lkml.org 
[lkml]   [2021]   [Aug]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] x86/mce/dev-mcelog: Call mce_register_decode_chain() much earlier
On Fri, Aug 20, 2021 at 05:48:21PM +0200, Borislav Petkov wrote:
> On Fri, Aug 20, 2021 at 07:43:14AM -0700, Luck, Tony wrote:
> > How can the kernel tell that all consumers have registered? Is there
> > some new kernel crystal ball functionality that can predict that an
> > EDAC driver module is going to be loaded at some point in the future
> > when user space is up and running :-)
>
> The crystal ball is called mcheck_late_init(). There's even:
>
> /*
> * Flush out everything that has been logged during early boot, now that
> * everything has been initialized (workqueues, decoders, ...).
> */
> mce_schedule_work();
>
> in there. That thing is late_initcall() and by that time mcelog should
> have been registered. And I wonder why isn't that working as expected...
>
> > I think the best we could do would be to set a timer for some point
> > far enough out (one minute?, two minutes?) to give a chance for
> > modules to load.
>
> Forget modules - only the built-in stuff. We cannot be waiting
> indefinitely until someone loads mcelog for decoding.

I added some traces:

$ dmesg | grep mce:
[ 0.033648] mce: mce_register_decode_chain fn=mce_early_notifier+0x0/0x50 pri=6
[ 0.033655] mce: mce_register_decode_chain fn=uc_decode_notifier+0x0/0xd0 pri=5
[ 0.033659] mce: mce_register_decode_chain fn=mce_default_notifier+0x0/0x30 pri=0
[ 4.392631] mce: [Hardware Error]: Machine check events logged
[ 4.393356] mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 0: a000000000004321
[ 4.395352] mce: [Hardware Error]: TSC 0
[ 4.396352] mce: [Hardware Error]: PROCESSOR 0:406f1 TIME 1629743651 SOCKET 0 APIC 0 microcode b000019
[ 15.172861] mce: mce_register_decode_chain fn=dev_mce_log+0x0/0x110 pri=1
[ 15.192101] mce: mcheck_late_init: calling mce_schedule_work()
[ 31.618245] mce: mce_register_decode_chain fn=sbridge_mce_check_error+0x0/0x92 [sb_edac] pri=2

So you are right that mcheck_late_init() is called after dev_mce_log()
is registered. But it seems someone kicks the queue long before that
happens. Probably this:

void mce_log(struct mce *m)
{
if (!mce_gen_pool_add(m))
irq_work_queue(&mce_irq_work);
}

Could we add a flag:

static bool mce_ready_to_rock; // better name needed :-)

Which gets set in mcheck_late_init(). Then mce_log() becomes:

void mce_log(struct mce *m)
{
if (!mce_gen_pool_add(m) && mce_ready_to_rock)
irq_work_queue(&mce_irq_work);
}

-Tony

\
 
 \ /
  Last update: 2021-08-23 20:47    [W:0.049 / U:0.196 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site