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Re: [Qemu-trivial] [Qemu-devel] [PATCH v2] keep the PID file locked for

From: Anthony Liguori
Subject: Re: [Qemu-trivial] [Qemu-devel] [PATCH v2] keep the PID file locked for the lifetime of the process
Date: Fri, 03 Feb 2012 11:21:23 -0600
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20110922 Lightning/1.0b2 Thunderbird/3.1.15

On 01/27/2012 07:34 AM, Laszlo Ersek wrote:
The lockf() call in qemu_create_pidfile() aims at ensuring mutual
exclusion. We shouldn't close the pidfile on success (as introduced by
commit 1bbd1592), because that drops the lock as well [1]:

     "File locks shall be released on first close by the locking process
     of any file descriptor for the file."

Coverity may complain again about the leaked file descriptor; let's
worry about that later.

- add reference to 1bbd1592
- explain the intentional fd leak in the source

[1] http://pubs.opengroup.org/onlinepubs/9699919799/functions/lockf.html

Applied.  Thanks.


Anthony Liguori

Signed-off-by: Laszlo Ersek<address@hidden>
  os-posix.c |    2 +-
  1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/os-posix.c b/os-posix.c
index 5c437ca..e3ed497 100644
--- a/os-posix.c
+++ b/os-posix.c
@@ -348,6 +348,6 @@ int qemu_create_pidfile(const char *filename)
          return -1;

-    close(fd);
+    /* keep pidfile open&  locked forever */
      return 0;

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