From a3dc2948cec80f20a89e9b646d0c01b121e48e02 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 20 Apr 2015 11:40:50 -0700 Subject: [PATCH] rcu: Enable diagnostic dump of rcu_node combining tree The purpose of this commit is to make it easier to verify that RCU's combining tree is set up correctly, which is useful to have when making changes in how that tree is initialized. Signed-off-by: Paul E. McKenney Reviewed-by: Pranith Kumar [ paulmck: Fold fix found by Fengguang's 0-day test robot. ] --- Documentation/kernel-parameters.txt | 5 +++++ kernel/rcu/tree.c | 27 +++++++++++++++++++++++++++ 2 files changed, 32 insertions(+) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index f5582dc..a1cb88d 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -2992,6 +2992,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. Set maximum number of finished RCU callbacks to process in one batch. + rcutree.dump_tree= [KNL] + Dump the structure of the rcu_node combining tree + out at early boot. This is used for diagnostic + purposes, to verify correct tree setup. + rcutree.gp_cleanup_delay= [KNL] Set the number of jiffies to delay each step of RCU grace-period cleanup. This only has effect diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index b49c474..1bc14c6 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -113,6 +113,9 @@ RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh); static struct rcu_state *rcu_state_p; LIST_HEAD(rcu_struct_flavors); +/* Dump rcu_node combining tree at boot to verify correct setup. */ +static bool dump_tree; +module_param(dump_tree, bool, 0444); /* Control rcu_node-tree auto-balancing at boot time. */ static bool rcu_fanout_exact; module_param(rcu_fanout_exact, bool, 0444); @@ -4144,6 +4147,28 @@ static void __init rcu_init_geometry(void) rcu_num_nodes -= n; } +/* + * Dump out the structure of the rcu_node combining tree associated + * with the rcu_state structure referenced by rsp. + */ +static void __init rcu_dump_rcu_node_tree(struct rcu_state *rsp) +{ + int level = 0; + struct rcu_node *rnp; + + pr_info("rcu_node tree layout dump\n"); + pr_info(" "); + rcu_for_each_node_breadth_first(rsp, rnp) { + if (rnp->level != level) { + pr_cont("\n"); + pr_info(" "); + level = rnp->level; + } + pr_cont("%d:%d ^%d ", rnp->grplo, rnp->grphi, rnp->grpnum); + } + pr_cont("\n"); +} + void __init rcu_init(void) { int cpu; @@ -4154,6 +4179,8 @@ void __init rcu_init(void) rcu_init_geometry(); rcu_init_one(&rcu_bh_state, &rcu_bh_data); rcu_init_one(&rcu_sched_state, &rcu_sched_data); + if (dump_tree) + rcu_dump_rcu_node_tree(&rcu_sched_state); __rcu_init_preempt(); open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); -- 2.7.4