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fix(core): prevent busy-loop in complete handler when HW stalls #16

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fix(core): prevent busy-loop in complete handler when HW stalls #16

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11 changes: 11 additions & 0 deletions core_common.c
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Original file line number Diff line number Diff line change
Expand Up @@ -183,12 +183,14 @@ int mx_complete_handler(void *arg)
while (!kthread_should_stop()) {
bool zombie_only = (atomic_read(&q->wait_count) > 0 &&
atomic_read(&q->zombie_wait_count) == atomic_read(&q->wait_count));
bool popped_any = false;

__swait_event_interruptible_timeout(q->cq_wait,
atomic_read(&q->wait_count) - atomic_read(&q->zombie_wait_count) > 0,
zombie_only ? ZOMBIE_POLL_INTERVAL_MSEC : POLLING_INTERVAL_MSEC);

while (ops->is_popable(q)) {
popped_any = true;
ops->pop_completion(q, &info);

transfer = find_transfer_by_id(info.id);
Expand Down Expand Up @@ -217,6 +219,15 @@ int mx_complete_handler(void *arg)

if (ops->post_complete)
ops->post_complete(q);

/*
* If completions were expected but none arrived, sleep to
* avoid busy-looping (the swait above does not sleep when
* its condition is already true).
*/
if (!popped_any)
schedule_timeout_interruptible(
msecs_to_jiffies(POLLING_INTERVAL_MSEC));
}

return 0;
Expand Down