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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Harald Arnesen <harald@skogtun.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Giovanni Gherdovich <ggherdovich@suse.cz>
Subject: Re: [BISECTED]: Kernel panic (was: Linux 5.7-rc2)
Date: Tue, 21 Apr 2020 12:03:10 -0700
Message-ID: <CAHk-=wiX+NT2yxtdPszH9U_S96MCNQA56GJFXY45mZc47yG5KQ@mail.gmail.com> (raw)
In-Reply-To: <428bac87-b6dd-0867-c8f8-622cd606de3e@skogtun.org>

On Mon, Apr 20, 2020 at 1:52 AM Harald Arnesen <harald@skogtun.org> 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

  https://lore.kernel.org/lkml/20200416054745.740-1-ggherdovich@suse.cz/

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...

                  Linus

  parent reply index

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] ` <428bac87-b6dd-0867-c8f8-622cd606de3e@skogtun.org>
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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