Re: [PATCH] x86/mce: Restore MCA polling interval halving

[Nikolay Borisov <nik.borisov@suse.com>]

On 7.04.26 г. 1:49 ч., Borislav Petkov wrote:
> Ok,
> 
> finally. :-\
> 
> Pls run it to make sure it DTRT for you too.
> 
> Thx.
> 
> ---
> From: "Borislav Petkov (AMD)" <bp@alien8.de>
> Date: Mon, 16 Mar 2026 16:12:00 +0100
> Subject: [PATCH] x86/mce: Restore MCA polling interval halving
> 
> RongQing reported that the MCA polling interval doesn't halve when an
> error gets logged. It was traced down to the commit in Fixes: because:
> 
> mce_timer_fn()
> |-> mce_poll_banks()
> |-> machine_check_poll()
> |-> mce_log()
> 
> which will queue the work and return.
> 
> Now, back in mce_timer_fn():
> 
>          /*
>           * Alert userspace if needed. If we logged an MCE, reduce the polling
>           * interval, otherwise increase the polling interval.
>           */
>          if (mce_notify_irq())
> 
> <--- here we haven't ran the notifier chain yet so mce_need_notify is
> not set yet so this won't hit and we won't halve the interval iv.
> 
> Now the notifier chain runs. mce_early_notifier() sets the bit, does
> mce_notify_irq(), that clears the bit and then the notifier chain
> a little later logs the error.
> 
> So this is a silly timing issue.
> 
> But, that's all unnecessary.
> 
> All it needs to happen here is, the "should we notify of a logged MCE"
> mce_notify_irq() asks, should be simply a question to the mce gen pool:
> "Are you empty?"
> 
> And that then turns into a simple yes or no answer and it all
> JustWorks(tm).
> 
> So do that.
> 
> Fixes: 011d82611172 ("RAS: Add a Corrected Errors Collector")
> Reported-by: Li RongQing <lirongqing@baidu.com>
> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
> Link: https://lore.kernel.org/r/20260112082747.2842-1-lirongqing@baidu.com


Much cleaner and simpler,

Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>