[PATCH 09/10] cfq-iosched: Uses its own open-coded rcu_barrier.

From: Jesper Dangaard Brouer
Date: Tue Jun 23 2009 - 11:32:13 EST

This module cfq-iosched, has discovered the value of waiting for
call_rcu() completion, but its has its own open-coded implementation
of rcu_barrier(), which I don't think is 'strong' enough.

This patch only leaves a comment for the maintainers to consider.

Signed-off-by: Jesper Dangaard Brouer <hawk@xxxxxxx>

block/cfq-iosched.c | 6 ++++++
1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 833ec18..c15555b 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2657,6 +2657,12 @@ static void __exit cfq_exit(void)
* this also protects us from entering cfq_slab_kill() with
* pending RCU callbacks
+ *
+ * hawk@xxxxxxx 2009-06-18: Maintainer please consider using
+ * rcu_barrier() instead of this open-coded wait for
+ * completion implementation. I think it provides a better
+ * guarantee that all CPUs are finished, although
+ * elv_ioc_count_read() do consider all CPUs.
if (elv_ioc_count_read(ioc_count))

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