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From: Linus Torvalds <>
To: Harald Arnesen <>,
	Peter Zijlstra <>,
	Ingo Molnar <>,
	"Rafael J. Wysocki" <>
Cc: Linux Kernel Mailing List <>,
	Giovanni Gherdovich <>
Subject: Re: [BISECTED]: Kernel panic (was: Linux 5.7-rc2)
Date: Tue, 21 Apr 2020 12:03:10 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Mon, Apr 20, 2020 at 1:52 AM Harald Arnesen <> wrote:
> Neither rc1 nor rc2 will boot on my laptop. The attached picture is all
> I have been able to capture.

I know you saw the reply about this probably being fixed by

but it would be lovely if you could actually verify that that series
of four patches does indeed fix it for you.

Your oops is on that divide instruction:

        freq_scale = div64_u64(acnt, mcnt);

and while we had a check for mcnt not being zero earlier, we did

        mcnt *= arch_max_freq_ratio;

after that check. I could see it becoming zero either due to an
overflow, or due to arch_max_freq_ratio being 0.

I think the first commit in that series is supposed to fix that
arch_max_freq_ratio being 0 case, but it still feels like the code
that does the divide is checking for zero in the wrong place...


  parent reply	other threads:[~2020-04-21 19:03 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-19 21:58 Linux 5.7-rc2 Linus Torvalds
     [not found] ` <>
2020-04-21 19:03   ` Linus Torvalds [this message]
2020-04-21 21:23     ` [BISECTED]: Kernel panic (was: Linux 5.7-rc2) Peter Zijlstra
2020-04-21 21:30       ` Linus Torvalds
2020-04-21 21:41         ` Peter Zijlstra
2020-04-22  9:02       ` Giovanni Gherdovich
2020-04-22  9:37         ` Harald Arnesen
2020-04-22 10:22           ` Harald Arnesen
2020-04-22 11:01             ` Giovanni Gherdovich
2020-04-22 14:12         ` Dave Kleikamp
2020-04-22 14:49           ` Giovanni Gherdovich
2020-04-22  9:32     ` Harald Arnesen

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