[lkml]   [2017]   [Apr]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH tip/core/rcu 06/13] hlist_add_tail_rcu disable sparse warning
From: "Michael S. Tsirkin" <>

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 <>
Reviewed-by: Steven Rostedt (VMware) <>
Signed-off-by: Paul E. McKenney <>
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) {
 \ /
  Last update: 2017-04-12 18:59    [W:0.337 / U:9.700 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site