Re: [perf/x86] 8de4a00661: WARNING: CPU: 0 PID: 1 at kernel/locking/mutex-debug.c:80 debug_mutex_unlock+0x20c/0x2b3

[Thomas Gleixner]

On Tue, 12 Jul 2016, Thomas Gleixner wrote:
> /me goes digging deeper

and dons a brown paperbag....

8<----------------

Subject: cpuhotplug: Keep enough storage space if SMP=n
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

The cpuhp_bp_states array is cut short when CONFIG_SMP=n, but the dynamically
registered callbacks are stored nevertheless and happily scribble outside of
the array bounds.

We need to store them in case that the state is unregistered so we can invoke
the teardown function. That's independent of CONFIG_SMP. Make sure the array
is large enough.

Fixes: cff7d378d3fd "cpu/hotplug: Convert to a state machine for the control processor"
Reported-by: kernel test robot <xiaolong.ye@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

---
diff --git a/kernel/cpu.c b/kernel/cpu.c
index d948e44c471e..7b61887f7ccd 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1201,6 +1201,8 @@ static struct cpuhp_step cpuhp_bp_states[] = {
 		.teardown		= takedown_cpu,
 		.cant_stop		= true,
 	},
+#else
+	[CPUHP_BRINGUP_CPU] = { },
 #endif
 };