linux-kernel - Re: [PATCH] workaround minor lockdep bug triggered by mm_take_all

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:	Tue, 05 Aug 2008 05:02:07 -0700
From:	Roland Dreier <rdreier@...co.com>
To:	Andrea Arcangeli <andrea@...ranet.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Dave Jones <davej@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Miller <davem@...emloft.net>, jeremy@...p.org,
	hugh@...itas.com, mingo@...e.hu, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, arjan <arjan@...radead.org>
Subject: Re: [PATCH] workaround minor lockdep bug triggered by mm_take_all_locks

 > Let's focus on check_deadlock->print_deadlock_bug and somebody who's
 > not beyond the point please explain what print_deadlock_bug reports
 > that does not actually occur and why it's a good idea to change the
 > common code to accommodate for its false positives instead of getting
 > rid of it for good.

check_deadlock operates on classes of locks, so it can warn about
potential deadlocks, eg if we have

	foo(obj1, obj2)
	{
		lock(obj1);
		lock(obj2);
		...

then foo(obj, obj); is a deadlock but lockdep can warn about foo(obj,
different_obj) without triggering the deadlock in reality.  Of course
this leads to false positives, and we sometimes have to change correct
code to help lockdep, but usually such rewriting leads to simpler
clearer better locking anyway.

 - R.
--
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/