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[Qemu-devel] another locking issue in current dataplane code?
From: |
Christian Borntraeger |
Subject: |
[Qemu-devel] another locking issue in current dataplane code? |
Date: |
Mon, 07 Jul 2014 13:58:01 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 |
Folks,
with current 2.1-rc0 (
+ dataplane: do not free VirtQueueElement in vring_push()
+ virtio-blk: avoid dataplane VirtIOBlockReq early free
+ some not-ready yet s390 patches for migration
)
I still having issues with dataplane during managedsave (without dataplane
everything seems to work fine):
With 1 CPU and 1 disk (and some workload, e.g. a simple dd on the disk) I get:
Thread 3 (Thread 0x3fff90fd910 (LWP 27218)):
#0 0x000003fffcdb7ba0 in __lll_lock_wait () from /lib64/libpthread.so.0
#1 0x000003fffcdbac0c in __pthread_mutex_cond_lock () from
/lib64/libpthread.so.0
#2 0x000003fffcdb399a in pthread_cond_wait@@GLIBC_2.3.2 () from
/lib64/libpthread.so.0
#3 0x00000000801fff06 in qemu_cond_wait (cond=<optimized out>, address@hidden
<qemu_global_mutex>) at /home/cborntra/REPOS/qemu/util/qemu-thread-posix.c:135
#4 0x00000000800472f4 in qemu_kvm_wait_io_event (cpu=<optimized out>) at
/home/cborntra/REPOS/qemu/cpus.c:843
#5 qemu_kvm_cpu_thread_fn (arg=0x809ad6b0) at
/home/cborntra/REPOS/qemu/cpus.c:879
#6 0x000003fffcdaf412 in start_thread () from /lib64/libpthread.so.0
#7 0x000003fffba350ae in thread_start () from /lib64/libc.so.6
Thread 2 (Thread 0x3fff88fd910 (LWP 27219)):
#0 0x000003fffba2a8e0 in ppoll () from /lib64/libc.so.6
#1 0x00000000801af250 in ppoll (__ss=0x0, __timeout=0x0, __nfds=<optimized
out>, __fds=<optimized out>) at /usr/include/bits/poll2.h:77
#2 qemu_poll_ns (address@hidden, address@hidden, timeout=-1) at
/home/cborntra/REPOS/qemu/qemu-timer.c:314
#3 0x00000000801b0702 in aio_poll (ctx=0x807f2230, address@hidden) at
/home/cborntra/REPOS/qemu/aio-posix.c:221
#4 0x00000000800be3c4 in iothread_run (opaque=0x807f20d8) at
/home/cborntra/REPOS/qemu/iothread.c:41
#5 0x000003fffcdaf412 in start_thread () from /lib64/libpthread.so.0
#6 0x000003fffba350ae in thread_start () from /lib64/libc.so.6
Thread 1 (Thread 0x3fff9c529b0 (LWP 27215)):
#0 0x000003fffcdb38f0 in pthread_cond_wait@@GLIBC_2.3.2 () from
/lib64/libpthread.so.0
#1 0x00000000801fff06 in qemu_cond_wait (address@hidden, address@hidden) at
/home/cborntra/REPOS/qemu/util/qemu-thread-posix.c:135
#2 0x0000000080212906 in rfifolock_lock (address@hidden) at
/home/cborntra/REPOS/qemu/util/rfifolock.c:59
#3 0x000000008019e536 in aio_context_acquire (address@hidden) at
/home/cborntra/REPOS/qemu/async.c:295
#4 0x00000000801a34e6 in bdrv_drain_all () at
/home/cborntra/REPOS/qemu/block.c:1907
#5 0x0000000080048e24 in do_vm_stop (state=RUN_STATE_PAUSED) at
/home/cborntra/REPOS/qemu/cpus.c:538
#6 vm_stop (address@hidden) at /home/cborntra/REPOS/qemu/cpus.c:1221
#7 0x00000000800e6338 in qmp_stop (address@hidden) at
/home/cborntra/REPOS/qemu/qmp.c:98
#8 0x00000000800e1314 in qmp_marshal_input_stop (mon=<optimized out>,
qdict=<optimized out>, ret=<optimized out>) at qmp-marshal.c:2806
#9 0x000000008004b91a in qmp_call_cmd (cmd=<optimized out>, params=0x8096cf50,
mon=0x8080b8a0) at /home/cborntra/REPOS/qemu/monitor.c:5038
#10 handle_qmp_command (parser=<optimized out>, tokens=<optimized out>) at
/home/cborntra/REPOS/qemu/monitor.c:5104
#11 0x00000000801faf16 in json_message_process_token (lexer=0x8080b7c0,
token=0x808f2610, type=<optimized out>, x=<optimized out>, y=6) at
/home/cborntra/REPOS/qemu/qobject/json-streamer.c:87
#12 0x0000000080212bac in json_lexer_feed_char (address@hidden, ch=<optimized
out>, address@hidden) at /home/cborntra/REPOS/qemu/qobject/json-lexer.c:303
#13 0x0000000080212cfe in json_lexer_feed (lexer=0x8080b7c0, buffer=<optimized
out>, size=<optimized out>) at
/home/cborntra/REPOS/qemu/qobject/json-lexer.c:356
#14 0x00000000801fb10e in json_message_parser_feed (parser=<optimized out>,
buffer=<optimized out>, size=<optimized out>) at
/home/cborntra/REPOS/qemu/qobject/json-streamer.c:110
#15 0x0000000080049f28 in monitor_control_read (opaque=<optimized out>,
buf=<optimized out>, size=<optimized out>) at
/home/cborntra/REPOS/qemu/monitor.c:5125
#16 0x00000000800c8636 in qemu_chr_be_write (len=1, buf=0x3ffffa9e010
"}[B\377\373\251\372\b", s=0x807f5af0) at
/home/cborntra/REPOS/qemu/qemu-char.c:213
#17 tcp_chr_read (chan=<optimized out>, cond=<optimized out>,
opaque=0x807f5af0) at /home/cborntra/REPOS/qemu/qemu-char.c:2690
#18 0x000003fffcc9f05a in g_main_context_dispatch () from
/lib64/libglib-2.0.so.0
#19 0x00000000801ae3e0 in glib_pollfds_poll () at
/home/cborntra/REPOS/qemu/main-loop.c:190
#20 os_host_main_loop_wait (timeout=<optimized out>) at
/home/cborntra/REPOS/qemu/main-loop.c:235
#21 main_loop_wait (nonblocking=<optimized out>) at
/home/cborntra/REPOS/qemu/main-loop.c:484
#22 0x00000000800169e2 in main_loop () at /home/cborntra/REPOS/qemu/vl.c:2024
#23 main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at
/home/cborntra/REPOS/qemu/vl.c:4551
Now. If aio_poll never returns, we have a deadlock here.
To me it looks like, that aio_poll could be called from iothread_run, even if
there are no outstanding request.
Opinions?
Christian