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SubjectRe: [PATCH RFC tip/core/rcu 15/18] rcu: give different levels of the rcu_node hierarchy distinct lockdep names
On Tue, Dec 15, 2009 at 03:02:38PM -0800, Paul E. McKenney wrote:
> From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>
> Proposed for 2.6.34, not for inclusion.
>
> 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.
>
> 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..a6e45f6 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;
>
> + WARN_ON_ONCE(MAX_RCU_LVLS > 4); /* Fix buf[] initialization! */
> +

BUILD_BUG_ON seems better. For that matter, please consider moving
these near the rest of the level-specific defines, making them const,
and ideally not emitting the strings for levels you don't have.

- Josh Triplett


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