_cpu(cpu) {
ret = __smpboot_create_thread(plug_thread, cpu);
@@ -291,6 +292,7 @@ int smpboot_register_percpu_thread(struct
smp_hotplug_thread *plug_thread)
list_add(&plug_thread->list, &hotplug_threads);
out:
mutex_unlock(&smpboot_threads_lock);
+ put_online_cpus();
return ret;
}
EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread);
@@ -303,11 +305,9 @@ EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread);
*/
void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread)
{
- get_online_cpus();
mutex_lock(&smpboot_threads_lock);
list_del(&plug_thread->list);
smpboot_destroy_threads(plug_thread);
mutex_unlock(&smpboot_threads_lock);
- put_online_cpus();
}
EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread);
--
1.7.4.4
--
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