From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
commit c58d80f52 ("usb: musb: Ensure that cppi41 timer gets armed on
premature DMA TX irq") fixed hrtimer scheduling bug. There is one left
which does not trigger that often.
The following scenario is still possible:
lock(&x->lock);
hrtimer_start(&x->t);
unlock(&x->lock);
expires:
t->function();
lock(&x->lock);
lock(&x->lock); if (!hrtimer_queued(&x->t))
hrtimer_start(&x->t);
unlock(&x->lock);
if (!list_empty(x->early_tx_list))
ret = HRTIMER_RESTART;
-> hrtimer_forward_now(...)
} else
ret = HRTIMER_NORESTART;
unlock(&x->lock);
and the timer callback returns HRTIMER_RESTART for an armed timer. This
is wrong and we run into the BUG_ON() in __run_hrtimer().
This can happens on SMP or PREEMPT-RT.
The patch fixes the problem by only starting the timer if the timer is
not yet queued.
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Torben Hohn <torbenh@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
[bigeasy: collected information and created a patch + description based
on it]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
drivers/usb/musb/musb_cppi41.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/musb/musb_cppi41.c b/drivers/usb/musb/musb_cppi41.c
index 3ee133f..013fd1c 100644
--- a/drivers/usb/musb/musb_cppi41.c
+++ b/drivers/usb/musb/musb_cppi41.c
@@ -209,7 +209,8 @@ static enum hrtimer_restart cppi41_recheck_tx_req(struct hrtimer *timer)
}
}
- if (!list_empty(&controller->early_tx_list)) {
+ if (!list_empty(&controller->early_tx_list) &&
+ !hrtimer_is_queued(&controller->early_tx)) {
ret = HRTIMER_RESTART;
hrtimer_forward_now(&controller->early_tx,
ktime_set(0, 50 * NSEC_PER_USEC));
--
1.9.3
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