On 07/06/2016 03:32 PM, Steven Rostedt wrote:

On Wed, 6 Jul 2016 07:03:43 -0500
Corey Minyard [off-list ref] wrote:

quoted

quoted

---

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index aaf4b9b94f38..cc70d98a30f6 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c

@@ -1391,7 +1391,8 @@ static int mce_notify_work_init(void)
  
  static void mce_notify_work(void)
  {
-	wake_up_process(mce_notify_helper);
+	if (mce_notify_helper)
+		wake_up_process(mce_notify_helper);
  }

Actually, this appears to be the fix in 4.6-rt.

This is in there since it was switched to swork instead of using its
own thread and is also in v4.1:

https://git.kernel.org/cgit/linux/kernel/git/rt/linux-rt-devel.git/tree/arch/x86/kernel/cpu/mcheck/mce.c?h=linux-4.1.y-rt#n1387

as part of x86-mce-use-swait-queue-for-mce-wakeups.patch. And this
patch was first part of v3.18.9-rt4 as a new patch dropping x86-mce-
Defer-mce-wakeups-to-threads-for-PREEMPT_RT.patch.

-- Steve

Sebastian