linux-kernel - Re: [PATCH 32/35] clockevents: Fix cpu down race for hrtimer based broadcasting

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: <alpine.LFD.2.11.1502231214240.25484@knanqh.ubzr>
Date:	Mon, 23 Feb 2015 12:33:13 -0500 (EST)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	linux-kernel@...r.kernel.org, mingo@...nel.org, rjw@...ysocki.net,
	tglx@...utronix.de, Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Subject: Re: [PATCH 32/35] clockevents: Fix cpu down race for hrtimer based
 broadcasting

On Mon, 23 Feb 2015, Nicolas Pitre wrote:

> On Mon, 23 Feb 2015, Peter Zijlstra wrote:
> 
> > The reported function that fails: bL_switcher_restore_cpus() is called
> > in the error paths of the former and the main path in the latter to make
> > the 'stolen' cpus re-appear.
> > 
> > The patch in question somehow makes that go boom.
> > 
> > 
> > Now what all do you need to do to make it go boom? Just enable/disable
> > the switcher once and it'll explode? Or does it need to do actual
> > switches while it is enabled?
> 
> It gets automatically enabled during boot.  Then several switches are 
> performed while user space is brought up.  If I manually disable it 
> via /sys then it goes boom.

OK. Forget the bL switcher.  I configured it out of my kernel and then 
managed to get the same crash by simply hotplugging out one CPU and 
plugging it back in.

$ echo 0 > /sys/devices/system/cpu/cpu2/online
[CPU2 gone]
$ echo 1 > /sys/devices/system/cpu/cpu2/online
[Boom!]


Nicolas
--
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/