lkml.org 
[lkml]   [2015]   [Mar]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 05/10] rcu: Limit rcu_state::levelcnt[] to RCU_NUM_LVLS items
    Date
    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>
    Signed-off-by: Alexander Gordeev <agordeev@redhat.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 dd5ce40..f358a83 100644
    --- a/kernel/rcu/tree.h
    +++ b/kernel/rcu/tree.h
    @@ -421,7 +421,7 @@ 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. */
    --
    1.8.3.1


    \
     
     \ /
      Last update: 2015-03-09 10:01    [W:3.536 / U:1.736 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site