linux-kernel - Re: [RFC,PATCH] workqueues: turn queue_work() into the "barrier" for work->func()

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, 11 Nov 2008 22:46:21 +0000
From:	David Howells <dhowells@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	dhowells@...hat.com, Andrew Morton <akpm@...ux-foundation.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Jiri Pirko <jpirko@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC,PATCH] workqueues: turn queue_work() into the "barrier" for work->func()

Oleg Nesterov <oleg@...hat.com> wrote:

> I think the caller of queue_work() has all rights to expect that
> the next invocation of work_func() must see "VAR == 1", but this
> is not true if the work is already pending.

As you said, queue_work() does test_and_set_bit() which implies smp_mb()
either side of the function, so you're half way there, and run_workqueue()
calls spin_unlock_irq() just before calling work_clear_pending()...  So might
it make sense to move the work_clear_pending() into locked section?  Or would
that require an smp_mb__before_clear_bit()?

David
--
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/