Re: [Qemu-devel] [PATCH 0/6] virtio: refactor host notifiers

[TU BO <tubo@linux.vnet.ibm.com>]

Hi Cornelia:

I got two crash with qemu master + "[PATCH 0/6] virtio: refactor host 
notifiers",

I can get first crash very often.
(gdb) bt
#0  blk_aio_read_entry (opaque=0x0) at block/block-backend.c:922
#1  0x000002aa17a65f0e in coroutine_trampoline (i0=<optimized out>, 
i1=-1677713216) at util/coroutine-ucontext.c:78
#2  0x000003ffabfd150a in __makecontext_ret () from /lib64/libc.so.6
(gdb) list
917    static void blk_aio_read_entry(void *opaque)
918    {
919        BlkAioEmAIOCB *acb = opaque;
920        BlkRwCo *rwco = &acb->rwco;
921
922        rwco->ret = blk_co_preadv(rwco->blk, rwco->offset, 
rwco->qiov->size,
923                                  rwco->qiov, rwco->flags);
924        blk_aio_complete(acb);
925    }


For 2nd crash,  I just saw it once, and didn't reproduce it later.
(gdb) bt
#0  ioq_submit (s=s@entry=0x2aa3fe2cc80) at block/linux-aio.c:197
#1  0x000002aa3f645b36 in qemu_laio_completion_bh (opaque=0x2aa3fe2cc80) 
at block/linux-aio.c:143
#2  0x000002aa3f5ffbf0 in aio_bh_call (bh=<optimized out>) at async.c:65
#3  aio_bh_poll (ctx=0x2aa3fdf7e00) at async.c:93
#4  0x000002aa3f60a51e in aio_dispatch (ctx=ctx@entry=0x2aa3fdf7e00) at 
aio-posix.c:306
#5  0x000002aa3f60a7ca in aio_poll (ctx=0x2aa3fdf7e00, 
blocking=<optimized out>) at aio-posix.c:475
#6  0x000002aa3f53903c in iothread_run (opaque=0x2aa3fdf7220) at 
iothread.c:46
#7  0x000003ffa86084c6 in start_thread () from /lib64/libpthread.so.0
#8  0x000003ffa7c82ec2 in thread_start () from /lib64/libc.so.6
(gdb) list
192        struct iocb *iocbs[MAX_QUEUED_IO];
193        QSIMPLEQ_HEAD(, qemu_laiocb) completed;
194
195        do {
196            len = 0;
197            QSIMPLEQ_FOREACH(aiocb, &s->io_q.pending, next) {
198                iocbs[len++] = &aiocb->iocb;
199                if (len == MAX_QUEUED_IO) {
200                    break;
201                }


On 16/3/25 上午12:15, Cornelia Huck wrote:
> Here's the next version of my refactoring of the virtio host notifiers.
> This one actually survives a bit of testing for me (reboot loop).
>
> As this patchset fixes a latent bug exposed by the recent dataplane
> changes (we have a deassigned ioeventfd for a short period of time
> during dataplane start, which leads to the virtqueue handler being
> called in both the vcpu thread and the iothread simultaneously), I'd
> like to see this in 2.6.
>
> Changes from RFC:
> - Fixed some silly errors (checking for !disabled instead of disabled,
>    virtio_ccw_stop_ioeventfd() calling virtio_bus_start_ioeventfd()).
> - Completely reworked set_host_notifier(): We only want to set/unset
>    the actual handler function and don't want to do anything to the
>    ioeventfd backing, so reduce the function to actually doing only
>    that.
> - With the change above, we can lose the 'assign' parameter in
>    virtio_bus_stop_ioeventfd() again.
> - Added more comments that hopefully make it clearer what is going on.
>
> I'd appreciate it if people could give it some testing; I'll be back
> to look at the fallout after Easter.
>
> Cornelia Huck (6):
>    virtio-bus: common ioeventfd infrastructure
>    virtio-bus: have callers tolerate new host notifier api
>    virtio-ccw: convert to ioeventfd callbacks
>    virtio-pci: convert to ioeventfd callbacks
>    virtio-mmio: convert to ioeventfd callbacks
>    virtio-bus: remove old set_host_notifier callback
>
>   hw/block/dataplane/virtio-blk.c |   6 +-
>   hw/s390x/virtio-ccw.c           | 133 ++++++++++++++--------------------------
>   hw/scsi/virtio-scsi-dataplane.c |   9 ++-
>   hw/virtio/vhost.c               |  13 ++--
>   hw/virtio/virtio-bus.c          | 132 +++++++++++++++++++++++++++++++++++++++
>   hw/virtio/virtio-mmio.c         | 128 +++++++++++++-------------------------
>   hw/virtio/virtio-pci.c          | 124 +++++++++++++------------------------
>   include/hw/virtio/virtio-bus.h  |  31 +++++++++-
>   8 files changed, 303 insertions(+), 273 deletions(-)
>