On Tue, 03/13 17:38, sochin.jiang wrote: > > Hi, guys, > > Recently, I encountered an IO hang problem in occasion which I cannot > reproduce it now. > > I analyzed this problem carefully, the critical stack is as following: > > > After reading the codes in linux-aio.c(see ioq_submit() function), I found > two situations could lead us here. > > 1) no AIOs are in flight(s->ioq.in_flight is 0) and another call to io_submit > returns -EAGAIN
So if there is no inflight I/O, why it would return -EAGAIN? The tricky thing here is that since we're not expecting a completion, when should we retry? > > 2) no AIOs are in flight(s->ioq.in_flight is 0) and s->io_q.pending IOs reach > to MAX_EVENTS at once I don't understand this case. We have, len = 0; QSIMPLEQ_FOREACH(aiocb, &s->io_q.pending, next) { iocbs[len++] = &aiocb->iocb; if (s->io_q.in_flight + len >= MAX_EVENTS) { break; } } ret = io_submit(s->ctx, len, iocbs); If in_flight is 0, only (MAX_EVENTS - 1) requests can be added to iocbs, so io_submit shouldn't return -EAGAIN. > > In both the two situations above, the do{...}while loop breaks out and set > s->io_q.blocked true. > > After that, AIO completion callback will never be called, ioq_submit() > either, all pended requests will hang. > > > Is there a proper way we can fix this while do not affect(stuck) the guest ? Fam