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
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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>

path: root/str.h

#ifndef STR_H
#define STR_H

#include "built_in.h"

extern size_t strlcpy(char *dest, const char *src, size_t size);
extern int slprintf(char *dst, size_t size, const char *fmt, ...)  __check_format_printf(3, 4);
extern int slprintf_nocheck(char *dst, size_t size, const char *fmt, ...);
extern char *strtrim_right(char *p, char c);
extern noinline void *xmemset(void *s, int c, size_t n);

#endif /* STR_H */