Messages in this thread Patch in this message | | | From | "Paul E. McKenney" <> | Subject | [PATCH tip/core/rcu 06/12] rcu: Limit rcu_state::levelcnt[] to RCU_NUM_LVLS items | Date | Fri, 17 Jul 2015 15:30:57 -0700 |
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From: Alexander Gordeev <agordeev@redhat.com>
Variable rcu_num_lvls is limited by RCU_NUM_LVLS macro. In turn, rcu_state::levelcnt[] array is never accessed beyond rcu_num_lvls. Thus, rcu_state::levelcnt[] is safe to limit to RCU_NUM_LVLS items.
Since rcu_num_lvls could be changed during boot (as result of rcutree.rcu_fanout_leaf kernel parameter update) one might assume a new value could overflow the value of RCU_NUM_LVLS. However, that is not the case, since leaf-level fanout is only permitted to increase, resulting in rcu_num_lvls possibly to decrease.
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Alexander Gordeev <agordeev@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> --- kernel/rcu/tree.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index f1f4784f9107..a6faae53ea8f 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -443,7 +443,7 @@ do { \ struct rcu_state { struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ struct rcu_node *level[RCU_NUM_LVLS]; /* Hierarchy levels. */ - u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */ + u32 levelcnt[RCU_NUM_LVLS]; /* # nodes in each level. */ u8 levelspread[RCU_NUM_LVLS]; /* kids/node in each level. */ u8 flavor_mask; /* bit in flavor mask. */ struct rcu_data __percpu *rda; /* pointer of percu rcu_data. */ -- 1.8.1.5
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