Comment 2 for bug 1878255

(gdb) fr 4
#4 0x000056378b63e3aa in ide_reset (s=0x56378d64d730) at hw/ide/core.c:1318
1318 blk_aio_cancel(s->pio_aiocb);
(gdb) p *s->pio_aiocb
$1 = {aiocb_info = 0x56378bb55520 <blk_aio_em_aiocb_info>, bs = 0x0, cb = 0x56378b63d9f8 <ide_flush_cb>, opaque = 0x56378d64d730, refcnt = 2}

void bdrv_aio_cancel(BlockAIOCB *acb)
{
    qemu_aio_ref(acb);
    bdrv_aio_cancel_async(acb);
    while (acb->refcnt > 1) {
        if (acb->aiocb_info->get_aio_context) {
            ...
        } else if (acb->bs) {
            ...
        } else {
            abort();
        }