[PATCH tip/core/rcu 09/20] rcu: Remove obsolete __rcu_pending() statistics for debugfs

From: Paul E. McKenney
Date: Mon Feb 26 2018 - 16:57:50 EST


The debugfs interface displayed statistics on RCU-pending checks
but this interface has since been removed. This commit therefore
removes the no-longer-used rcu_data structure's ->n_rcu_pending,
->n_rp_core_needs_qs, ->n_rp_report_qs, ->n_rp_cb_ready,
->n_rp_cpu_needs_gp, ->n_rp_gp_completed, ->n_rp_gp_started,
->n_rp_nocb_defer_wakeup, and ->n_rp_need_nothing fields along with
their updates.

If this information proves necessary in the future, the corresponding
event traces will be added.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tree.c | 31 ++++++-------------------------
kernel/rcu/tree.h | 17 +++--------------
2 files changed, 9 insertions(+), 39 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 8e0711954bbf..99d59be761d1 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3354,8 +3354,6 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
{
struct rcu_node *rnp = rdp->mynode;

- rdp->n_rcu_pending++;
-
/* Check for CPU stalls, if enabled. */
check_cpu_stall(rsp, rdp);

@@ -3364,48 +3362,31 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
return 0;

/* Is the RCU core waiting for a quiescent state from this CPU? */
- if (rcu_scheduler_fully_active &&
- rdp->core_needs_qs && rdp->cpu_no_qs.b.norm &&
- rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_dynticks.rcu_qs_ctr)) {
- rdp->n_rp_core_needs_qs++;
- } else if (rdp->core_needs_qs && !rdp->cpu_no_qs.b.norm) {
- rdp->n_rp_report_qs++;
+ if (rdp->core_needs_qs && !rdp->cpu_no_qs.b.norm)
return 1;
- }

/* Does this CPU have callbacks ready to invoke? */
- if (rcu_segcblist_ready_cbs(&rdp->cblist)) {
- rdp->n_rp_cb_ready++;
+ if (rcu_segcblist_ready_cbs(&rdp->cblist))
return 1;
- }

/* Has RCU gone idle with this CPU needing another grace period? */
- if (cpu_needs_another_gp(rsp, rdp)) {
- rdp->n_rp_cpu_needs_gp++;
+ if (cpu_needs_another_gp(rsp, rdp))
return 1;
- }

/* Has another RCU grace period completed? */
- if (READ_ONCE(rnp->completed) != rdp->completed) { /* outside lock */
- rdp->n_rp_gp_completed++;
+ if (READ_ONCE(rnp->completed) != rdp->completed) /* outside lock */
return 1;
- }

/* Has a new RCU grace period started? */
if (READ_ONCE(rnp->gpnum) != rdp->gpnum ||
- unlikely(READ_ONCE(rdp->gpwrap))) { /* outside lock */
- rdp->n_rp_gp_started++;
+ unlikely(READ_ONCE(rdp->gpwrap))) /* outside lock */
return 1;
- }

/* Does this CPU need a deferred NOCB wakeup? */
- if (rcu_nocb_need_deferred_wakeup(rdp)) {
- rdp->n_rp_nocb_defer_wakeup++;
+ if (rcu_nocb_need_deferred_wakeup(rdp))
return 1;
- }

/* nothing to do */
- rdp->n_rp_need_nothing++;
return 0;
}

diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index b258fac73524..d29bab8dea28 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -226,18 +226,7 @@ struct rcu_data {
/* Grace period that needs help */
/* from cond_resched(). */

- /* 5) __rcu_pending() statistics. */
- unsigned long n_rcu_pending; /* rcu_pending() calls since boot. */
- unsigned long n_rp_core_needs_qs;
- unsigned long n_rp_report_qs;
- unsigned long n_rp_cb_ready;
- unsigned long n_rp_cpu_needs_gp;
- unsigned long n_rp_gp_completed;
- unsigned long n_rp_gp_started;
- unsigned long n_rp_nocb_defer_wakeup;
- unsigned long n_rp_need_nothing;
-
- /* 6) _rcu_barrier(), OOM callbacks, and expediting. */
+ /* 5) _rcu_barrier(), OOM callbacks, and expediting. */
struct rcu_head barrier_head;
#ifdef CONFIG_RCU_FAST_NO_HZ
struct rcu_head oom_head;
@@ -248,7 +237,7 @@ struct rcu_data {
atomic_long_t exp_workdone3; /* # done by others #3. */
int exp_dynticks_snap; /* Double-check need for IPI. */

- /* 7) Callback offloading. */
+ /* 6) Callback offloading. */
#ifdef CONFIG_RCU_NOCB_CPU
struct rcu_head *nocb_head; /* CBs waiting for kthread. */
struct rcu_head **nocb_tail;
@@ -275,7 +264,7 @@ struct rcu_data {
/* Leader CPU takes GP-end wakeups. */
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */

- /* 8) RCU CPU stall data. */
+ /* 7) RCU CPU stall data. */
unsigned int softirq_snap; /* Snapshot of softirq activity. */
/* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
struct irq_work rcu_iw; /* Check for non-irq activity. */
--
2.5.2