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| author | Peter Zijlstra <peterz@infradead.org> | 2015-04-15 17:11:57 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-04-17 09:42:14 +0200 |
| commit | d7bc3197b41e0a1af6677e83f8736e93a1575ce0 (patch) | |
| tree | 8b9dbb106e7c287182b3812c0469a1fea8e46c95 /kernel/user_namespace.c | |
| parent | Merge branch 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kerne... (diff) | |
| download | linux-d7bc3197b41e0a1af6677e83f8736e93a1575ce0.tar.xz linux-d7bc3197b41e0a1af6677e83f8736e93a1575ce0.zip | |
lockdep: Make print_lock() robust against concurrent release
During sysrq's show-held-locks command it is possible that
hlock_class() returns NULL for a given lock. The result is then (after
the warning):
|BUG: unable to handle kernel NULL pointer dereference at 0000001c
|IP: [<c1088145>] get_usage_chars+0x5/0x100
|Call Trace:
| [<c1088263>] print_lock_name+0x23/0x60
| [<c1576b57>] print_lock+0x5d/0x7e
| [<c1088314>] lockdep_print_held_locks+0x74/0xe0
| [<c1088652>] debug_show_all_locks+0x132/0x1b0
| [<c1315c48>] sysrq_handle_showlocks+0x8/0x10
This *might* happen because the thread on the other CPU drops the lock
after we are looking ->lockdep_depth and ->held_locks points no longer
to a lock that is held.
The fix here is to simply ignore it and continue.
Reported-by: Andreas Messerschmid <andreas@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/user_namespace.c')
0 files changed, 0 insertions, 0 deletions