Commit-ID: dd7c4d89730a1be2c1d361a8ae1f0fe9465ccf9c
Gitweb: http://git.kernel.org/tip/dd7c4d89730a1be2c1d361a8ae1f0fe9465ccf9c
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Fri, 27 Aug 2010 10:51:17 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Fri, 27 Aug 2010 10:51:17 -0700
rcu: performance fixes to TINY_PREEMPT_RCU callback checking
This commit tightens up checks in rcu_preempt_check_callbacks() to avoid
unnecessary special handling at rcu_read_unlock() time.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcutiny_plugin.h | 12 ++++++++----
1 files changed, 8 insertions(+), 4 deletions(-)
diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
index c5bea11..6ceca4f 100644
--- a/kernel/rcutiny_plugin.h
+++ b/kernel/rcutiny_plugin.h
@@ -72,7 +72,7 @@ static void rcu_report_exp_done(void);
/*
* Return true if the CPU has not yet responded to the current grace period.
*/
-static int rcu_cpu_cur_gp(void)
+static int rcu_cpu_blocking_cur_gp(void)
{
return rcu_preempt_ctrlblk.gpcpu != rcu_preempt_ctrlblk.gpnum;
}
@@ -229,7 +229,7 @@ void rcu_preempt_note_context_switch(void)
* cannot end.
*/
list_add(&t->rcu_node_entry, &rcu_preempt_ctrlblk.blkd_tasks);
- if (rcu_cpu_cur_gp())
+ if (rcu_cpu_blocking_cur_gp())
rcu_preempt_ctrlblk.gp_tasks = &t->rcu_node_entry;
}
@@ -368,12 +368,16 @@ static void rcu_preempt_check_callbacks(void)
{
struct task_struct *t = current;
- if (!rcu_preempt_running_reader() && rcu_preempt_gp_in_progress())
+ if (rcu_preempt_gp_in_progress() &&
+ (!rcu_preempt_running_reader() ||
+ !rcu_cpu_blocking_cur_gp()))
rcu_preempt_cpu_qs();
if (&rcu_preempt_ctrlblk.rcb.rcucblist !=
rcu_preempt_ctrlblk.rcb.donetail)
raise_softirq(RCU_SOFTIRQ);
- if (rcu_preempt_gp_in_progress() && rcu_preempt_running_reader())
+ if (rcu_preempt_gp_in_progress() &&
+ rcu_cpu_blocking_cur_gp() &&
+ rcu_preempt_running_reader())
t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS;
}
--
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