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Subject[PATCH tip/core/rcu 3/3] rcu: give different levels of the rcu_node hierarchy distinct lockdep names
Date
From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Previously, each level of the rcu_node hierarchy had the same rather
unimaginative name: "&rcu_node_class[i]". This makes lockdep diagnostics
involving these lockdep classes less helpful than would be nice.
This patch fixes this by giving each level of the rcu_node hierarchy
a distinct name: "rcu_node_level_0", "rcu_node_level_1", and so on.
This version of the patch includes improved diagnostics suggested by
Josh Triplett and Peter Zijlstra.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcutree.c | 9 ++++++++-
1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 0a4c328..3b13d64 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1811,11 +1811,17 @@ static void __init rcu_init_levelspread(struct rcu_state *rsp)
*/
static void __init rcu_init_one(struct rcu_state *rsp)
{
+ static char *buf[] = { "rcu_node_level_0",
+ "rcu_node_level_1",
+ "rcu_node_level_2",
+ "rcu_node_level_3" }; /* Match MAX_RCU_LVLS */
int cpustride = 1;
int i;
int j;
struct rcu_node *rnp;

+ BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
+
/* Initialize the level-tracking arrays. */

for (i = 1; i < NUM_RCU_LVLS; i++)
@@ -1829,7 +1835,8 @@ static void __init rcu_init_one(struct rcu_state *rsp)
rnp = rsp->level[i];
for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) {
spin_lock_init(&rnp->lock);
- lockdep_set_class(&rnp->lock, &rcu_node_class[i]);
+ lockdep_set_class_and_name(&rnp->lock,
+ &rcu_node_class[i], buf[i]);
rnp->gpnum = 0;
rnp->qsmask = 0;
rnp->qsmaskinit = 0;
--
1.5.2.5


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