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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2009-10-06 21:48:17 -0700
committerIngo Molnar <mingo@elte.hu>2009-10-07 08:11:20 +0200
commite74f4c4564455c91a3b4075bb1721993c2a95dda (patch)
tree213f9df0974c6e1e729de207b2c6dd942a39ba8c /kernel/rcutree_plugin.h
parentd0ec774cb2599c858be9d923bb873cf6697520d8 (diff)
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rcu: Make hot-unplugged CPU relinquish its own RCU callbacks
The current interaction between RCU and CPU hotplug requires that RCU block in CPU notifiers waiting for callbacks to drain. This can be greatly simplified by having each CPU relinquish its own callbacks, and for both _rcu_barrier() and CPU_DEAD notifiers to adopt all callbacks that were previously relinquished. This change also eliminates the possibility of certain types of hangs due to the previous practice of waiting for callbacks to be invoked from within CPU notifiers. If you don't every wait, you cannot hang. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1254890898456-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/rcutree_plugin.h')
-rw-r--r--kernel/rcutree_plugin.h34
1 files changed, 34 insertions, 0 deletions
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 57200fe96d0a..c0cb783aa16a 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -410,6 +410,15 @@ static int rcu_preempt_needs_cpu(int cpu)
return !!per_cpu(rcu_preempt_data, cpu).nxtlist;
}
+/**
+ * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete.
+ */
+void rcu_barrier(void)
+{
+ _rcu_barrier(&rcu_preempt_state, call_rcu);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier);
+
/*
* Initialize preemptable RCU's per-CPU data.
*/
@@ -419,6 +428,14 @@ static void __cpuinit rcu_preempt_init_percpu_data(int cpu)
}
/*
+ * Move preemptable RCU's callbacks to ->orphan_cbs_list.
+ */
+static void rcu_preempt_send_cbs_to_orphanage(void)
+{
+ rcu_send_cbs_to_orphanage(&rcu_preempt_state);
+}
+
+/*
* Initialize preemptable RCU's state structures.
*/
static void __init __rcu_init_preempt(void)
@@ -564,6 +581,16 @@ static int rcu_preempt_needs_cpu(int cpu)
}
/*
+ * Because preemptable RCU does not exist, rcu_barrier() is just
+ * another name for rcu_barrier_sched().
+ */
+void rcu_barrier(void)
+{
+ rcu_barrier_sched();
+}
+EXPORT_SYMBOL_GPL(rcu_barrier);
+
+/*
* Because preemptable RCU does not exist, there is no per-CPU
* data to initialize.
*/
@@ -572,6 +599,13 @@ static void __cpuinit rcu_preempt_init_percpu_data(int cpu)
}
/*
+ * Because there is no preemptable RCU, there are no callbacks to move.
+ */
+static void rcu_preempt_send_cbs_to_orphanage(void)
+{
+}
+
+/*
* Because preemptable RCU does not exist, it need not be initialized.
*/
static void __init __rcu_init_preempt(void)