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authorJens Axboe <jaxboe@fusionio.com>2011-04-19 11:10:35 +0400
committerJens Axboe <jaxboe@fusionio.com>2011-04-19 11:10:35 +0400
commit5f45c69589b7d2953584e6cd0b31e35dbe960ad0 (patch)
tree7f920cebcbbe6a1435975e355cee15289ddbc428 /block
parentbd900d4580107c899d43b262fbbd995f11097a43 (diff)
downloadlinux-5f45c69589b7d2953584e6cd0b31e35dbe960ad0.tar.xz
cfq-iosched: read_lock() does not always imply rcu_read_lock()
For some configurations of CONFIG_PREEMPT that is not true. So get rid of __call_for_each_cic() and always uses the explicitly rcu_read_lock() protected call_for_each_cic() instead. This fixes a potential bug related to IO scheduler removal or online switching. Thanks to Paul McKenney for clarifying this. Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'block')
-rw-r--r--block/cfq-iosched.c20
1 files changed, 6 insertions, 14 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 46b0a1d1d925..5b52011e3a40 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2582,28 +2582,20 @@ static void cfq_put_queue(struct cfq_queue *cfqq)
}
/*
- * Must always be called with the rcu_read_lock() held
+ * Call func for each cic attached to this ioc.
*/
static void
-__call_for_each_cic(struct io_context *ioc,
- void (*func)(struct io_context *, struct cfq_io_context *))
+call_for_each_cic(struct io_context *ioc,
+ void (*func)(struct io_context *, struct cfq_io_context *))
{
struct cfq_io_context *cic;
struct hlist_node *n;
+ rcu_read_lock();
+
hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
func(ioc, cic);
-}
-/*
- * Call func for each cic attached to this ioc.
- */
-static void
-call_for_each_cic(struct io_context *ioc,
- void (*func)(struct io_context *, struct cfq_io_context *))
-{
- rcu_read_lock();
- __call_for_each_cic(ioc, func);
rcu_read_unlock();
}
@@ -2664,7 +2656,7 @@ static void cfq_free_io_context(struct io_context *ioc)
* should be ok to iterate over the known list, we will see all cic's
* since no new ones are added.
*/
- __call_for_each_cic(ioc, cic_free_func);
+ call_for_each_cic(ioc, cic_free_func);
}
static void cfq_put_cooperator(struct cfq_queue *cfqq)