Messages in this thread Patch in this message | | | From | "Paul E. McKenney" <> | Subject | [PATCH tip/core/urgent 3/5] rcu: leave lockdep enabled after RCU lockdep splat | Date | Wed, 21 Apr 2010 13:02:09 -0700 |
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From: Lai Jiangshan <laijs@cn.fujitsu.com>
There is no need to disable lockdep after an RCU lockdep splat, so remove the debug_lockdeps_off() from lockdep_rcu_dereference(). To avoid repeated lockdep splats, use a static variable in the inlined rcu_dereference_check() and rcu_dereference_protected() macros so that a given instance splats only once, but so that multiple instances can be detected per boot.
Requested-by: Eric Paris <eparis@redhat.com> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Tested-by: Eric Paris <eparis@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> --- include/linux/rcupdate.h | 15 +++++++++++---- kernel/lockdep.c | 2 -- 2 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 07db2fe..ec9ab49 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -190,6 +190,15 @@ static inline int rcu_read_lock_sched_held(void) #ifdef CONFIG_PROVE_RCU +#define __do_rcu_dereference_check(c) \ + do { \ + static bool __warned; \ + if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \ + __warned = true; \ + lockdep_rcu_dereference(__FILE__, __LINE__); \ + } \ + } while (0) + /** * rcu_dereference_check - rcu_dereference with debug checking * @p: The pointer to read, prior to dereferencing @@ -219,8 +228,7 @@ static inline int rcu_read_lock_sched_held(void) */ #define rcu_dereference_check(p, c) \ ({ \ - if (debug_lockdep_rcu_enabled() && !(c)) \ - lockdep_rcu_dereference(__FILE__, __LINE__); \ + __do_rcu_dereference_check(c); \ rcu_dereference_raw(p); \ }) @@ -237,8 +245,7 @@ static inline int rcu_read_lock_sched_held(void) */ #define rcu_dereference_protected(p, c) \ ({ \ - if (debug_lockdep_rcu_enabled() && !(c)) \ - lockdep_rcu_dereference(__FILE__, __LINE__); \ + __do_rcu_dereference_check(c); \ (p); \ }) diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 2594e1c..03dd1fa 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -3801,8 +3801,6 @@ void lockdep_rcu_dereference(const char *file, const int line) { struct task_struct *curr = current; - if (!debug_locks_off()) - return; printk("\n===================================================\n"); printk( "[ INFO: suspicious rcu_dereference_check() usage. ]\n"); printk( "---------------------------------------------------\n"); -- 1.7.0
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