Commit-ID: b6a932d1d9840727eee619d455bdeeedaa205be9
Gitweb: http://git.kernel.org/tip/b6a932d1d9840727eee619d455bdeeedaa205be9
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Fri, 31 Oct 2014 12:05:04 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Tue, 6 Jan 2015 11:02:43 -0800
rcu: Make rcu_read_unlock_special() propagate ->qsmaskinit bit clearing
This commit causes rcu_read_unlock_special() to propagate ->qsmaskinit
bit clearing up the rcu_node tree once a given rcu_node structure's
blkd_tasks list becomes empty. This is the final commit in preparation
for the rework of RCU priority boosting: It enables preempted tasks to
remain queued on their rcu_node structure even after all of that rcu_node
structure's CPUs have gone offline.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tree.c | 4 ++++
kernel/rcu/tree_plugin.h | 16 +++++++++++++---
2 files changed, 17 insertions(+), 3 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 75c6b33..6625a1b 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2329,6 +2329,10 @@ static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
{
}
+static void __maybe_unused rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)
+{
+}
+
static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
{
}
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index d044b9c..8a2b841 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -322,9 +322,10 @@ static bool rcu_preempt_has_tasks(struct rcu_node *rnp)
*/
void rcu_read_unlock_special(struct task_struct *t)
{
- int empty_exp;
- int empty_norm;
- int empty_exp_now;
+ bool empty;
+ bool empty_exp;
+ bool empty_norm;
+ bool empty_exp_now;
unsigned long flags;
struct list_head *np;
#ifdef CONFIG_RCU_BOOST
@@ -376,6 +377,7 @@ void rcu_read_unlock_special(struct task_struct *t)
break;
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
}
+ empty = !rcu_preempt_has_tasks(rnp);
empty_norm = !rcu_preempt_blocked_readers_cgp(rnp);
empty_exp = !rcu_preempted_readers_exp(rnp);
smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */
@@ -396,6 +398,14 @@ void rcu_read_unlock_special(struct task_struct *t)
#endif /* #ifdef CONFIG_RCU_BOOST */
/*
+ * If this was the last task on the list, go see if we
+ * need to propagate ->qsmaskinit bit clearing up the
+ * rcu_node tree.
+ */
+ if (!empty && !rcu_preempt_has_tasks(rnp))
+ rcu_cleanup_dead_rnp(rnp);
+
+ /*
* If this was the last task on the current list, and if
* we aren't waiting on any CPUs, report the quiescent state.
* Note that rcu_report_unblock_qs_rnp() releases rnp->lock,
--
To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
|