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From: Thomas Gleixner <tglx@linutronix.de>
To: Johannes Berg <johannes@sipsolutions.net>,
	Vincent Whitchurch <vincent.whitchurch@axis.com>
Cc: linux-um@lists.infradead.org, linux-kernel@vger.kernel.org,
	Anna-Maria Gleixner <anna-maria@linutronix.de>,
	Frederic Weisbecker <frederic@kernel.org>
Subject: Re: UML time-travel warning from __run_timers
Date: Sun, 03 Apr 2022 18:18:51 +0200	[thread overview]
Message-ID: <877d86m978.ffs@tglx> (raw)
In-Reply-To: <84f9d627092660c38400b607198c3b83f795be7f.camel@sipsolutions.net>

On Sat, Apr 02 2022 at 16:09, Johannes Berg wrote:
> At init, we get
>
> init_timer_cpu(0) base 0 clk=0xffff8ad0, next_expiry=0x13fff8acf
> init_timer_cpu(0) base 1 clk=0xffff8ad0, next_expiry=0x13fff8acf
>
> which makes sense, jiffies is set up to wrap very quickly after boot.
>
> The warning triggers when we have jiffies=0x13fff9600, so it's just
> after the "next_expiry", so in this code:

which does not make sense. If next_expiry is 0x13fff8acf and jiffies
advanced to 0x13fff9600 when the warning triggered, then either it
missed to expire the timer at 0x13fff8acf or it failed to recalculate
next_expiry.

Could you enable all [hr]timer tracepoints on the kernel command line,
set panic on warn and ftrace_dump_on_oops which should spill out the
tracebuffer on the console and provide the output. That should at least
give us an hint what's going on.

Thanks,

        tglx



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  parent reply	other threads:[~2022-04-03 16:18 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-30 11:01 UML time-travel warning from __run_timers Vincent Whitchurch
2022-03-30 12:33 ` Johannes Berg
2022-04-02 14:09 ` Johannes Berg
2022-04-02 14:17   ` Johannes Berg
2022-04-03 16:18   ` Thomas Gleixner [this message]
2022-04-03 17:13     ` Johannes Berg
2022-04-03 17:19       ` Johannes Berg
2022-04-03 23:23         ` Thomas Gleixner
2022-04-03 19:51       ` Thomas Gleixner
2022-04-04  7:02         ` Johannes Berg
2022-04-04  8:32           ` Thomas Gleixner
2022-04-04  8:37             ` Johannes Berg
2022-04-04 12:17               ` Thomas Gleixner

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