proc: Implement /proc/thread-self to point at the directory of the current thread

/proc/thread-self is derived from /proc/self.  /proc/thread-self
points to the directory in proc containing information about the
current thread.

This funtionality has been missing for a long time, and is tricky to
implement in userspace as gettid() is not exported by glibc.  More
importantly this allows fixing defects in /proc/mounts and /proc/net
where in a threaded application today they wind up being empty files
when only the initial pthread has exited, causing problems for other
threads.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/proc/root.c b/fs/proc/root.c
index 5dbadecb234d..48f1c03bc7ed 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -149,6 +149,8 @@ static void proc_kill_sb(struct super_block *sb)
         ns = (struct pid_namespace *)sb->s_fs_info;
         if (ns->proc_self)
                 dput(ns->proc_self);
+        if (ns->proc_thread_self)
+                dput(ns->proc_thread_self);
         kill_anon_super(sb);
         put_pid_ns(ns);
 }
@@ -170,6 +172,7 @@ void __init proc_root_init(void)
                 return;
 
         proc_self_init();
+        proc_thread_self_init();
         proc_symlink("mounts", NULL, "self/mounts");
 
         proc_net_init();