linux-kernel - Re: [PATCH] x86/mce: Fix timer interval adjustment after logging a MCE event

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Message-ID: <aWbjkAPX9a9ZlJGN@agluck-desk3>
Date: Tue, 13 Jan 2026 16:30:08 -0800
From: "Luck, Tony" <tony.luck@...el.com>
To: Borislav Petkov <bp@...en8.de>
CC: "Li, Rongqing" <lirongqing@...du.com>, Nikolay Borisov
	<nik.borisov@...e.com>, Thomas Gleixner <tglx@...nel.org>, Ingo Molnar
	<mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>,
	"x86@...nel.org" <x86@...nel.org>, "H . Peter Anvin" <hpa@...or.com>, "Yazen
 Ghannam" <yazen.ghannam@....com>, "Zhuo, Qiuxu" <qiuxu.zhuo@...el.com>,
	Avadhut Naik <avadhut.naik@....com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-edac@...r.kernel.org"
	<linux-edac@...r.kernel.org>
Subject: Re: [PATCH] x86/mce: Fix timer interval adjustment after logging a
 MCE event

On Tue, Jan 13, 2026 at 11:41:52PM +0100, Borislav Petkov wrote:
> On Tue, Jan 13, 2026 at 10:31:58PM +0100, Borislav Petkov wrote:
> > Ufff, how silly and overengineered we've made it. I need to think about
> > a cleaner solution tomorrow...
> 
> One idea I just thought of:
> 
> those two steps:
> 
> 1. setting mce_need_notify, and
> 
> 2.  testing and clearing it
> 
> are basically logically a one query: do we have logged errors, or, IOW, is the
> gen pool not empty?
> 
> IOW, this below.
> 
> That'll get rid of that gunk of when should we test and when set and will
> JustWork(tm) for what we want it to do.
> 
> But let's see how it all really works tomorrow...
> 
> diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
> index 34440021e8cf..c378d4d450b6 100644
> --- a/arch/x86/kernel/cpu/mce/core.c
> +++ b/arch/x86/kernel/cpu/mce/core.c
> @@ -595,7 +595,7 @@ static bool mce_notify_irq(void)
>  	/* Not more than two messages every minute */
>  	static DEFINE_RATELIMIT_STATE(ratelimit, 60*HZ, 2);
>  
> -	if (test_and_clear_bit(0, &mce_need_notify)) {
> +	if (!mce_gen_pool_empty()) {
>  		mce_work_trigger();
>  
>  		if (__ratelimit(&ratelimit))
> @@ -618,10 +618,6 @@ static int mce_early_notifier(struct notifier_block *nb, unsigned long val,
>  	/* Emit the trace record: */
>  	trace_mce_record(err);
>  
> -	set_bit(0, &mce_need_notify);
> -
> -	mce_notify_irq();
> -
>  	return NOTIFY_DONE;
>  }
>  

Seems to work (though you've deleted all the places where mce_need_notify
is used, so you can also delete the declaration.

@@ -90,7 +90,6 @@ struct mca_config mca_cfg __read_mostly = {
 };

 static DEFINE_PER_CPU(struct mce_hw_err, hw_errs_seen);
-static unsigned long mce_need_notify;

 /*
  * MCA banks polled by the period polling timer for corrected events.


I see time delta between logs reducing while I'm injecting errors.

When I pause injection for several minutes, and then restart I see the
interval went back up again.

-Tony