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Commit d71df90e authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Paul E. McKenney
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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: default avatarPaul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent 0ac3d136
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Inline Side-by-side
Showing with 44 additions and 4 deletions
kernel/rcutree.c
View file @ d71df90e
...@@ -91,8 +91,9 @@ EXPORT_SYMBOL_GPL(rcu_scheduler_active); ...@@ -91,8 +91,9 @@ EXPORT_SYMBOL_GPL(rcu_scheduler_active);
* handle all flavors of RCU. * handle all flavors of RCU.
*/ */
static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); 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(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 char rcu_kthreads_spawnable;
static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
...@@ -1563,11 +1564,13 @@ static int rcu_cpu_kthread(void *arg) ...@@ -1563,11 +1564,13 @@ static int rcu_cpu_kthread(void *arg)
int cpu = (int)(long)arg; int cpu = (int)(long)arg;
unsigned long flags; unsigned long flags;
int spincnt = 0; int spincnt = 0;
unsigned int *statusp = &per_cpu(rcu_cpu_kthread_status, cpu);
wait_queue_head_t *wqp = &per_cpu(rcu_cpu_wq, cpu); wait_queue_head_t *wqp = &per_cpu(rcu_cpu_wq, cpu);
char work; char work;
char *workp = &per_cpu(rcu_cpu_has_work, cpu); char *workp = &per_cpu(rcu_cpu_has_work, cpu);
for (;;) { for (;;) {
*statusp = RCU_KTHREAD_WAITING;
wait_event_interruptible(*wqp, wait_event_interruptible(*wqp,
*workp != 0 || kthread_should_stop()); *workp != 0 || kthread_should_stop());
local_bh_disable(); local_bh_disable();
...@@ -1575,6 +1578,7 @@ static int rcu_cpu_kthread(void *arg) ...@@ -1575,6 +1578,7 @@ static int rcu_cpu_kthread(void *arg)
local_bh_enable(); local_bh_enable();
break; break;
} }
*statusp = RCU_KTHREAD_RUNNING;
local_irq_save(flags); local_irq_save(flags);
work = *workp; work = *workp;
*workp = 0; *workp = 0;
...@@ -1587,10 +1591,12 @@ static int rcu_cpu_kthread(void *arg) ...@@ -1587,10 +1591,12 @@ static int rcu_cpu_kthread(void *arg)
else else
spincnt = 0; spincnt = 0;
if (spincnt > 10) { if (spincnt > 10) {
*statusp = RCU_KTHREAD_YIELDING;
rcu_yield(rcu_cpu_kthread_timer, (unsigned long)cpu); rcu_yield(rcu_cpu_kthread_timer, (unsigned long)cpu);
spincnt = 0; spincnt = 0;
} }
} }
*statusp = RCU_KTHREAD_STOPPED;
return 0; return 0;
} }
...@@ -1637,10 +1643,12 @@ static int rcu_node_kthread(void *arg) ...@@ -1637,10 +1643,12 @@ static int rcu_node_kthread(void *arg)
struct task_struct *t; struct task_struct *t;
for (;;) { for (;;) {
rnp->node_kthread_status = RCU_KTHREAD_WAITING;
wait_event_interruptible(rnp->node_wq, rnp->wakemask != 0 || wait_event_interruptible(rnp->node_wq, rnp->wakemask != 0 ||
kthread_should_stop()); kthread_should_stop());
if (kthread_should_stop()) if (kthread_should_stop())
break; break;
rnp->node_kthread_status = RCU_KTHREAD_RUNNING;
raw_spin_lock_irqsave(&rnp->lock, flags); raw_spin_lock_irqsave(&rnp->lock, flags);
mask = rnp->wakemask; mask = rnp->wakemask;
rnp->wakemask = 0; rnp->wakemask = 0;
...@@ -1661,6 +1669,7 @@ static int rcu_node_kthread(void *arg) ...@@ -1661,6 +1669,7 @@ static int rcu_node_kthread(void *arg)
preempt_enable(); preempt_enable();
} }
} }
rnp->node_kthread_status = RCU_KTHREAD_STOPPED;
return 0; return 0;
} }
......
kernel/rcutree.h
View file @ d71df90e
...@@ -89,6 +89,13 @@ struct rcu_dynticks { ...@@ -89,6 +89,13 @@ struct rcu_dynticks {
atomic_t dynticks; /* Even value for dynticks-idle, else odd. */ 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. * Definition for node within the RCU grace-period-detection hierarchy.
*/ */
...@@ -152,6 +159,8 @@ struct rcu_node { ...@@ -152,6 +159,8 @@ struct rcu_node {
wait_queue_head_t boost_wq; wait_queue_head_t boost_wq;
/* Wait queue on which to park the boost */ /* Wait queue on which to park the boost */
/* kthread. */ /* kthread. */
unsigned int boost_kthread_status;
/* State of boost_kthread_task for tracing. */
unsigned long n_tasks_boosted; unsigned long n_tasks_boosted;
/* Total number of tasks boosted. */ /* Total number of tasks boosted. */
unsigned long n_exp_boosts; unsigned long n_exp_boosts;
...@@ -179,6 +188,8 @@ struct rcu_node { ...@@ -179,6 +188,8 @@ struct rcu_node {
wait_queue_head_t node_wq; wait_queue_head_t node_wq;
/* Wait queue on which to park the per-node */ /* Wait queue on which to park the per-node */
/* kthread. */ /* kthread. */
unsigned int node_kthread_status;
/* State of node_kthread_task for tracing. */
} ____cacheline_internodealigned_in_smp; } ____cacheline_internodealigned_in_smp;
/* /*
......
kernel/rcutree_plugin.h
View file @ d71df90e
...@@ -1198,11 +1198,13 @@ static int rcu_boost_kthread(void *arg) ...@@ -1198,11 +1198,13 @@ static int rcu_boost_kthread(void *arg)
int more2boost; int more2boost;
for (;;) { for (;;) {
rnp->boost_kthread_status = RCU_KTHREAD_WAITING;
wait_event_interruptible(rnp->boost_wq, rnp->boost_tasks || wait_event_interruptible(rnp->boost_wq, rnp->boost_tasks ||
rnp->exp_tasks || rnp->exp_tasks ||
kthread_should_stop()); kthread_should_stop());
if (kthread_should_stop()) if (kthread_should_stop())
break; break;
rnp->boost_kthread_status = RCU_KTHREAD_RUNNING;
more2boost = rcu_boost(rnp); more2boost = rcu_boost(rnp);
if (more2boost) if (more2boost)
spincnt++; spincnt++;
...@@ -1213,6 +1215,7 @@ static int rcu_boost_kthread(void *arg) ...@@ -1213,6 +1215,7 @@ static int rcu_boost_kthread(void *arg)
spincnt = 0; spincnt = 0;
} }
} }
rnp->boost_kthread_status = RCU_KTHREAD_STOPPED;
return 0; return 0;
} }
......
kernel/rcutree_trace.c
View file @ d71df90e
...@@ -46,6 +46,16 @@ ...@@ -46,6 +46,16 @@
#define RCU_TREE_NONCORE #define RCU_TREE_NONCORE
#include "rcutree.h" #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) static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
{ {
if (!rdp->beenonline) if (!rdp->beenonline)
...@@ -64,7 +74,7 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) ...@@ -64,7 +74,7 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
rdp->dynticks_fqs); rdp->dynticks_fqs);
#endif /* #ifdef CONFIG_NO_HZ */ #endif /* #ifdef CONFIG_NO_HZ */
seq_printf(m, " of=%lu ri=%lu", rdp->offline_fqs, rdp->resched_ipi); 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, rdp->qlen,
".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] != ".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] !=
rdp->nxttail[RCU_NEXT_TAIL]], rdp->nxttail[RCU_NEXT_TAIL]],
...@@ -73,6 +83,9 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) ...@@ -73,6 +83,9 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
".W"[rdp->nxttail[RCU_DONE_TAIL] != ".W"[rdp->nxttail[RCU_DONE_TAIL] !=
rdp->nxttail[RCU_WAIT_TAIL]], rdp->nxttail[RCU_WAIT_TAIL]],
".D"[&rdp->nxtlist != rdp->nxttail[RCU_DONE_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); rdp->blimit);
seq_printf(m, " ci=%lu co=%lu ca=%lu\n", seq_printf(m, " ci=%lu co=%lu ca=%lu\n",
rdp->n_cbs_invoked, rdp->n_cbs_orphaned, rdp->n_cbs_adopted); 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) ...@@ -130,7 +143,7 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp)
rdp->dynticks_fqs); rdp->dynticks_fqs);
#endif /* #ifdef CONFIG_NO_HZ */ #endif /* #ifdef CONFIG_NO_HZ */
seq_printf(m, ",%lu,%lu", rdp->offline_fqs, rdp->resched_ipi); 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] != ".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] !=
rdp->nxttail[RCU_NEXT_TAIL]], rdp->nxttail[RCU_NEXT_TAIL]],
".R"[rdp->nxttail[RCU_WAIT_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) ...@@ -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] != ".W"[rdp->nxttail[RCU_DONE_TAIL] !=
rdp->nxttail[RCU_WAIT_TAIL]], rdp->nxttail[RCU_WAIT_TAIL]],
".D"[&rdp->nxtlist != rdp->nxttail[RCU_DONE_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); rdp->blimit);
seq_printf(m, ",%lu,%lu,%lu\n", seq_printf(m, ",%lu,%lu,%lu\n",
rdp->n_cbs_invoked, rdp->n_cbs_orphaned, rdp->n_cbs_adopted); rdp->n_cbs_invoked, rdp->n_cbs_orphaned, rdp->n_cbs_adopted);
...@@ -178,13 +194,14 @@ static const struct file_operations rcudata_csv_fops = { ...@@ -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) 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", "j=%04x bt=%04x\n",
rnp->grplo, rnp->grphi, rnp->grplo, rnp->grphi,
"T."[list_empty(&rnp->blkd_tasks)], "T."[list_empty(&rnp->blkd_tasks)],
"N."[!rnp->gp_tasks], "N."[!rnp->gp_tasks],
"E."[!rnp->exp_tasks], "E."[!rnp->exp_tasks],
"B."[!rnp->boost_tasks], "B."[!rnp->boost_tasks],
convert_kthread_status(rnp->boost_kthread_status),
rnp->n_tasks_boosted, rnp->n_exp_boosts, rnp->n_tasks_boosted, rnp->n_exp_boosts,
rnp->n_normal_boosts, rnp->n_normal_boosts,
(int)(jiffies & 0xffff), (int)(jiffies & 0xffff),
......
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