From: Tim Hockin <thockin@google.com>
Date: Sat, 21 Jul 2007 15:10:35 +0000 (+0200)
Subject: x86_64: O_EXCL on /dev/mcelog
X-Git-Tag: v2.6.23-rc1~104
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f528e7ba28492e363a64c80c414ded4cadf48f89;p=pandora-kernel.git

x86_64: O_EXCL on /dev/mcelog

Background:
 /dev/mcelog is a clear-on-read interface.  It is currently possible for
 multiple users to open and read() the device.  Users are protected from
 each other during any one read, but not across reads.

Description:
 This patch adds support for O_EXCL to /dev/mcelog.  If a user opens the
 device with O_EXCL, no other user may open the device (EBUSY).  Likewise,
 any user that tries to open the device with O_EXCL while another user has
 the device will fail (EBUSY).

Result:
 Applications can get exclusive access to /dev/mcelog.  Applications that
 do not care will be unchanged.

Alternatives:
 A simpler choice would be to only allow one open() at all, regardless of
 O_EXCL.

Testing:
 I wrote an application that opens /dev/mcelog with O_EXCL and observed
 that any other app that tried to open /dev/mcelog would fail until the
 exclusive app had closed the device.

Caveats:
 None.

Signed-off-by: Tim Hockin <thockin@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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