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From: tip-bot for Paul E. McKenney on 25 Feb 2010 05:20
Commit-ID: 0632eb3d7563d6a76d49a3860b6352d800c92854
Gitweb: http://git.kernel.org/tip/0632eb3d7563d6a76d49a3860b6352d800c92854
Author: Paul E. McKenney <paulmck(a)linux.vnet.ibm.com>
AuthorDate: Mon, 22 Feb 2010 17:04:47 -0800
Committer: Ingo Molnar <mingo(a)elte.hu>
CommitDate: Thu, 25 Feb 2010 09:41:01 +0100

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: Paul E. McKenney <paulmck(a)linux.vnet.ibm.com>
Cc: laijs(a)cn.fujitsu.com
Cc: dipankar(a)in.ibm.com
Cc: mathieu.desnoyers(a)polymtl.ca
Cc: josh(a)joshtriplett.org
Cc: dvhltc(a)us.ibm.com
Cc: niv(a)us.ibm.com
Cc: peterz(a)infradead.org
Cc: rostedt(a)goodmis.org
Cc: Valdis.Kletnieks(a)vt.edu
Cc: dhowells(a)redhat.com
LKML-Reference: <1266887105-1528-3-git-send-email-paulmck(a)linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo(a)elte.hu>
---
include/linux/lockdep.h | 4 ++++
include/linux/rcupdate.h | 4 ++--
kernel/lockdep.c | 18 ++++++++++++++++++
3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 9ccf0e2..10206a8 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -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 */
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 839d296..1a4de31 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -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); \
})

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index c62ec14..672c436 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -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);
--
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Prev: [tip:perf/core] perf/scripts: Fix bug in Util.pm
Next: [tip:core/rcu] vfs: Abstract rcu_dereference_check for files-fdtable use