> I *think* the second patch also fixes the hangs on backup abort that I and > Dietmar noticed in v1, but I'm not sure, they we're somewhat intermittent > before too.
After more test, I am 100% sure the bug (or another one) is still there. Here is how to trigger: 1. use latest qemu sources from githup 2. apply those 3 patches from Stefan 2. create a VM with virtio-scsis-single drive using io-thread 3. inside VM install Debian buster 4. inside VM, run "stress -d 5" Then run a series of backups, aborting them after a few seconds: # start loop qmp: { "execute": "drive-backup", "arguments": { "device": "drive-scsi0", "sync": "full", "target": "backup-scsi0.raw" } } sleep 3 second qmp: { "execute": "'block-job-cancel", "arguments": { "device": "drive-scsi0" } } # end loop After several iterations (mostly < 50) the VM freezes (this time somewhere inside drive_backup_prepare): (gdb) bt #0 0x00007f61ea09e916 in __GI_ppoll (fds=0x7f6158130c40, nfds=2, timeout=<optimized out>, timeout@entry=0x0, sigmask=sigmask@entry=0x0) at ../sysdeps/unix/sysv/linux/ppoll.c:39 #1 0x000055f708401c79 in ppoll (__ss=0x0, __timeout=0x0, __nfds=<optimized out>, __fds=<optimized out>) at /usr/include/x86_64-linux-gnu/bits/poll2.h:77 #2 0x000055f708401c79 in qemu_poll_ns (fds=<optimized out>, nfds=<optimized out>, timeout=timeout@entry=-1) at util/qemu-timer.c:335 #3 0x000055f708404461 in fdmon_poll_wait (ctx=0x7f61dcd05e80, ready_list=0x7ffc4e7fbde8, timeout=-1) at util/fdmon-poll.c:79 #4 0x000055f708403a47 in aio_poll (ctx=0x7f61dcd05e80, blocking=blocking@entry=true) at util/aio-posix.c:589 #5 0x000055f708364c03 in bdrv_do_drained_begin (poll=<optimized out>, ignore_bds_parents=false, parent=0x0, recursive=false, bs=0x7f61dcd4c500) at block/io.c:429 #6 0x000055f708364c03 in bdrv_do_drained_begin (bs=0x7f61dcd4c500, recursive=<optimized out>, parent=0x0, ignore_bds_parents=<optimized out>, poll=<optimized out>) at block/io.c:395 #7 0x000055f7081016f9 in drive_backup_prepare (common=0x7f61d9a0c280, errp=0x7ffc4e7fbf28) at blockdev.c:1755 #8 0x000055f708103e6a in qmp_transaction (dev_list=dev_list@entry=0x7ffc4e7fbfa0, has_props=has_props@entry=false, props=0x7f61d9a304e8, props@entry=0x0, errp=errp@entry=0x7ffc4e7fbfd8) at blockdev.c:2401 #9 0x000055f708105322 in blockdev_do_action (errp=0x7ffc4e7fbfd8, action=0x7ffc4e7fbf90) at blockdev.c:1054 #10 0x000055f708105322 in qmp_drive_backup (backup=backup@entry=0x7ffc4e7fbfe0, errp=errp@entry=0x7ffc4e7fbfd8) at blockdev.c:3129 #11 0x000055f7082c0101 in qmp_marshal_drive_backup (args=<optimized out>, ret=<optimized out>, errp=0x7ffc4e7fc0b8) at qapi/qapi-commands-block-core.c:555 #12 0x000055f7083b7338 in qmp_dispatch (cmds=0x55f708904000 <qmp_commands>, request=<optimized out>, allow_oob=<optimized out>) at qapi/qmp-dispatch.c:155 #13 0x000055f7082a1bd1 in monitor_qmp_dispatch (mon=0x7f61dcd15d80, req=<optimized out>) at monitor/qmp.c:145 #14 0x000055f7082a23ba in monitor_qmp_bh_dispatcher (data=<optimized out>) at monitor/qmp.c:234 #15 0x000055f708400205 in aio_bh_call (bh=0x7f61dd28f960) at util/async.c:164 #16 0x000055f708400205 in aio_bh_poll (ctx=ctx@entry=0x7f61dd33ef80) at util/async.c:164 #17 0x000055f70840388e in aio_dispatch (ctx=0x7f61dd33ef80) at util/aio-posix.c:380 #18 0x000055f7084000ee in aio_ctx_dispatch (source=<optimized out>, callback=<optimized out>, user_data=<optimized out>) at util/async.c:298 #19 0x00007f61ec069f2e in g_main_context_dispatch () at /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0 #20 0x000055f708402af8 in glib_pollfds_poll () at util/main-loop.c:219 #21 0x000055f708402af8 in os_host_main_loop_wait (timeout=<optimized out>) at util/main-loop.c:242 #22 0x000055f708402af8 in main_loop_wait (nonblocking=nonblocking@entry=0) at util/main-loop.c:518 #23 0x000055f70809e589 in qemu_main_loop () at /home/dietmar/pve5-devel/mirror_qemu/softmmu/vl.c:1665 #24 0x000055f707fa2c3e in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at /home/dietmar/pve5-devel/mirror_qemu/softmmu/main.c:49