From d71df90eadfc35aa549ff9a850842673febca71f Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 29 Mar 2011 17:48:28 -0700 Subject: rcu: add tracing for RCU's kthread run states. Add tracing to help debugging situations when RCU's kthreads are not running but are supposed to be. Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- kernel/rcutree.c | 11 ++++++++++- kernel/rcutree.h | 11 +++++++++++ kernel/rcutree_plugin.h | 3 +++ kernel/rcutree_trace.c | 23 ++++++++++++++++++++--- 4 files changed, 44 insertions(+), 4 deletions(-) diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 198e4df7d83..d8917401cbb 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -91,8 +91,9 @@ EXPORT_SYMBOL_GPL(rcu_scheduler_active); * handle all flavors of RCU. */ static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); +DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); static DEFINE_PER_CPU(wait_queue_head_t, rcu_cpu_wq); -static DEFINE_PER_CPU(char, rcu_cpu_has_work); +DEFINE_PER_CPU(char, rcu_cpu_has_work); static char rcu_kthreads_spawnable; static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); @@ -1563,11 +1564,13 @@ static int rcu_cpu_kthread(void *arg) int cpu = (int)(long)arg; unsigned long flags; int spincnt = 0; + unsigned int *statusp = &per_cpu(rcu_cpu_kthread_status, cpu); wait_queue_head_t *wqp = &per_cpu(rcu_cpu_wq, cpu); char work; char *workp = &per_cpu(rcu_cpu_has_work, cpu); for (;;) { + *statusp = RCU_KTHREAD_WAITING; wait_event_interruptible(*wqp, *workp != 0 || kthread_should_stop()); local_bh_disable(); @@ -1575,6 +1578,7 @@ static int rcu_cpu_kthread(void *arg) local_bh_enable(); break; } + *statusp = RCU_KTHREAD_RUNNING; local_irq_save(flags); work = *workp; *workp = 0; @@ -1587,10 +1591,12 @@ static int rcu_cpu_kthread(void *arg) else spincnt = 0; if (spincnt > 10) { + *statusp = RCU_KTHREAD_YIELDING; rcu_yield(rcu_cpu_kthread_timer, (unsigned long)cpu); spincnt = 0; } } + *statusp = RCU_KTHREAD_STOPPED; return 0; } @@ -1637,10 +1643,12 @@ static int rcu_node_kthread(void *arg) struct task_struct *t; for (;;) { + rnp->node_kthread_status = RCU_KTHREAD_WAITING; wait_event_interruptible(rnp->node_wq, rnp->wakemask != 0 || kthread_should_stop()); if (kthread_should_stop()) break; + rnp->node_kthread_status = RCU_KTHREAD_RUNNING; raw_spin_lock_irqsave(&rnp->lock, flags); mask = rnp->wakemask; rnp->wakemask = 0; @@ -1661,6 +1669,7 @@ static int rcu_node_kthread(void *arg) preempt_enable(); } } + rnp->node_kthread_status = RCU_KTHREAD_STOPPED; return 0; } diff --git a/kernel/rcutree.h b/kernel/rcutree.h index d49046c79c5..67341dbebd9 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -89,6 +89,13 @@ struct rcu_dynticks { atomic_t dynticks; /* Even value for dynticks-idle, else odd. */ }; +/* RCU's kthread states for tracing. */ +#define RCU_KTHREAD_STOPPED 0 +#define RCU_KTHREAD_RUNNING 1 +#define RCU_KTHREAD_WAITING 2 +#define RCU_KTHREAD_YIELDING 3 +#define RCU_KTHREAD_MAX 3 + /* * Definition for node within the RCU grace-period-detection hierarchy. */ @@ -152,6 +159,8 @@ struct rcu_node { wait_queue_head_t boost_wq; /* Wait queue on which to park the boost */ /* kthread. */ + unsigned int boost_kthread_status; + /* State of boost_kthread_task for tracing. */ unsigned long n_tasks_boosted; /* Total number of tasks boosted. */ unsigned long n_exp_boosts; @@ -179,6 +188,8 @@ struct rcu_node { wait_queue_head_t node_wq; /* Wait queue on which to park the per-node */ /* kthread. */ + unsigned int node_kthread_status; + /* State of node_kthread_task for tracing. */ } ____cacheline_internodealigned_in_smp; /* diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 07d346445d1..22a6a46de7c 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -1198,11 +1198,13 @@ static int rcu_boost_kthread(void *arg) int more2boost; for (;;) { + rnp->boost_kthread_status = RCU_KTHREAD_WAITING; wait_event_interruptible(rnp->boost_wq, rnp->boost_tasks || rnp->exp_tasks || kthread_should_stop()); if (kthread_should_stop()) break; + rnp->boost_kthread_status = RCU_KTHREAD_RUNNING; more2boost = rcu_boost(rnp); if (more2boost) spincnt++; @@ -1213,6 +1215,7 @@ static int rcu_boost_kthread(void *arg) spincnt = 0; } } + rnp->boost_kthread_status = RCU_KTHREAD_STOPPED; return 0; } diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c index afd262f9126..fc40e89a028 100644 --- a/kernel/rcutree_trace.c +++ b/kernel/rcutree_trace.c @@ -46,6 +46,16 @@ #define RCU_TREE_NONCORE #include "rcutree.h" +DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status); +DECLARE_PER_CPU(char, rcu_cpu_has_work); + +static char convert_kthread_status(unsigned int kthread_status) +{ + if (kthread_status > RCU_KTHREAD_MAX) + return '?'; + return "SRWY"[kthread_status]; +} + static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) { if (!rdp->beenonline) @@ -64,7 +74,7 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) rdp->dynticks_fqs); #endif /* #ifdef CONFIG_NO_HZ */ seq_printf(m, " of=%lu ri=%lu", rdp->offline_fqs, rdp->resched_ipi); - seq_printf(m, " ql=%ld qs=%c%c%c%c b=%ld", + seq_printf(m, " ql=%ld qs=%c%c%c%c kt=%d/%c b=%ld", rdp->qlen, ".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] != rdp->nxttail[RCU_NEXT_TAIL]], @@ -73,6 +83,9 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) ".W"[rdp->nxttail[RCU_DONE_TAIL] != rdp->nxttail[RCU_WAIT_TAIL]], ".D"[&rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]], + per_cpu(rcu_cpu_has_work, rdp->cpu), + convert_kthread_status(per_cpu(rcu_cpu_kthread_status, + rdp->cpu)), rdp->blimit); seq_printf(m, " ci=%lu co=%lu ca=%lu\n", rdp->n_cbs_invoked, rdp->n_cbs_orphaned, rdp->n_cbs_adopted); @@ -130,7 +143,7 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp) rdp->dynticks_fqs); #endif /* #ifdef CONFIG_NO_HZ */ seq_printf(m, ",%lu,%lu", rdp->offline_fqs, rdp->resched_ipi); - seq_printf(m, ",%ld,\"%c%c%c%c\",%ld", rdp->qlen, + seq_printf(m, ",%ld,\"%c%c%c%c\",%d,\"%c\",%ld", rdp->qlen, ".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] != rdp->nxttail[RCU_NEXT_TAIL]], ".R"[rdp->nxttail[RCU_WAIT_TAIL] != @@ -138,6 +151,9 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp) ".W"[rdp->nxttail[RCU_DONE_TAIL] != rdp->nxttail[RCU_WAIT_TAIL]], ".D"[&rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]], + per_cpu(rcu_cpu_has_work, rdp->cpu), + convert_kthread_status(per_cpu(rcu_cpu_kthread_status, + rdp->cpu)), rdp->blimit); seq_printf(m, ",%lu,%lu,%lu\n", rdp->n_cbs_invoked, rdp->n_cbs_orphaned, rdp->n_cbs_adopted); @@ -178,13 +194,14 @@ static const struct file_operations rcudata_csv_fops = { static void print_one_rcu_node_boost(struct seq_file *m, struct rcu_node *rnp) { - seq_printf(m, "%d:%d tasks=%c%c%c%c ntb=%lu neb=%lu nnb=%lu " + seq_printf(m, "%d:%d tasks=%c%c%c%c kt=%c ntb=%lu neb=%lu nnb=%lu " "j=%04x bt=%04x\n", rnp->grplo, rnp->grphi, "T."[list_empty(&rnp->blkd_tasks)], "N."[!rnp->gp_tasks], "E."[!rnp->exp_tasks], "B."[!rnp->boost_tasks], + convert_kthread_status(rnp->boost_kthread_status), rnp->n_tasks_boosted, rnp->n_exp_boosts, rnp->n_normal_boosts, (int)(jiffies & 0xffff), -- cgit v1.2.3