Re: [PATCH v4 09/23] job: call job_enter from job_pause

[Max Reitz]

On 16.01.21 22:46, Vladimir Sementsov-Ogievskiy wrote:
> If main job coroutine called job_yield (while some background process
> is in progress), we should give it a chance to call job_pause_point().
> It will be used in backup, when moved on async block-copy.
>
> Note, that job_user_pause is not enough: we want to handle
> child_job_drained_begin() as well, which call job_pause().
>
> Still, if job is already in job_do_yield() in job_pause_point() we
> should not enter it.
>
> iotest 109 output is modified: on stop we do bdrv_drain_all() which now
> triggers job pause immediately (and pause after ready is standby).
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>   job.c                      |  3 +++
>   tests/qemu-iotests/109.out | 24 ++++++++++++++++++++++++
>   2 files changed, 27 insertions(+)

While looking into

https://lists.gnu.org/archive/html/qemu-block/2021-04/msg00035.html

I noticed this:

$ ./qemu-img create -f raw src.img 1G
$ ./qemu-img create -f raw dst.img 1G

$ (echo '
    {"execute":"qmp_capabilities"}
    {"execute":"blockdev-mirror",
     "arguments":{"job-id":"mirror",
                  "device":"source",
                  "target":"target",
                  "sync":"full",
                  "filter-node-name":"mirror-top"}}
'; sleep 3; echo '
    {"execute":"human-monitor-command",
     "arguments":{"command-line":
                  "qemu-io mirror-top \"write 0 1G\""}}') \
| x86_64-softmmu/qemu-system-x86_64 \
    -qmp stdio \
    -blockdev file,node-name=source,filename=src.img \
    -blockdev file,node-name=target,filename=dst.img \
    -object iothread,id=iothr0 \
    -device virtio-blk,drive=source,iothread=iothr0

Before this commit, qemu-io returned an error that there is a permission 
conflict with virtio-blk.  After this commit, there is an abort (“qemu: 
qemu_mutex_unlock_impl: Operation not permitted”):

#0  0x00007f8445a4eef5 in raise () at /usr/lib/libc.so.6
#1  0x00007f8445a38862 in abort () at /usr/lib/libc.so.6
#2  0x000055fbb14a36bf in error_exit
    (err=<optimized out>, msg=msg@entry=0x55fbb1634790 <__func__.27> 
"qemu_mutex_unlock_impl")
    at ../util/qemu-thread-posix.c:37
#3  0x000055fbb14a3bc3 in qemu_mutex_unlock_impl
    (mutex=mutex@entry=0x55fbb25ab6e0, file=file@entry=0x55fbb1636957 
"../util/async.c", line=line@entry=650)
    at ../util/qemu-thread-posix.c:109
#4  0x000055fbb14b2e75 in aio_context_release 
(ctx=ctx@entry=0x55fbb25ab680) at ../util/async.c:650
#5  0x000055fbb13d2029 in bdrv_do_drained_begin
    (bs=bs@entry=0x55fbb3a87000, recursive=recursive@entry=false, 
parent=parent@entry=0x0, 
ignore_bds_parents=ignore_bds_parents@entry=false, poll=poll@entry=true) 
at ../block/io.c:441
#6  0x000055fbb13d2192 in bdrv_do_drained_begin
    (poll=true, ignore_bds_parents=false, parent=0x0, recursive=false, 
bs=0x55fbb3a87000) at ../block/io.c:448
#7  0x000055fbb13c71a7 in blk_drain (blk=0x55fbb26c5a00) at 
../block/block-backend.c:1718
#8  0x000055fbb13c8bbd in blk_unref (blk=0x55fbb26c5a00) at 
../block/block-backend.c:498
#9  blk_unref (blk=0x55fbb26c5a00) at ../block/block-backend.c:491
#10 0x000055fbb1024863 in hmp_qemu_io (mon=0x7fffaf3fc7d0, 
qdict=<optimized out>)
    at ../block/monitor/block-hmp-cmds.c:628

Can you make anything out of this?

Max