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Message-ID: <1260959160.17860.39.camel@laptop>
Date: Wed, 16 Dec 2009 11:26:00 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc: linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
dipankar@...ibm.com, akpm@...ux-foundation.org,
mathieu.desnoyers@...ymtl.ca, josh@...htriplett.org,
dvhltc@...ibm.com, niv@...ibm.com, tglx@...utronix.de,
rostedt@...dmis.org, Valdis.Kletnieks@...edu, dhowells@...hat.com
Subject: Re: [PATCH RFC tip/core/rcu 15/18] rcu: give different levels of
the rcu_node hierarchy distinct lockdep names
On Tue, 2009-12-15 at 15:02 -0800, Paul E. McKenney wrote:
> From: Paul E. McKenney <paulmck@...ux.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@...ux.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! */
So you're going to WARN here,
> /* 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]);
and segfault here because i overruns its bounds?
Might as well BUG_ON then.
--
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