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]
Date:	Mon, 5 Jan 2009 18:21:36 -0800
From:	"john stultz-lkml" <johnstul.lkml@...il.com>
To:	"Chris Adams" <cmadams@...aay.net>
Cc:	"Linas Vepstas" <linasvepstas@...il.com>,
	linux-kernel@...r.kernel.org,
	"Thomas Gleixner" <tglx@...utronix.de>
Subject: Re: Bug: Status/Summary of slashdot leap-second crash on new years 2008-2009

On Fri, Jan 2, 2009 at 4:21 PM, Chris Adams <cmadams@...aay.net> wrote:
> Once upon a time, Linas Vepstas <linasvepstas@...il.com> said:
>> Below follows a summary of the reported crashes. I'm ignoring the
>> zillions of "mine didn't crash" reports, or the "you're a paranoid
>> conspiracy theorist, its random chance" reports.
>
> I have reproduced this and got a stack trace (this is with Fedora 8 and
> kernel kernel-2.6.26.6-49.fc8.x86_64):
>
[snip]
> Basically (to my untrained eye), the leap second code is called from the
> timer interrupt handler, which holds xtime_lock.  The leap second code
> does a printk to notify about the leap second.  The printk code tries to
> wake up klogd (I assume to prioritize kernel messages), and (under some
> conditions), the scheduler attempts to get the current time, which tries
> to get xtime_lock => deadlock.

This analysis looks correct to me.

Grrrr. This has bit us a few times since the "no printk while holding
the xtime lock" restriction was added.

Thomas: Do you think this warrents adding a check to the printk path
to make sure the xtime lock isn't held? This way we can at least get a
warning when someone accidentally adds a printk or calls a function
that does while holding the xtime_lock.

thanks
-john
--
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/

Powered by blists - more mailing lists