On Fri, Jul 24, 2015 at 7:46 AM, Cornelia Huck <cornelia.h...@de.ibm.com> wrote: > On Thu, 23 Jul 2015 21:29:05 +0200 > Christian Borntraeger <borntrae...@de.ibm.com> wrote: > >> Am 23.07.2015 um 21:25 schrieb Paolo Bonzini: >> > >> > >> > On 23/07/2015 21:19, Christian Borntraeger wrote: >> >> Am 23.07.2015 um 20:19 schrieb Paolo Bonzini: >> >>> >> >>> >> >>> On 23/07/2015 19:20, Paolo Bonzini wrote: >> >>>> >> >>>> >> >>>> On 23/07/2015 16:14, Cornelia Huck wrote: >> >>>>> (gdb) bt >> >>>>> #0 0x000003fffc5871b4 in pthread_cond_wait@@GLIBC_2.3.2 () >> >>>>> from /lib64/libpthread.so.0 >> >>>>> #1 0x000000008024cfca in qemu_cond_wait (cond=cond@entry=0x9717d950, >> >>>>> mutex=mutex@entry=0x9717d920) >> >>>>> at /data/git/yyy/qemu/util/qemu-thread-posix.c:132 >> >>>>> #2 0x000000008025e83a in rfifolock_lock (r=0x9717d920) >> >>>>> at /data/git/yyy/qemu/util/rfifolock.c:59 >> >>>>> #3 0x00000000801b78fa in aio_context_acquire (ctx=<optimized out>) >> >>>>> at /data/git/yyy/qemu/async.c:331 >> >>>>> #4 0x000000008007ceb4 in virtio_blk_data_plane_start (s=0x9717d710) >> >>>>> at /data/git/yyy/qemu/hw/block/dataplane/virtio-blk.c:285 >> >>>>> #5 0x000000008007c64a in virtio_blk_handle_output (vdev=<optimized >> >>>>> out>, >> >>>>> vq=<optimized out>) at /data/git/yyy/qemu/hw/block/virtio-blk.c:599 >> >>>>> #6 0x00000000801c56dc in qemu_iohandler_poll (pollfds=0x97142800, >> >>>>> ret=ret@entry=1) at /data/git/yyy/qemu/iohandler.c:126 >> >>>>> #7 0x00000000801c5178 in main_loop_wait (nonblocking=<optimized out>) >> >>>>> at /data/git/yyy/qemu/main-loop.c:494 >> >>>>> #8 0x0000000080013ee2 in main_loop () at /data/git/yyy/qemu/vl.c:1902 >> >>>>> #9 main (argc=<optimized out>, argv=<optimized out>, envp=<optimized >> >>>>> out>) >> >>>>> at /data/git/yyy/qemu/vl.c:4653 >> >>>>> >> >>>>> I've stripped down the setup to the following commandline: >> >>>>> >> >>>>> /data/git/yyy/qemu/build/s390x-softmmu/qemu-system-s390x -machine >> >>>>> s390-ccw-virtio-2.4,accel=kvm,usb=off -m 1024 -smp >> >>>>> 4,sockets=4,cores=1,threads=1 -nographic -drive >> >>>>> file=/dev/sda,if=none,id=drive-virtio-disk0,format=raw,serial=ccwzfcp1,cache=none,aio=native >> >>>>> -device >> >>>>> virtio-blk-ccw,scsi=off,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1,x-data-plane=on >> >>>> >> >>>> What's the backtrace like for the other threads? This is almost >> >>>> definitely a latent bug somewhere else. >> >>> >> >>> BTW, I can reproduce this---I'm asking because I cannot even attach gdb >> >>> to the hung process. >> >>> >> >>> The simplest workaround is to reintroduce commit a0710f7995 (iothread: >> >>> release iothread around aio_poll, 2015-02-20), though it also comes with >> >>> some risk. It avoids the bug because it limits the contention on the >> >>> RFifoLock. >> >> >> >> I can reproduce this with the following backtrace (with --enable-debug >> >> info added qemu is the tag v2.4.0-rc2) >> > >> > Can you check that cherry-picking a0710f7995 works for you? >> > >> >> Yes, this seems to help for me. Conny, can you verify? > > I can't reproduce the hang with this on top, so seems to help.
Thanks Christian and Cornelia. I'm sending a fix. Stefan