Re: [Qemu-devel] [PATCH] vl: take iothread lock very early

[Oliver Francke <Oliver.Francke@filoo.de>]

Hi all,

just brief, this small one breaks my qemu-system-x86_64 with:

     qemu: qemu_cond_wait: Operation not permitted

My most complete qemu-starter:

/usr/local/qemu-2.3.0/bin/qemu-system-x86_64 -daemonize -usbdevice 
tablet -enable-kvm -pidfile /var/run/qemu-server/3371.pid -monitor 
unix:/var/run/qemu-server/3371.mon,server,nowait -vnc 
unix:/var/run/qemu-server/3371.vnc,password -qmp 
unix:/var/run/qemu-server/3371.qmp,server,nowait -nodefaults -serial 
none -parallel none -device rtl8139,mac=00:F1:70:00:D2:B0,netdev=vlan0d0 
-netdev 
type=tap,id=vlan0d0,ifname=tap3371i0d0,script=/etc/fcms/add_if.sh,downscript=/etc/fcms/downscript.sh 
-name 1155823384-7 -vga cirrus -k de -smp sockets=1,cores=1 -m 512 
-device virtio-blk-pci,drive=virtio0 -drive 
format=raw,file=rbd:4/vm-3371-disk-1.rbd:rbd_cache=true:rbd_cache_size=16777216:rbd_cache_max_dirty=12582912:rbd_cache_target_dirty=8388608,cache=writeback,if=none,id=virtio0,media=disk,index=0 
-drive 
format=raw,file=rbd:4/vm-3371-swap-1.rbd:rbd_cache=true:rbd_cache_size=16777216:rbd_cache_max_dirty=12582912:rbd_cache_target_dirty=8388608,cache=writeback,if=virtio,media=disk,index=1 
-drive if=ide,media=cdrom,id=ide1-cd0,readonly=on -drive 
if=ide,media=cdrom,id=ide1-cd1,readonly=on -boot order=dc

Up to the former commit everything works well as expected.

Hope it helps,

Oliver.


On 03/03/2015 11:36 AM, Paolo Bonzini wrote:
> If the iothread lock isn't taken by the main thread, the RCU callbacks
> might run concurrently with the main thread.  QEMU's not ready for that.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   vl.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/vl.c b/vl.c
> index 09693f5..d743727 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -2763,6 +2763,9 @@ int main(int argc, char **argv, char **envp)
>       FILE *vmstate_dump_file = NULL;
>       Error *main_loop_err = NULL;
>   
> +    qemu_init_cpu_loop();
> +    qemu_mutex_lock_iothread();
> +
>       atexit(qemu_run_exit_notifiers);
>       error_set_progname(argv[0]);
>       qemu_init_exec_dir(argv[0]);
> @@ -4098,9 +4101,6 @@ int main(int argc, char **argv, char **envp)
>   
>       os_set_line_buffering();
>   
> -    qemu_init_cpu_loop();
> -    qemu_mutex_lock_iothread();
> -
>   #ifdef CONFIG_SPICE
>       /* spice needs the timers to be initialized by this point */
>       qemu_spice_init();


-- 

Oliver Francke

filoo GmbH
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