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authorAndrey Vagin <avagin@openvz.org>2015-04-16 12:49:38 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-04-17 09:04:12 -0400
commit6c8c90319c0bb1c9e0b68e721359b89ae4f28465 (patch)
treec144b3bde190f4411d36792fc456571df29c678f /Documentation/filesystems
parent15eb42d674de8da66950f78b5c7202accabe026e (diff)
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')
-rw-r--r--Documentation/filesystems/proc.txt4
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.