]> git.karo-electronics.de Git - linux-beck.git/commit
pid: fix lockdep deadlock warning due to ucount_lock
authorAndrei Vagin <avagin@openvz.org>
Thu, 5 Jan 2017 03:28:14 +0000 (19:28 -0800)
committerEric W. Biederman <ebiederm@xmission.com>
Tue, 10 Jan 2017 00:34:56 +0000 (13:34 +1300)
commitadd7c65ca426b7a37184dd3d2172394e23d585d6
tree28b08b519540041b06ed0ab0b1c005076b932e8e
parent75422726b0f717d67db3283c2eb5bc14fa2619c5
pid: fix lockdep deadlock warning due to ucount_lock

=========================================================
[ INFO: possible irq lock inversion dependency detected ]
4.10.0-rc2-00024-g4aecec9-dirty #118 Tainted: G        W
---------------------------------------------------------
swapper/1/0 just changed the state of lock:
 (&(&sighand->siglock)->rlock){-.....}, at: [<ffffffffbd0a1bc6>] __lock_task_sighand+0xb6/0x2c0
but this lock took another, HARDIRQ-unsafe lock in the past:
 (ucounts_lock){+.+...}
and interrupts could create inverse lock ordering between them.
other info that might help us debug this:
Chain exists of:                 &(&sighand->siglock)->rlock --> &(&tty->ctrl_lock)->rlock --> ucounts_lock
 Possible interrupt unsafe locking scenario:
       CPU0                    CPU1
       ----                    ----
  lock(ucounts_lock);
                               local_irq_disable();
                               lock(&(&sighand->siglock)->rlock);
                               lock(&(&tty->ctrl_lock)->rlock);
  <Interrupt>
    lock(&(&sighand->siglock)->rlock);

 *** DEADLOCK ***

This patch removes a dependency between rlock and ucount_lock.

Fixes: f333c700c610 ("pidns: Add a limit on the number of pid namespaces")
Cc: stable@vger.kernel.org
Signed-off-by: Andrei Vagin <avagin@openvz.org>
Acked-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
kernel/pid_namespace.c