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    Subject[tip:core/rcu] rcu: Give different levels of the rcu_node hierarchy distinct lockdep names
    Commit-ID:  b6407e863934965cdc66cbc244d811ceeb6f4d77
    Gitweb: http://git.kernel.org/tip/b6407e863934965cdc66cbc244d811ceeb6f4d77
    Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    AuthorDate: Mon, 4 Jan 2010 16:04:02 -0800
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Wed, 13 Jan 2010 09:06:07 +0100

    rcu: Give different levels of the rcu_node hierarchy distinct lockdep names

    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>
    Cc: laijs@cn.fujitsu.com
    Cc: dipankar@in.ibm.com
    Cc: mathieu.desnoyers@polymtl.ca
    Cc: josh@joshtriplett.org
    Cc: dvhltc@us.ibm.com
    Cc: niv@us.ibm.com
    Cc: peterz@infradead.org
    Cc: rostedt@goodmis.org
    Cc: Valdis.Kletnieks@vt.edu
    Cc: dhowells@redhat.com
    LKML-Reference: <12626498421830-git-send-email->
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    ---
    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;

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