linux-kernel - Re: kernel/relay.c: a strange usage of delayed

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:	Fri, 04 May 2007 00:42:30 -0500
From:	Tom Zanussi <zanussi@...ibm.com>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Karim Yaghmour <karim@...rsys.com>,
	linux-kernel@...r.kernel.org
Subject: Re: kernel/relay.c: a strange usage of delayed_work

On Fri, 2007-05-04 at 01:38 +0400, Oleg Nesterov wrote:
> relay_switch_subbuf() does schedule_delayed_work(&buf->wake_readers, 1),
> wakeup_readers() only does wake_up_interruptible() and nothing more.
> 
> Why can't we use a plain timer for this?
> 
> In any case, this "wake_up ->read_wait after a minimal possible delay"
> looks somewhat strange to me, could you explain? just curious.
> 

The reason it's done that way is that if the event that causes the
relay_switch_subbuf() happens to be an event logged from schedule(), and
we directly call wake_up_interruptible() at that point, we lock up the
machine because it ends up back in schedule().  Deferring it avoids the
problem.

I don't see any problem with using a plain timer instead - I'll work up
a patch to make that change.

Tom



-
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/