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authorLinus Torvalds <torvalds@linux-foundation.org>2009-04-03 17:34:12 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-03 17:34:12 -0700
commitc7edad5fcb86c4398f9ab2ccea82ddcc067b88af (patch)
tree775469b19ee1c6e5d791b63d318f1bb1a5251888
parentb1dbb67911fecb290db3f566281bcd9ccc9dc6df (diff)
parentf69b17d7e745d8edd7c0d90390cbaa77e63c5ea3 (diff)
Merge branch 'rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: rcu: rcu_barrier VS cpu_hotplug: Ensure callbacks in dead cpu are migrated to online cpu
-rw-r--r--kernel/rcupdate.c44
1 files changed, 44 insertions, 0 deletions
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index cae8a059cf4..2c7b8457d0d 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -122,6 +122,8 @@ static void rcu_barrier_func(void *type)
}
}
+static inline void wait_migrated_callbacks(void);
+
/*
* Orchestrate the specified type of RCU barrier, waiting for all
* RCU callbacks of the specified type to complete.
@@ -147,6 +149,7 @@ static void _rcu_barrier(enum rcu_barrier type)
complete(&rcu_barrier_completion);
wait_for_completion(&rcu_barrier_completion);
mutex_unlock(&rcu_barrier_mutex);
+ wait_migrated_callbacks();
}
/**
@@ -176,9 +179,50 @@ void rcu_barrier_sched(void)
}
EXPORT_SYMBOL_GPL(rcu_barrier_sched);
+static atomic_t rcu_migrate_type_count = ATOMIC_INIT(0);
+static struct rcu_head rcu_migrate_head[3];
+static DECLARE_WAIT_QUEUE_HEAD(rcu_migrate_wq);
+
+static void rcu_migrate_callback(struct rcu_head *notused)
+{
+ if (atomic_dec_and_test(&rcu_migrate_type_count))
+ wake_up(&rcu_migrate_wq);
+}
+
+static inline void wait_migrated_callbacks(void)
+{
+ wait_event(rcu_migrate_wq, !atomic_read(&rcu_migrate_type_count));
+}
+
+static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self,
+ unsigned long action, void *hcpu)
+{
+ if (action == CPU_DYING) {
+ /*
+ * preempt_disable() in on_each_cpu() prevents stop_machine(),
+ * so when "on_each_cpu(rcu_barrier_func, (void *)type, 1);"
+ * returns, all online cpus have queued rcu_barrier_func(),
+ * and the dead cpu(if it exist) queues rcu_migrate_callback()s.
+ *
+ * These callbacks ensure _rcu_barrier() waits for all
+ * RCU callbacks of the specified type to complete.
+ */
+ atomic_set(&rcu_migrate_type_count, 3);
+ call_rcu_bh(rcu_migrate_head, rcu_migrate_callback);
+ call_rcu_sched(rcu_migrate_head + 1, rcu_migrate_callback);
+ call_rcu(rcu_migrate_head + 2, rcu_migrate_callback);
+ } else if (action == CPU_POST_DEAD) {
+ /* rcu_migrate_head is protected by cpu_add_remove_lock */
+ wait_migrated_callbacks();
+ }
+
+ return NOTIFY_OK;
+}
+
void __init rcu_init(void)
{
__rcu_init();
+ hotcpu_notifier(rcu_barrier_cpu_hotplug, 0);
}
void rcu_scheduler_starting(void)