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author | Stefan Hajnoczi <stefanha@redhat.com> | 2021-12-08 15:22:46 +0000 |
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committer | Stefan Hajnoczi <stefanha@redhat.com> | 2021-12-09 09:19:49 +0000 |
commit | cf4fbc3030c974fff726756a7ceef8386cdf500b (patch) | |
tree | ca6d09351156c279e124629f084dbe6c2de64445 /block/nvme.c | |
parent | a3607def89f9cd68c1b994e1030527df33aa91d0 (diff) | |
download | qemu-cf4fbc3030c974fff726756a7ceef8386cdf500b.zip qemu-cf4fbc3030c974fff726756a7ceef8386cdf500b.tar.gz qemu-cf4fbc3030c974fff726756a7ceef8386cdf500b.tar.bz2 |
block/nvme: fix infinite loop in nvme_free_req_queue_cb()
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>
Diffstat (limited to 'block/nvme.c')
-rw-r--r-- | block/nvme.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/block/nvme.c b/block/nvme.c index e4f336d..fa360b9 100644 --- a/block/nvme.c +++ b/block/nvme.c @@ -206,8 +206,9 @@ static void nvme_free_req_queue_cb(void *opaque) NVMeQueuePair *q = opaque; qemu_mutex_lock(&q->lock); - while (qemu_co_enter_next(&q->free_req_queue, &q->lock)) { - /* Retry all pending requests */ + while (q->free_req_head != -1 && + qemu_co_enter_next(&q->free_req_queue, &q->lock)) { + /* Retry waiting requests */ } qemu_mutex_unlock(&q->lock); } |