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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-06-27 09:36:29 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-07-17 14:58:59 -0700
commit704dd435ac7eaefa89fcd82fd2876b8330e00ff3 (patch)
tree7b57a6ab5bed14ddbd1a58ed015c853d3a8b7a6c /kernel/rcu/tree_plugin.h
parent4f525a528b9e75571c6bedc6202beff1ced24c32 (diff)
downloadlinux-sh-704dd435ac7eaefa89fcd82fd2876b8330e00ff3.tar.gz
rcu: Consolidate last open-coded expedited memory barrier
One of the requirements on RCU grace periods is that if there is a causal chain of operations that starts after one grace period and ends before another grace period, then the two grace periods must be serialized. There has been (and might still be) code that relies on this, for example, certain types of reference-counting code that does a call_rcu() within an RCU callback function. This requirement is why there is an smp_mb() at the end of both synchronize_sched_expedited() and synchronize_rcu_expedited(). However, this is the only smp_mb() in these functions, so it would be nicer to consolidate it into rcu_exp_gp_seq_end(). This commit does just that. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu/tree_plugin.h')
-rw-r--r--kernel/rcu/tree_plugin.h1
1 files changed, 0 insertions, 1 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index f0d71449ec0c..27b714601c6e 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -735,7 +735,6 @@ void synchronize_rcu_expedited(void)
/* Clean up and exit. */
rcu_exp_gp_seq_end(rsp);
mutex_unlock(&rnp_unlock->exp_funnel_mutex);
- smp_mb(); /* ensure subsequent action seen after grace period. */
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);