linux-kernel - Re: clocksource: Reduce watchdog readout delay limit to prevent false positives

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Message-ID: <4ef0d4b1-e0e6-44ad-b78f-a643716ed977@paulmck-laptop>
Date: Sat, 20 Dec 2025 08:35:05 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>,
	Daniel J Blueman <daniel@...ra.org>,
	John Stultz <jstultz@...gle.com>, Waiman Long <longman@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Tony Luck <tony.luck@...el.com>, Borislav Petkov <bp@...en8.de>,
	Stephen Boyd <sboyd@...nel.org>,
	Scott Hamilton <scott.hamilton@...den.com>
Subject: Re: clocksource: Reduce watchdog readout delay limit to prevent
 false positives

On Sat, Dec 20, 2025 at 09:38:31AM +0100, Thomas Gleixner wrote:
> On Fri, Dec 19 2025 at 16:18, Paul E. McKenney wrote:
> > One might naively hope that the HPETs in a given system could synchronize
> > themselves so that each CPU could read the HPET nearest it instead of
> > everyone reading CPU 0's HPET.  Or that some other means would allow
> > reasonable access times.  Hey, I can dream, can't I?
> 
> Sounds more like a nightmare TBH.

There are systems that manage to provide reasonable timer access times
and fully synchronized timers, and have been for many decades.

So give me ugly hardware, and I will have at most zero sympathy for
complaints about software that is less than perfectly beautiful.

							Thanx, Paul