From: Alexander Gordeev <agordeev@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: Alexander Gordeev <agordeev@redhat.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH 05/10] rcu: Limit rcu_state::levelcnt[] to RCU_NUM_LVLS items
Date: Mon, 9 Mar 2015 09:34:09 +0100 [thread overview]
Message-ID: <8c4fac4157014a0dcd3a22b60f0e4aaf03e28e50.1425889432.git.agordeev@redhat.com> (raw)
In-Reply-To: <cover.1425889432.git.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>
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
next prev parent reply other threads:[~2015-03-09 8:36 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-09 8:34 [PATCH 00/10] rcu: Cleanup RCU tree initialization Alexander Gordeev
2015-03-09 8:34 ` [PATCH 01/10] rcu: Panic if RCU tree can not accommodate all CPUs Alexander Gordeev
2015-03-09 8:34 ` [PATCH 02/10] rcu: Remove superfluous local variable in rcu_init_geometry() Alexander Gordeev
2015-03-09 8:34 ` [PATCH 03/10] rcu: Cleanup rcu_init_geometry() code and arithmetics Alexander Gordeev
2015-03-09 8:34 ` [PATCH 04/10] rcu: Simplify rcu_init_geometry() capacity arithmetics Alexander Gordeev
2015-03-09 8:34 ` Alexander Gordeev [this message]
2015-03-09 8:34 ` [PATCH 06/10] rcu: Limit rcu_capacity[] size to RCU_NUM_LVLS items Alexander Gordeev
2015-03-09 8:34 ` [PATCH 07/10] rcu: Remove unnecessary fields from rcu_state structure Alexander Gordeev
2015-03-09 8:34 ` [PATCH 08/10] rcu: Limit count of static data to the number of RCU levels Alexander Gordeev
2015-03-09 8:34 ` [PATCH 09/10] rcu: Simplify arithmetic to calculate number of RCU nodes Alexander Gordeev
2015-03-09 8:34 ` [PATCH 10/10] rcu: Remove unnecessary grpnum field from rcu_node structure Alexander Gordeev
2015-03-09 9:36 ` [PATCH 00/10] rcu: Cleanup RCU tree initialization Alexander Gordeev
2015-03-09 21:35 ` Paul E. McKenney
2015-03-10 14:33 ` Alexander Gordeev
2015-03-10 14:57 ` Paul E. McKenney
2015-03-09 21:40 ` Paul E. McKenney
2015-03-09 23:39 ` Paul E. McKenney
2015-03-09 23:49 ` Paul E. McKenney
2015-03-10 4:43 ` Paul E. McKenney
2015-03-10 14:39 ` Alexander Gordeev
2015-03-10 14:52 ` Paul E. McKenney
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