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Subject[PATCH] psi: fix possible trigger missing in the window
Date
From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>

There could be missing wake up if the rest of the window remain the
same stall states as the polling_total updates for every polling_min_period.

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
---
include/linux/psi_types.h | 2 ++
kernel/sched/psi.c | 30 ++++++++++++++++++------------
2 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h
index 0a23300..9533d2e 100644
--- a/include/linux/psi_types.h
+++ b/include/linux/psi_types.h
@@ -132,6 +132,8 @@ struct psi_trigger {

/* Refcounting to prevent premature destruction */
struct kref refcount;
+
+ bool new_stall;
};

struct psi_group {
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 1652f2b..402718c 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -458,9 +458,12 @@ static void psi_avgs_work(struct work_struct *work)
static void window_reset(struct psi_window *win, u64 now, u64 value,
u64 prev_growth)
{
+ struct psi_trigger *t = container_of(win, struct psi_trigger, win);
+
win->start_time = now;
win->start_value = value;
win->prev_growth = prev_growth;
+ t->new_stall = false;
}

/*
@@ -515,7 +518,6 @@ static void init_triggers(struct psi_group *group, u64 now)
static u64 update_triggers(struct psi_group *group, u64 now)
{
struct psi_trigger *t;
- bool new_stall = false;
u64 *total = group->total[PSI_POLL];

/*
@@ -523,19 +525,26 @@ static u64 update_triggers(struct psi_group *group, u64 now)
* watchers know when their specified thresholds are exceeded.
*/
list_for_each_entry(t, &group->triggers, node) {
- u64 growth;
-
/* Check for stall activity */
if (group->polling_total[t->state] == total[t->state])
continue;

/*
- * Multiple triggers might be looking at the same state,
- * remember to update group->polling_total[] once we've
- * been through all of them. Also remember to extend the
- * polling time if we see new stall activity.
+ * update the trigger if there is new stall which will be
+ * reset when run out of the window
*/
- new_stall = true;
+ t->new_stall = true;
+
+ memcpy(&group->polling_total[t->state], &total[t->state],
+ sizeof(group->polling_total[t->state]));
+ }
+
+ list_for_each_entry(t, &group->triggers, node) {
+ u64 growth;
+
+ /* check if new stall happened during this window*/
+ if (!t->new_stall)
+ continue;

/* Calculate growth since last update */
growth = window_update(&t->win, now, total[t->state]);
@@ -552,10 +561,6 @@ static u64 update_triggers(struct psi_group *group, u64 now)
t->last_event_time = now;
}

- if (new_stall)
- memcpy(group->polling_total, total,
- sizeof(group->polling_total));
-
return now + group->poll_min_period;
}

@@ -1152,6 +1157,7 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group,
t->last_event_time = 0;
init_waitqueue_head(&t->event_wait);
kref_init(&t->refcount);
+ t->new_stall = false;

mutex_lock(&group->trigger_lock);

--
1.9.1
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