From: Lai Jiangshan <[email protected]>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
commit 4bee96860a65c3a62d332edac331b3cf936ba3ad upstream.
The following race exists in the smpboot percpu threads management:
CPU0 CPU1
cpu_up(2)
get_online_cpus();
smpboot_create_threads(2);
smpboot_register_percpu_thread();
for_each_online_cpu();
__smpboot_create_thread();
__cpu_up(2);
This results in a missing per cpu thread for the newly onlined cpu2 and
in a NULL pointer dereference on a consecutive offline of that cpu.
Proctect smpboot_register_percpu_thread() with get_online_cpus() to
prevent that.
[ tglx: Massaged changelog and removed the change in
smpboot_unregister_percpu_thread() because that's an
optimization and therefor not stable material. ]
Signed-off-by: Lai Jiangshan <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Rusty Russell <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Srivatsa S. Bhat <[email protected]>
Cc: David Rientjes <[email protected]>
Link:
http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Jiri Slaby <[email protected]>
---
kernel/smpboot.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/kernel/smpboot.c b/kernel/smpboot.c
index eb89e1807408..60d35ac5d3f1 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);
--
2.2.2
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
