When the request free list is exhausted the coroutine waits on
q->free_req_queue for the next free request. Whenever a request is
completed a BH is scheduled to invoke nvme_free_req_queue_cb() and wake
up waiting coroutines.
1. nvme_get_free_req() waits for a free request:
while (q->free_req_head == -1) {
...
trace_nvme_free_req_queue_wait(q->s, q->index);
qemu_co_queue_wait(&q->free_req_queue, &q->lock);
...
}
2. nvme_free_req_queue_cb() wakes up the coroutine:
while (qemu_co_enter_next(&q->free_req_queue, &q->lock)) {
^--- infinite loop when free_req_head == -1
}
nvme_free_req_queue_cb() and the coroutine form an infinite loop when
q->free_req_head == -1. Fix this by checking q->free_req_head in
nvme_free_req_queue_cb(). If the free request list is exhausted, don't
wake waiting coroutines. Eventually an in-flight request will complete
and the BH will be scheduled again, guaranteeing forward progress.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20211208152246.244585-1-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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