Re: [Qemu-devel] [PULL for-2.5 2/4] block: Don't wait serialising for non-COR read requests

[Cornelia Huck <cornelia.huck@de.ibm.com>]

On Thu,  3 Dec 2015 13:00:00 +0800
Stefan Hajnoczi <stefanha@redhat.com> wrote:

> From: Fam Zheng <famz@redhat.com>
> 
> The assertion problem was noticed in 06c3916b35a, but it wasn't
> completely fixed, because even though the req is not marked as
> serialising, it still gets serialised by wait_serialising_requests
> against other serialising requests, which could lead to the same
> assertion failure.
> 
> Fix it by even more explicitly skipping the serialising for this
> specific case.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> Message-id: 1448962590-2842-2-git-send-email-famz@redhat.com
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  block/backup.c        |  2 +-
>  block/io.c            | 12 +++++++-----
>  include/block/block.h |  4 ++--
>  trace-events          |  2 +-
>  4 files changed, 11 insertions(+), 9 deletions(-)

This one causes segfaults for me:

Program received signal SIGSEGV, Segmentation fault.
bdrv_is_inserted (bs=0x800000000000) at /data/git/yyy/qemu/block.c:3071
3071	    if (!drv) {

(gdb) bt
#0  bdrv_is_inserted (bs=0x800000000000) at /data/git/yyy/qemu/block.c:3071
#1  0x0000000080216974 in blk_is_inserted (blk=<optimized out>)
    at /data/git/yyy/qemu/block/block-backend.c:986
#2  0x00000000802169c6 in blk_is_available (blk=blk@entry=0x3ffb17e7960)
    at /data/git/yyy/qemu/block/block-backend.c:991
#3  0x0000000080216d12 in blk_check_byte_request (blk=blk@entry=0x3ffb17e7960, 
    offset=offset@entry=4928966656, size=16384)
    at /data/git/yyy/qemu/block/block-backend.c:558
#4  0x0000000080216df2 in blk_check_request (blk=blk@entry=0x3ffb17e7960, 
    sector_num=sector_num@entry=9626888, nb_sectors=nb_sectors@entry=32)
    at /data/git/yyy/qemu/block/block-backend.c:589
#5  0x0000000080217ee8 in blk_aio_readv (blk=0x3ffb17e7960, sector_num=
    9626888, iov=0x8098c658, nb_sectors=<optimized out>, cb=
    0x80081150 <virtio_blk_rw_complete>, opaque=0x80980620)
    at /data/git/yyy/qemu/block/block-backend.c:727
#6  0x000000008008186e in submit_requests (niov=<optimized out>, 
    num_reqs=<optimized out>, start=<optimized out>, mrb=<optimized out>, 
    blk=<optimized out>) at /data/git/yyy/qemu/hw/block/virtio-blk.c:366
#7  virtio_blk_submit_multireq (mrb=<optimized out>, blk=<optimized out>)
    at /data/git/yyy/qemu/hw/block/virtio-blk.c:444
#8  virtio_blk_submit_multireq (blk=0x3ffb17e7960, mrb=0x3ffffffeb58)
    at /data/git/yyy/qemu/hw/block/virtio-blk.c:389
#9  0x00000000800823ee in virtio_blk_handle_output (vdev=<optimized out>, 
    vq=<optimized out>) at /data/git/yyy/qemu/hw/block/virtio-blk.c:615
#10 0x00000000801e367e in aio_dispatch (ctx=0x80918520)
    at /data/git/yyy/qemu/aio-posix.c:326
#11 0x00000000801d28b0 in aio_ctx_dispatch (source=<optimized out>, 
    callback=<optimized out>, user_data=<optimized out>)
    at /data/git/yyy/qemu/async.c:231
#12 0x000003fffd36a05a in g_main_context_dispatch ()
   from /lib64/libglib-2.0.so.0
#13 0x00000000801e0ffa in glib_pollfds_poll ()
    at /data/git/yyy/qemu/main-loop.c:211
#14 os_host_main_loop_wait (timeout=<optimized out>)
    at /data/git/yyy/qemu/main-loop.c:256
#15 main_loop_wait (nonblocking=<optimized out>)
    at /data/git/yyy/qemu/main-loop.c:504
#16 0x00000000800148a6 in main_loop () at /data/git/yyy/qemu/vl.c:1923
#17 main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>)
    at /data/git/yyy/qemu/vl.c:4684

Relevant part of command line:

-drive file=/dev/sda,if=none,id=drive-virtio-disk0,format=raw,serial=ccwzfcp1,cache=none -device virtio-blk-ccw,devno=fe.0.0001,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1,scsi=off