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Commit 0632eb3d authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar
Browse files

rcu: Integrate rcu_dereference_check() message into lockdep 



Make rcu_dereference_check() print the list of held locks in
addition to the stack dump to ease debugging.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1266887105-1528-3-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent c26d34a5

include/linux/lockdep.h

+4 −0
Original line number Diff line number Diff line
@@ -534,4 +534,8 @@ do { \ 
# define might_lock_read(lock) do { } while (0)

#endif



#ifdef CONFIG_PROVE_RCU

extern void lockdep_rcu_dereference(const char *file, const int line);

#endif



#endif /* __LINUX_LOCKDEP_H */

include/linux/rcupdate.h

+2 −2
Original line number Diff line number Diff line
@@ -182,8 +182,8 @@ static inline int rcu_read_lock_sched_held(void) 
 */

#define rcu_dereference_check(p, c) \

	({ \

		if (debug_locks) \

			WARN_ON_ONCE(!(c)); \

		if (debug_locks && !(c)) \

			lockdep_rcu_dereference(__FILE__, __LINE__); \

		rcu_dereference_raw(p); \

	})

kernel/lockdep.c

+18 −0
Original line number Diff line number Diff line
@@ -3809,3 +3809,21 @@ void lockdep_sys_exit(void) 
		lockdep_print_held_locks(curr);

	}

}



void lockdep_rcu_dereference(const char *file, const int line)

{

	struct task_struct *curr = current;



	if (!debug_locks_off())

		return;

	printk("\n==============================================\n");

	printk(  "[ BUG: Unsafe rcu_dereference_check() usage! ]\n");

	printk(  "----------------------------------------------\n");

	printk("%s:%d invoked rcu_dereference_check() without protection!\n",

			file, line);

	printk("\nother info that might help us debug this:\n\n");

	lockdep_print_held_locks(curr);

	printk("\nstack backtrace:\n");

	dump_stack();

}

EXPORT_SYMBOL_GPL(lockdep_rcu_dereference);