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![]() 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> |
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.. | ||
lglock.c | ||
lockdep.c | ||
lockdep_internals.h | ||
lockdep_proc.c | ||
lockdep_states.h | ||
locktorture.c | ||
Makefile | ||
mcs_spinlock.h | ||
mutex-debug.c | ||
mutex-debug.h | ||
mutex.c | ||
mutex.h | ||
osq_lock.c | ||
percpu-rwsem.c | ||
qrwlock.c | ||
rtmutex-debug.c | ||
rtmutex-debug.h | ||
rtmutex-tester.c | ||
rtmutex.c | ||
rtmutex.h | ||
rtmutex_common.h | ||
rwsem-spinlock.c | ||
rwsem-xadd.c | ||
rwsem.c | ||
rwsem.h | ||
semaphore.c | ||
spinlock.c | ||
spinlock_debug.c |