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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-07-19 22:13:40 (GMT) |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-08-04 15:39:21 (GMT) |
| commit | af859beaaba4d57883b08f4acbcb3974bc1f975e (patch) | |
| tree | 0bff1fa9c43693c9f513daf48197be3627b3301c /kernel/rcu/tree.c | |
| parent | cdacbe1f91264687af956e810278030f2ab5a3d0 (diff) | |
| download | linux-af859beaaba4d57883b08f4acbcb3974bc1f975e.tar.xz | |
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.c')
| -rw-r--r-- | kernel/rcu/tree.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 3af0dee..439112e 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -71,6 +71,7 @@ MODULE_ALIAS("rcutree"); static struct lock_class_key rcu_node_class[RCU_NUM_LVLS]; static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS]; static struct lock_class_key rcu_exp_class[RCU_NUM_LVLS]; +static struct lock_class_key rcu_exp_sched_class[RCU_NUM_LVLS]; /* * In order to export the rcu_state name to the tracing tools, it @@ -4049,6 +4050,7 @@ static void __init rcu_init_one(struct rcu_state *rsp, static const char * const buf[] = RCU_NODE_NAME_INIT; static const char * const fqs[] = RCU_FQS_NAME_INIT; static const char * const exp[] = RCU_EXP_NAME_INIT; + static const char * const exp_sched[] = RCU_EXP_SCHED_NAME_INIT; static u8 fl_mask = 0x1; int levelcnt[RCU_NUM_LVLS]; /* # nodes in each level. */ @@ -4108,8 +4110,14 @@ static void __init rcu_init_one(struct rcu_state *rsp, INIT_LIST_HEAD(&rnp->blkd_tasks); rcu_init_one_nocb(rnp); mutex_init(&rnp->exp_funnel_mutex); - lockdep_set_class_and_name(&rnp->exp_funnel_mutex, - &rcu_exp_class[i], exp[i]); + if (rsp == &rcu_sched_state) + lockdep_set_class_and_name( + &rnp->exp_funnel_mutex, + &rcu_exp_sched_class[i], exp_sched[i]); + else + lockdep_set_class_and_name( + &rnp->exp_funnel_mutex, + &rcu_exp_class[i], exp[i]); } } |