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 <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Paul E. McKenney
Paul E. McKenney
parent
0ac3d136b2
commit
d71df90ead
4 changed files with 44 additions and 4 deletions
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@ -91,8 +91,9 @@ EXPORT_SYMBOL_GPL(rcu_scheduler_active);
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* handle all flavors of RCU.
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*/
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static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task);
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DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
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static DEFINE_PER_CPU(wait_queue_head_t, rcu_cpu_wq);
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static DEFINE_PER_CPU(char, rcu_cpu_has_work);
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DEFINE_PER_CPU(char, rcu_cpu_has_work);
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static char rcu_kthreads_spawnable;
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static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
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@ -1563,11 +1564,13 @@ static int rcu_cpu_kthread(void *arg)
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int cpu = (int)(long)arg;
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unsigned long flags;
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int spincnt = 0;
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unsigned int *statusp = &per_cpu(rcu_cpu_kthread_status, cpu);
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wait_queue_head_t *wqp = &per_cpu(rcu_cpu_wq, cpu);
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char work;
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char *workp = &per_cpu(rcu_cpu_has_work, cpu);
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for (;;) {
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*statusp = RCU_KTHREAD_WAITING;
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wait_event_interruptible(*wqp,
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*workp != 0 || kthread_should_stop());
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local_bh_disable();
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@ -1575,6 +1578,7 @@ static int rcu_cpu_kthread(void *arg)
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local_bh_enable();
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break;
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}
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*statusp = RCU_KTHREAD_RUNNING;
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local_irq_save(flags);
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work = *workp;
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*workp = 0;
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@ -1587,10 +1591,12 @@ static int rcu_cpu_kthread(void *arg)
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else
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spincnt = 0;
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if (spincnt > 10) {
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*statusp = RCU_KTHREAD_YIELDING;
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rcu_yield(rcu_cpu_kthread_timer, (unsigned long)cpu);
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spincnt = 0;
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}
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}
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*statusp = RCU_KTHREAD_STOPPED;
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return 0;
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}
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@ -1637,10 +1643,12 @@ static int rcu_node_kthread(void *arg)
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struct task_struct *t;
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for (;;) {
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rnp->node_kthread_status = RCU_KTHREAD_WAITING;
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wait_event_interruptible(rnp->node_wq, rnp->wakemask != 0 ||
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kthread_should_stop());
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if (kthread_should_stop())
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break;
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rnp->node_kthread_status = RCU_KTHREAD_RUNNING;
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raw_spin_lock_irqsave(&rnp->lock, flags);
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mask = rnp->wakemask;
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rnp->wakemask = 0;
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@ -1661,6 +1669,7 @@ static int rcu_node_kthread(void *arg)
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preempt_enable();
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}
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}
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rnp->node_kthread_status = RCU_KTHREAD_STOPPED;
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return 0;
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}
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@ -89,6 +89,13 @@ struct rcu_dynticks {
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atomic_t dynticks; /* Even value for dynticks-idle, else odd. */
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};
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/* RCU's kthread states for tracing. */
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#define RCU_KTHREAD_STOPPED 0
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#define RCU_KTHREAD_RUNNING 1
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#define RCU_KTHREAD_WAITING 2
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#define RCU_KTHREAD_YIELDING 3
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#define RCU_KTHREAD_MAX 3
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/*
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* Definition for node within the RCU grace-period-detection hierarchy.
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*/
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@ -152,6 +159,8 @@ struct rcu_node {
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wait_queue_head_t boost_wq;
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/* Wait queue on which to park the boost */
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/* kthread. */
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unsigned int boost_kthread_status;
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/* State of boost_kthread_task for tracing. */
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unsigned long n_tasks_boosted;
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/* Total number of tasks boosted. */
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unsigned long n_exp_boosts;
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@ -179,6 +188,8 @@ struct rcu_node {
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wait_queue_head_t node_wq;
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/* Wait queue on which to park the per-node */
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/* kthread. */
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unsigned int node_kthread_status;
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/* State of node_kthread_task for tracing. */
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} ____cacheline_internodealigned_in_smp;
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/*
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@ -1198,11 +1198,13 @@ static int rcu_boost_kthread(void *arg)
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int more2boost;
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for (;;) {
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rnp->boost_kthread_status = RCU_KTHREAD_WAITING;
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wait_event_interruptible(rnp->boost_wq, rnp->boost_tasks ||
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rnp->exp_tasks ||
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kthread_should_stop());
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if (kthread_should_stop())
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break;
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rnp->boost_kthread_status = RCU_KTHREAD_RUNNING;
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more2boost = rcu_boost(rnp);
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if (more2boost)
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spincnt++;
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@ -1213,6 +1215,7 @@ static int rcu_boost_kthread(void *arg)
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spincnt = 0;
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}
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}
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rnp->boost_kthread_status = RCU_KTHREAD_STOPPED;
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return 0;
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}
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@ -46,6 +46,16 @@
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#define RCU_TREE_NONCORE
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#include "rcutree.h"
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DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
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DECLARE_PER_CPU(char, rcu_cpu_has_work);
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static char convert_kthread_status(unsigned int kthread_status)
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{
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if (kthread_status > RCU_KTHREAD_MAX)
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return '?';
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return "SRWY"[kthread_status];
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}
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static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
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{
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if (!rdp->beenonline)
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@ -64,7 +74,7 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
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rdp->dynticks_fqs);
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#endif /* #ifdef CONFIG_NO_HZ */
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seq_printf(m, " of=%lu ri=%lu", rdp->offline_fqs, rdp->resched_ipi);
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seq_printf(m, " ql=%ld qs=%c%c%c%c b=%ld",
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seq_printf(m, " ql=%ld qs=%c%c%c%c kt=%d/%c b=%ld",
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rdp->qlen,
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".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] !=
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rdp->nxttail[RCU_NEXT_TAIL]],
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@ -73,6 +83,9 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
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".W"[rdp->nxttail[RCU_DONE_TAIL] !=
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rdp->nxttail[RCU_WAIT_TAIL]],
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".D"[&rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]],
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per_cpu(rcu_cpu_has_work, rdp->cpu),
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convert_kthread_status(per_cpu(rcu_cpu_kthread_status,
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rdp->cpu)),
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rdp->blimit);
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seq_printf(m, " ci=%lu co=%lu ca=%lu\n",
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rdp->n_cbs_invoked, rdp->n_cbs_orphaned, rdp->n_cbs_adopted);
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@ -130,7 +143,7 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp)
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rdp->dynticks_fqs);
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#endif /* #ifdef CONFIG_NO_HZ */
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seq_printf(m, ",%lu,%lu", rdp->offline_fqs, rdp->resched_ipi);
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seq_printf(m, ",%ld,\"%c%c%c%c\",%ld", rdp->qlen,
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seq_printf(m, ",%ld,\"%c%c%c%c\",%d,\"%c\",%ld", rdp->qlen,
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".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] !=
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rdp->nxttail[RCU_NEXT_TAIL]],
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".R"[rdp->nxttail[RCU_WAIT_TAIL] !=
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@ -138,6 +151,9 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp)
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".W"[rdp->nxttail[RCU_DONE_TAIL] !=
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rdp->nxttail[RCU_WAIT_TAIL]],
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".D"[&rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]],
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per_cpu(rcu_cpu_has_work, rdp->cpu),
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convert_kthread_status(per_cpu(rcu_cpu_kthread_status,
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rdp->cpu)),
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rdp->blimit);
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seq_printf(m, ",%lu,%lu,%lu\n",
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rdp->n_cbs_invoked, rdp->n_cbs_orphaned, rdp->n_cbs_adopted);
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@ -178,13 +194,14 @@ static const struct file_operations rcudata_csv_fops = {
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static void print_one_rcu_node_boost(struct seq_file *m, struct rcu_node *rnp)
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{
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seq_printf(m, "%d:%d tasks=%c%c%c%c ntb=%lu neb=%lu nnb=%lu "
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seq_printf(m, "%d:%d tasks=%c%c%c%c kt=%c ntb=%lu neb=%lu nnb=%lu "
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"j=%04x bt=%04x\n",
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rnp->grplo, rnp->grphi,
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"T."[list_empty(&rnp->blkd_tasks)],
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"N."[!rnp->gp_tasks],
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"E."[!rnp->exp_tasks],
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"B."[!rnp->boost_tasks],
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convert_kthread_status(rnp->boost_kthread_status),
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rnp->n_tasks_boosted, rnp->n_exp_boosts,
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rnp->n_normal_boosts,
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(int)(jiffies & 0xffff),
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