[PATCH 2/2] sched/psi: convert trigger window/threshold to ns in u64

[Tao Cui]

From: Tao Cui <cuitao@xxxxxxxxxx>

psi_trigger_create() scales the trigger threshold and window from
microseconds to nanoseconds as

    t->threshold = threshold_us * NSEC_PER_USEC;
    t->win.size  = window_us   * NSEC_PER_USEC;

NSEC_PER_USEC is 1000L, so on 32-bit the multiply is done in 32 bits and
wraps for windows larger than ~4.29s (WINDOW_MAX_US is 10s): a 10s window
is stored as ~1.41s and the trigger fires much too eagerly.  Cast to u64
before multiplying.

Fixes: 0e94682b73bf ("psi: introduce psi monitor")
Signed-off-by: Tao Cui <cuitao@xxxxxxxxxx>
---
 kernel/sched/psi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 6514b44222cf..7fbe9b94fafa 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -1390,8 +1390,8 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, char *buf,
 
 	t->group = group;
 	t->state = state;
-	t->threshold = threshold_us * NSEC_PER_USEC;
-	t->win.size = window_us * NSEC_PER_USEC;
+	t->threshold = (u64)threshold_us * NSEC_PER_USEC;
+	t->win.size = (u64)window_us * NSEC_PER_USEC;
 	window_reset(&t->win, sched_clock(),
 			group->total[PSI_POLL][t->state], 0);
 
-- 
2.43.0