linux-kernel - Re: FUTEX_CMP_REQUEUE

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] [day] [month] [year] [list]

Date:	Sat, 09 Jun 2007 11:01:12 -0700
From:	Ulrich Drepper <drepper@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Pierre Peiffer <pierre.peiffer@...l.net>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Dave Jones"@redhat.com, Ingo Molnar <mingo@...e.hu>
Subject: Re: FUTEX_CMP_REQUEUE_PI is not quite there

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Thomas Gleixner wrote:
> Can you put the binaries somewhere for download please ? 

I was waiting until I could test the current patches.  DaveJ built a
kernel based on -rc4-git3 which I tested.  The results are the same.

I've put a statically linked x86-64 binary at

  http://people.redhat.com/drepper/tst-robustpi7.bz2

Running it produces a backtrace with the 2.6.21-1.3218.fc8 kernel and
the machine dies.

The test case creates a robust, PI mutex.  Five threads then run into a
condvar for this mutex.  The main threads wakes them all with a
broadcast which causes the new requeue_pi code to be used.  The woken
threads then (in pthread_cond_wait) lock the mutex and then kill
themselves while holding the mutex.  This is supposed to have the result
that all but the first thread get EDEADOWNER errors.

Note: the condvar futex is not a PI futex.  It cannot be, the semantics
is different.  This is no locking futex.  The kernel will have to deal
with this.  The requeue operation is meaningless if this is not done
since it's only use is for this situation.

- --
➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.7 (GNU/Linux)

iD8DBQFGauro2ijCOnn/RHQRAluEAKC2rG4DSGjwNkYILzQsMtp7jgcN0QCgh4od
bN8HUrwjg1keVo8DjKTQL6o=
=twSF
-----END PGP SIGNATURE-----
-
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/