Messages in this thread | | | Date | Mon, 23 Aug 2021 11:45:47 -0700 | From | "Luck, Tony" <> | Subject | Re: [PATCH] x86/mce/dev-mcelog: Call mce_register_decode_chain() much earlier |
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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
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