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From: Ian Jackson <Ian.Jackson@eu.citrix.com>
To: Ian Campbell <ian.campbell@citrix.com>
Cc: xen-devel@lists.xenproject.org, Martin Lucina <martin@lucina.net>,
	Wei Liu <wei.liu2@citrix.com>,
	Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Subject: Re: [PATCH] xenconsole: Ensure exclusive access to console using locks
Date: Fri, 24 Jul 2015 14:35:44 +0100	[thread overview]
Message-ID: <21938.16176.972242.374529@mariner.uk.xensource.com> (raw)
In-Reply-To: <1437743460.24746.88.camel@citrix.com>

Ian Campbell writes ("Re: [PATCH] xenconsole: Ensure exclusive access to console using locks"):
> I think the answer is to either not remove the lockfile

That is a bit messy (although not entirely wrong).

> or to do so _before_ dropping the lock, which makes the unlink
> itself the effective unlock point.

This is necessary but not sufficient.  With only that change:

  A  open flock    unlink    close

  B            open               flock  .o{ I have the lock }

  C                      open     flock  .o{ I have the lock }

B is mistaken because it olds an fd onto an unlinked file.

Ian.

  reply	other threads:[~2015-07-24 13:35 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-07-22 17:08 [PATCH] xenconsole: Allow non-interactive use Martin Lucina
2015-07-23  8:48 ` Ian Campbell
2015-07-23 10:53   ` Wei Liu
2015-07-23 15:09   ` Martin Lucina
2015-07-23 15:23     ` Ian Campbell
2015-07-24 11:30       ` [PATCH v2] " Martin Lucina
2015-07-24 13:13         ` Ian Campbell
2015-07-24 11:36       ` [PATCH] " Martin Lucina
2015-07-24 11:44         ` Ian Campbell
2015-07-24 12:51           ` [PATCH] xenconsole: Ensure exclusive access to console using locks Martin Lucina
2015-07-24 13:11             ` Ian Campbell
2015-07-24 13:35               ` Ian Jackson [this message]
2015-07-24 13:40               ` Martin Lucina
2015-07-24 13:54                 ` Ian Campbell
2015-07-24 13:32             ` Ian Jackson
2015-07-24 13:42               ` Martin Lucina
2015-07-24 14:47                 ` [PATCH v2] " Martin Lucina
2015-07-24 15:07                   ` Ian Jackson
2015-07-24 15:29                     ` [PATCH v3] " Martin Lucina
2015-07-24 16:01                       ` Ian Jackson
2015-07-27 12:44                         ` Martin Lucina
2015-07-27 13:29                           ` Wei Liu
2015-07-27 15:14                             ` Ian Campbell
2015-07-24 15:12                   ` [PATCH v2] " Ian Campbell
2015-07-24 13:42               ` [PATCH] " Ian Campbell

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