linux-kernel - Re: Severe reproducible nouveau breakage in 2.6.36 (and maybe .35)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <AANLkTimcEiBJtWx2tA=dqm6881g0B7NomXFsZauzfgy8@mail.gmail.com>
Date:	Wed, 10 Nov 2010 15:06:07 -0500
From:	Andrew Lutomirski <luto@....edu>
To:	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	Ben Skeggs <bskeggs@...hat.com>
Subject: Re: Severe reproducible nouveau breakage in 2.6.36 (and maybe .35)

On Wed, Nov 10, 2010 at 2:28 PM, Andrew Lutomirski <andy@...o.us> wrote:
> Hi all-
>
> Somewhere between 2.6.34-fedora-whatever and 2.6.36, Nouveau became
> extremely broken on my hardware.  It appears to be triggered by a bug
> in my monitor (HP LP2475w), which causes the monitor to disappear from
> DVI when it goes to sleep.  Every time the console blanks (in X or
> otherwise AFAICT) the system crashes oddly but unrecoverably.  This is
> 100% reproducible by Ctrl-Alt-F2 followed by 'echo 1
>>/sys/class/graphics/fb0/blank' *from SSH* and waiting a few seconds
> for the monitor to go to sleep, but it also happens if I just walk
> away from the computer long enough for it to blank itself.  This is
> present on F14's kernel and on 2.6.36 from kernel.org.  This may or
> may not be related to the unreproducible crashes that I used to get
> rarely on 2.6.34.

>
> The best hint I have is from this patch (sorry for whitespace damage):
>

>
> which spews "nv50 got hpd irq" once the display blanks.

I tracked it down.  The interrupt code in 2.6.36 is totally broken ---
it acknowledges the interrupt *in the bottom half*.  This might work
by accident if the bottom half gets queued on a different CPU, but
something probably changed (concurrency-managed workqueues?) that make
the BH end up on the same cpu.  So the cpu starves the BH and there
goes a cpu.

Then the clocksource watchdog hits and takes the whole system down
when it calls stop_machine, which also gets starved on that cpu.

Patch coming.

--Andy
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/