Re: [PATCH][RT] x86: Fix an RT MCE crash

[Steven Rostedt <rostedt@goodmis.org>]

On Thu, 30 Jun 2016 09:49:19 -0500
Corey Minyard <minyard@acm.org> wrote:

> On 06/30/2016 08:43 AM, Steven Rostedt wrote:
> > On Thu, 30 Jun 2016 08:24:49 -0500
> > minyard@acm.org wrote:
> >  
> >> From: Corey Minyard <cminyard@mvista.com>
> >>
> >> On some x86 systems an MCE interrupt would come in before the kernel
> >> was ready for it.  Looking at the latest RT code, it has similar
> >> (but not quite the same) code, except it adds a bool that tells if
> >> MCE handling is initialized.  Add the same bool for older versions.
> >>
> >> Signed-off-by: Corey Minyard <cminyard@mvista.com>
> >> ---
> >>   arch/x86/kernel/cpu/mcheck/mce.c | 5 ++++-
> >>   1 file changed, 4 insertions(+), 1 deletion(-)
> >>
> >> We noticed this issue on a new Broadwell system when we booted RT
> >> on it.  This patch is for 3.10, I'm not sure if it applies to
> >> other kernel versions.  
> > Do you mean other 'older' versions? and that this works with the
> > versions after 3.10 without this patch?  
> 
> I haven't look at supported kernel versions besides 3.10 and 4.4.
> The fix was from the 4.4 version of this code.  This patch fixes
> v3.10-rt; I can look at finding which other versions need this.  I
> was planning to do this, but I wanted to get the patch out for
> comments first.

I'm not an MCE expert (I just Cc'd one though ;-)

OK, so you are saying that the fix was from 4.4-rt? I can go and look
for it, and if so, I can add it to the "backport" patches I need to do.
Which I need to go and do that soon (backport patches from previous
versions). It may already be in that list.

-- Steve

> 
> -corey
> 
> > -- Steve
> >  
> >> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> >> index aaf4b9b..7125584 100644
> >> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> >> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> >> @@ -1365,6 +1365,7 @@ static void __mce_notify_work(void)
> >>   }
> >>   
> >>   #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)
> >>   	if (!mce_notify_helper)
> >>   		return -ENOMEM;
> >>   
> >> +	notify_work_ready = true;
> >>   	return 0;
> >>   }
> >>   
> >>   static void mce_notify_work(void)
> >>   {
> >> -	wake_up_process(mce_notify_helper);
> >> +	if (notify_work_ready)
> >> +		wake_up_process(mce_notify_helper);
> >>   }
> >>   #else
> >>   static void mce_notify_work(void)