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authorPaul E. McKenney <paul.mckenney@linaro.org>2011-08-04 07:55:34 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2011-09-28 21:38:39 -0700
commit82e78d80fc392ac7e98326bc8beeb8a679913ffd (patch)
tree4999d3c03ed711056474c3a31512e7d3cf253b87
parent5c51dd7349d4bb26f845f17f85daa168f5fa03f2 (diff)
rcu: Simplify unboosting checks
Commit 7765be (Fix RCU_BOOST race handling current->rcu_read_unlock_special) introduced a new ->rcu_boosted field in the task structure. This is redundant because the existing ->rcu_boost_mutex will be non-NULL at any time that ->rcu_boosted is nonzero. Therefore, this commit removes ->rcu_boosted and tests ->rcu_boost_mutex instead. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
-rw-r--r--include/linux/sched.h3
-rw-r--r--kernel/rcutree_plugin.h20
2 files changed, 10 insertions, 13 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6ee91e20353..acca4356080 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1259,9 +1259,6 @@ struct task_struct {
#ifdef CONFIG_PREEMPT_RCU
int rcu_read_lock_nesting;
char rcu_read_unlock_special;
-#if defined(CONFIG_RCU_BOOST) && defined(CONFIG_TREE_PREEMPT_RCU)
- int rcu_boosted;
-#endif /* #if defined(CONFIG_RCU_BOOST) && defined(CONFIG_TREE_PREEMPT_RCU) */
struct list_head rcu_node_entry;
#endif /* #ifdef CONFIG_PREEMPT_RCU */
#ifdef CONFIG_TREE_PREEMPT_RCU
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index ed70f6bf4c3..eeb38ee8ebb 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -306,6 +306,9 @@ static noinline void rcu_read_unlock_special(struct task_struct *t)
int empty_exp;
unsigned long flags;
struct list_head *np;
+#ifdef CONFIG_RCU_BOOST
+ struct rt_mutex *rbmp = NULL;
+#endif /* #ifdef CONFIG_RCU_BOOST */
struct rcu_node *rnp;
int special;
@@ -351,6 +354,7 @@ static noinline void rcu_read_unlock_special(struct task_struct *t)
smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */
np = rcu_next_node_entry(t, rnp);
list_del_init(&t->rcu_node_entry);
+ t->rcu_blocked_node = NULL;
trace_rcu_unlock_preempted_task("rcu_preempt",
rnp->gpnum, t->pid);
if (&t->rcu_node_entry == rnp->gp_tasks)
@@ -360,13 +364,12 @@ static noinline void rcu_read_unlock_special(struct task_struct *t)
#ifdef CONFIG_RCU_BOOST
if (&t->rcu_node_entry == rnp->boost_tasks)
rnp->boost_tasks = np;
- /* Snapshot and clear ->rcu_boosted with rcu_node lock held. */
- if (t->rcu_boosted) {
- special |= RCU_READ_UNLOCK_BOOSTED;
- t->rcu_boosted = 0;
+ /* Snapshot/clear ->rcu_boost_mutex with rcu_node lock held. */
+ if (t->rcu_boost_mutex) {
+ rbmp = t->rcu_boost_mutex;
+ t->rcu_boost_mutex = NULL;
}
#endif /* #ifdef CONFIG_RCU_BOOST */
- t->rcu_blocked_node = NULL;
/*
* If this was the last task on the current list, and if
@@ -387,10 +390,8 @@ static noinline void rcu_read_unlock_special(struct task_struct *t)
#ifdef CONFIG_RCU_BOOST
/* Unboost if we were boosted. */
- if (special & RCU_READ_UNLOCK_BOOSTED) {
- rt_mutex_unlock(t->rcu_boost_mutex);
- t->rcu_boost_mutex = NULL;
- }
+ if (rbmp)
+ rt_mutex_unlock(rbmp);
#endif /* #ifdef CONFIG_RCU_BOOST */
/*
@@ -1206,7 +1207,6 @@ static int rcu_boost(struct rcu_node *rnp)
t = container_of(tb, struct task_struct, rcu_node_entry);
rt_mutex_init_proxy_locked(&mtx, t);
t->rcu_boost_mutex = &mtx;
- t->rcu_boosted = 1;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
rt_mutex_lock(&mtx); /* Side effect: boosts task t's priority. */
rt_mutex_unlock(&mtx); /* Keep lockdep happy. */