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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-11-29 13:49:00 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2013-01-08 14:15:25 -0800
commit4930521ae10fd28ebc713107fd243c8044a95415 (patch)
tree16b199df6f2bd65a9915ac63e29c6b0f8584097d
parent1bdc2b7d243dc8b9aadfc8002a69cf911e9e3e72 (diff)
downloadlinux-4930521ae10fd28ebc713107fd243c8044a95415.tar.bz2
rcu: Silence compiler array out-of-bounds false positive
It turns out that gcc 4.8 warns on array indexes being out of bounds unless it can prove otherwise. It gives this warning on some RCU initialization code. Because this is far from any fastpath, add an explicit check for array bounds and panic if so. This gives the compiler enough information to figure out that the array index is never out of bounds. However, if a similar false positive occurs on a fastpath, it will probably be necessary to tell the compiler to keep its array-index anxieties to itself. ;-) Markus Trippelsdorf <markus@trippelsdorf.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
-rw-r--r--kernel/rcutree.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index d145796bd61f..e0d98157fbea 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -2938,6 +2938,10 @@ static void __init rcu_init_one(struct rcu_state *rsp,
BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
+ /* Silence gcc 4.8 warning about array index out of range. */
+ if (rcu_num_lvls > RCU_NUM_LVLS)
+ panic("rcu_init_one: rcu_num_lvls overflow");
+
/* Initialize the level-tracking arrays. */
for (i = 0; i < rcu_num_lvls; i++)