On 06/30/2016 06:01 PM, Borislav Petkov wrote:

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  #ifdef CONFIG_PREEMPT_RT_FULL
+static bool notify_work_ready __read_mostly;
  struct task_struct *mce_notify_helper;
  
  static int mce_notify_helper_thread(void *unused)

@@ -1386,12 +1387,14 @@ static int mce_notify_work_init(void)

Hmm, what is mce_notify_work_init() ?

This must be some RT-homegrown thing.

What it is supposed to do? Upstream is much different from 3.10 or
whatever that kernel version is.

The notify work snippet defers the execution of mce_notify_irq to a
kthread using swork (simple work, which is based on simple wait [1]).

mce_notify_irq() can't be run in IRQ context because of
wake_up_interruptible() which calls mutex_lock() eventually with
CONFIG_PREEMPT_RT_FULL.

cheers,
daniel

[1]
https://git.kernel.org/cgit/linux/kernel/git/rt/linux-rt-devel.git/tree/include/linux/swork.h?h=linux-4.6.y-rt

https://git.kernel.org/cgit/linux/kernel/git/rt/linux-rt-devel.git/tree/kernel/sched/swork.c?h=linux-4.6.y-rt