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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-07-19 15:13:40 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-08-04 08:39:21 -0700
commitaf859beaaba4d57883b08f4acbcb3974bc1f975e (patch)
tree0bff1fa9c43693c9f513daf48197be3627b3301c /kernel/rcu/tree.h
parentcdacbe1f91264687af956e810278030f2ab5a3d0 (diff)
downloadlinux-sh-af859beaaba4d57883b08f4acbcb3974bc1f975e.tar.gz
rcu: Silence lockdep false positive for expedited grace periods
In a CONFIG_PREEMPT=y kernel, synchronize_rcu_expedited() acquires the ->exp_funnel_mutex in rcu_preempt_state, then invokes synchronize_sched_expedited, which acquires the ->exp_funnel_mutex in rcu_sched_state. There can be no deadlock because rcu_preempt_state ->exp_funnel_mutex acquisition always precedes that of rcu_sched_state. But lockdep does not know that, so it gives false-positive splats. This commit therefore associates a separate lock_class_key structure with the rcu_sched_state structure's ->exp_funnel_mutex, allowing lockdep to see the lock ordering, avoiding the false positives. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu/tree.h')
-rw-r--r--kernel/rcu/tree.h8
1 files changed, 8 insertions, 0 deletions
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 80d974df0ea0..0412030ca882 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -70,6 +70,8 @@
# define RCU_NODE_NAME_INIT { "rcu_node_0" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0" }
# define RCU_EXP_NAME_INIT { "rcu_node_exp_0" }
+# define RCU_EXP_SCHED_NAME_INIT \
+ { "rcu_node_exp_sched_0" }
#elif NR_CPUS <= RCU_FANOUT_2
# define RCU_NUM_LVLS 2
# define NUM_RCU_LVL_0 1
@@ -79,6 +81,8 @@
# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1" }
# define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1" }
+# define RCU_EXP_SCHED_NAME_INIT \
+ { "rcu_node_exp_sched_0", "rcu_node_exp_sched_1" }
#elif NR_CPUS <= RCU_FANOUT_3
# define RCU_NUM_LVLS 3
# define NUM_RCU_LVL_0 1
@@ -89,6 +93,8 @@
# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2" }
# define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1", "rcu_node_exp_2" }
+# define RCU_EXP_SCHED_NAME_INIT \
+ { "rcu_node_exp_sched_0", "rcu_node_exp_sched_1", "rcu_node_exp_sched_2" }
#elif NR_CPUS <= RCU_FANOUT_4
# define RCU_NUM_LVLS 4
# define NUM_RCU_LVL_0 1
@@ -100,6 +106,8 @@
# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2", "rcu_node_3" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2", "rcu_node_fqs_3" }
# define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1", "rcu_node_exp_2", "rcu_node_exp_3" }
+# define RCU_EXP_SCHED_NAME_INIT \
+ { "rcu_node_exp_sched_0", "rcu_node_exp_sched_1", "rcu_node_exp_sched_2", "rcu_node_exp_sched_3" }
#else
# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
#endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */