| From | "Paul E. McKenney" <> | Subject | [PATCH v2 tip/core/rcu 06/11] hlist_add_tail_rcu disable sparse warning | Date | Mon, 17 Apr 2017 16:28:53 -0700 |
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From: "Michael S. Tsirkin" <mst@redhat.com>
sparse is unhappy about this code in hlist_add_tail_rcu:
struct hlist_node *i, *last = NULL;
for (i = hlist_first_rcu(h); i; i = hlist_next_rcu(i)) last = i;
This is because hlist_next_rcu and hlist_next_rcu return __rcu pointers.
It's a false positive - it's a write side primitive and so does not need to be called in a read side critical section.
The following trivial patch disables the warning without changing the behaviour in any way.
Note: __hlist_for_each_rcu would also remove the warning but it would be confusing since it calls rcu_derefence and is designed to run in the rcu read side critical section.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> --- include/linux/rculist.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/include/linux/rculist.h b/include/linux/rculist.h index 4f7a9561b8c4..b1fd8bf85fdc 100644 --- a/include/linux/rculist.h +++ b/include/linux/rculist.h @@ -509,7 +509,8 @@ static inline void hlist_add_tail_rcu(struct hlist_node *n, { struct hlist_node *i, *last = NULL; - for (i = hlist_first_rcu(h); i; i = hlist_next_rcu(i)) + /* Note: write side code, so rcu accessors are not needed. */ + for (i = h->first; i; i = i->next) last = i; if (last) { -- 2.5.2
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