[tip:core/urgent] rcu: Add control variables to lockdep_rcu_dereference() diagnostics

From: tip-bot for Paul E. McKenney
Date: Thu Mar 04 2010 - 11:32:45 EST

Commit-ID: cc5b83a9f884fe8722a275069a5a6fde39988455
Gitweb: http://git.kernel.org/tip/cc5b83a9f884fe8722a275069a5a6fde39988455
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Wed, 3 Mar 2010 07:46:59 -0800
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Thu, 4 Mar 2010 12:07:32 +0100

rcu: Add control variables to lockdep_rcu_dereference() diagnostics

Add the values of rcu_scheduler_active() and debug_locks() to
the lockdep_rcu_dereference() output to help diagnose RCU
lockdep splats that occur shortly after the scheduler starts.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: laijs@xxxxxxxxxxxxxx
Cc: dipankar@xxxxxxxxxx
Cc: mathieu.desnoyers@xxxxxxxxxx
Cc: josh@xxxxxxxxxxxxxxxx
Cc: dvhltc@xxxxxxxxxx
Cc: niv@xxxxxxxxxx
Cc: peterz@xxxxxxxxxxxxx
Cc: rostedt@xxxxxxxxxxx
Cc: Valdis.Kletnieks@xxxxxx
Cc: dhowells@xxxxxxxxxx
LKML-Reference: <1267631219-8713-4-git-send-email-paulmck@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
kernel/lockdep.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 0c30d04..681bc2e 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -3822,6 +3822,7 @@ void lockdep_rcu_dereference(const char *file, const int line)
printk("%s:%d invoked rcu_dereference_check() without protection!\n",
file, line);
printk("\nother info that might help us debug this:\n\n");
+ printk("\nrcu_scheduler_active = %d, debug_locks = %d\n", rcu_scheduler_active, debug_locks);
printk("\nstack backtrace:\n");
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