[PATCH v4 tip/core/rcu 35/38] rcu-tasks: Add IPI failure count to statistics

paulmck
2020-04-15T18:21:13Z

This commit adds a failure-return count for smp_call_function_single(),
and adds this to the console messages for rcutorture writer stalls and at
the end of rcutorture testing.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/rcu/tasks.h | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 43cac4b..e600d29 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -32,6 +32,7 @@ typedef void (*postgp_func_t)(struct rcu_tasks *rtp);
* @gp_start: Most recent grace-period start in jiffies.
* @n_gps: Number of grace periods completed since boot.
* @n_ipis: Number of IPIs sent to encourage grace periods to end.
+ * @n_ipis_fails: Number of IPI-send failures.
* @pregp_func: This flavor's pre-grace-period function (optional).
* @pertask_func: This flavor's per-task scan function (optional).
* @postscan_func: This flavor's post-task scan function (optional).
@@ -51,6 +52,7 @@ struct rcu_tasks {
unsigned long gp_start;
unsigned long n_gps;
unsigned long n_ipis;
+ unsigned long n_ipis_fails;
struct task_struct *kthread_ptr;
rcu_tasks_gp_func_t gp_func;
pregp_func_t pregp_func;
@@ -290,12 +292,12 @@ static void __init rcu_tasks_bootup_oddness(void)
/* Dump out rcutorture-relevant state common to all RCU-tasks flavors. */
static void show_rcu_tasks_generic_gp_kthread(struct rcu_tasks *rtp, char *s)
{
- pr_info("%s: %s(%d) since %lu g:%lu i:%lu %c%c %s\n",
+ pr_info("%s: %s(%d) since %lu g:%lu i:%lu/%lu %c%c %s\n",
rtp->kname,
- tasks_gp_state_getname(rtp),
- data_race(rtp->gp_state),
+ tasks_gp_state_getname(rtp), data_race(rtp->gp_state),
jiffies - data_race(rtp->gp_jiffies),
- data_race(rtp->n_gps), data_race(rtp->n_ipis),
+ data_race(rtp->n_gps),
+ data_race(rtp->n_ipis_fails), data_race(rtp->n_ipis),
".k"[!!data_race(rtp->kthread_ptr)],
".C"[!!data_race(rtp->cbs_head)],
s);
@@ -905,6 +907,7 @@ static void trc_wait_for_one_reader(struct task_struct *t,
trc_read_check_handler, t, 0)) {
// Just in case there is some other reason for
// failure than the target CPU being offline.
+ rcu_tasks_trace.n_ipis_fails++;
per_cpu(trc_ipi_to_cpu, cpu) = false;
t->trc_ipi_to_cpu = cpu;
if (atomic_dec_and_test(&trc_n_readers_need_end)) {
--
2.9.5