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| author | Andrey Vagin <avagin@openvz.org> | 2015-04-16 12:49:38 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-04-17 09:04:12 -0400 |
| commit | 6c8c90319c0bb1c9e0b68e721359b89ae4f28465 (patch) | |
| tree | c144b3bde190f4411d36792fc456571df29c678f /Documentation/filesystems/proc.txt | |
| parent | 15eb42d674de8da66950f78b5c7202accabe026e (diff) | |
| download | lwn-6c8c90319c0bb1c9e0b68e721359b89ae4f28465.tar.gz lwn-6c8c90319c0bb1c9e0b68e721359b89ae4f28465.zip | |
proc: show locks in /proc/pid/fdinfo/X
Let's show locks which are associated with a file descriptor in
its fdinfo file.
Currently we don't have a reliable way to determine who holds a lock. We
can find some information in /proc/locks, but PID which is reported there
can be wrong. For example, a process takes a lock, then forks a child and
dies. In this case /proc/locks contains the parent pid, which can be
reused by another process.
$ cat /proc/locks
...
6: FLOCK ADVISORY WRITE 324 00:13:13431 0 EOF
...
$ ps -C rpcbind
PID TTY TIME CMD
332 ? 00:00:00 rpcbind
$ cat /proc/332/fdinfo/4
pos: 0
flags: 0100000
mnt_id: 22
lock: 1: FLOCK ADVISORY WRITE 324 00:13:13431 0 EOF
$ ls -l /proc/332/fd/4
lr-x------ 1 root root 64 Mar 5 14:43 /proc/332/fd/4 -> /run/rpcbind.lock
$ ls -l /proc/324/fd/
total 0
lrwx------ 1 root root 64 Feb 27 14:50 0 -> /dev/pts/0
lrwx------ 1 root root 64 Feb 27 14:50 1 -> /dev/pts/0
lrwx------ 1 root root 64 Feb 27 14:49 2 -> /dev/pts/0
You can see that the process with the 324 pid doesn't hold the lock.
This information is required for proper dumping and restoring file
locks.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Acked-by: Jeff Layton <jlayton@poochiereds.net>
Acked-by: "J. Bruce Fields" <bfields@fieldses.org>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/filesystems/proc.txt')
| -rw-r--r-- | Documentation/filesystems/proc.txt | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 6d370622fdfe..8e36c7e3c345 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -1709,6 +1709,10 @@ A typical output is flags: 0100002 mnt_id: 19 +All locks associated with a file descriptor are shown in its fdinfo too. + +lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF + The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags pair provide additional information particular to the objects they represent. |