Re: [Qemu-devel] race condition in qemu-kvm-1.0.1

[Marcelo Tosatti]

On Wed, Jun 27, 2012 at 12:35:22PM +0200, Peter Lieven wrote:
> Hi,
> 
> we recently came across multiple VMs racing and stopping working. It
> seems to happen when the system is at 100% cpu.
> One way to reproduce this is:
> qemu-kvm-1.0.1 with vnc-thread enabled
> 
> cmdline (or similar):
> /usr/bin/qemu-kvm-1.0.1 -net
> tap,vlan=141,script=no,downscript=no,ifname=tap15,vnet_hdr -net
> nic,vlan=141,model=virtio,macaddr=52:54:00:ff:00:f7 -drive 
> format=host_device,file=/dev/mapper/iqn.2001-05.com.equallogic:0-8a0906-efdf4e007-16700198c7f4fead-02-debug-race-hd01,if=virtio,cache=none,aio=native
> -m 2048 -smp 2,sockets=1,cores=2,threads=1 -monitor
> tcp:0:4026,server,nowait -vnc :26 -qmp tcp:0:3026,server,nowait
> -name 02-debug-race -boot order=dc,menu=off -cdrom
> /home/kvm/cdrom//root/ubuntu-12.04-server-amd64.iso -k de -pidfile
> /var/run/qemu/vm-221.pid -mem-prealloc -cpu
> host,+x2apic,model_id=Intel(R) Xeon(R) CPU           L5640  @
> 2.27GHz,-tsc -rtc base=utc -usb -usbdevice tablet -no-hpet -vga
> cirrus

Is it reproducible without vnc thread enabled?

> 
> it is important that the attached virtio image contains only zeroes.
> if the system boots from cd, select boot from first harddisk.
> the hypervisor then hangs at 100% cpu and neither monitor nor qmp
> are responsive anymore.
> 
> i have also seen customers reporting this when a VM is shut down.
> 
> if this is connected to the threaded vnc server it might be
> important to connected at this time.
> 
> debug backtrace attached.
> 
> Thanks,
> Peter
> 
> --
> 
> (gdb) file /usr/bin/qemu-kvm-1.0.1
> Reading symbols from /usr/bin/qemu-kvm-1.0.1...done.
> (gdb) attach 5145
> Attaching to program: /usr/bin/qemu-kvm-1.0.1, process 5145
> Reading symbols from /lib64/ld-linux-x86-64.so.2...(no debugging
> symbols found)...done.
> Loaded symbols for /lib64/ld-linux-x86-64.so.2
> [Thread debugging using libthread_db enabled]
> [New Thread 0x7f54d08b9700 (LWP 5253)]
> [New Thread 0x7f5552757700 (LWP 5152)]
> [New Thread 0x7f5552f58700 (LWP 5151)]
> 0x00007f5553c6b5a3 in select () from /lib/libc.so.6
> (gdb) info threads
>   4 Thread 0x7f5552f58700 (LWP 5151)  0x00007f5553c6a747 in ioctl ()
> from /lib/libc.so.6
>   3 Thread 0x7f5552757700 (LWP 5152)  0x00007f5553c6a747 in ioctl ()
> from /lib/libc.so.6
>   2 Thread 0x7f54d08b9700 (LWP 5253)  0x00007f5553f1a85c in
> pthread_cond_wait@@GLIBC_2.3.2 () from /lib/libpthread.so.0
> * 1 Thread 0x7f555550d700 (LWP 5145)  0x00007f5553c6b5a3 in select
> () from /lib/libc.so.6
> (gdb) thread apply all bt
> 
> Thread 4 (Thread 0x7f5552f58700 (LWP 5151)):
> #0  0x00007f5553c6a747 in ioctl () from /lib/libc.so.6
> #1  0x00007f5555727830 in kvm_vcpu_ioctl (env=0x7f5557652f10,
> type=44672) at /usr/src/qemu-kvm-1.0.1/kvm-all.c:1101
> #2  0x00007f555572728a in kvm_cpu_exec (env=0x7f5557652f10) at
> /usr/src/qemu-kvm-1.0.1/kvm-all.c:987
> #3  0x00007f55556f5c08 in qemu_kvm_cpu_thread_fn
> (arg=0x7f5557652f10) at /usr/src/qemu-kvm-1.0.1/cpus.c:740
> #4  0x00007f5553f159ca in start_thread () from /lib/libpthread.so.0
> #5  0x00007f5553c72cdd in clone () from /lib/libc.so.6
> #6  0x0000000000000000 in ?? ()
> 
> Thread 3 (Thread 0x7f5552757700 (LWP 5152)):
> #0  0x00007f5553c6a747 in ioctl () from /lib/libc.so.6
> #1  0x00007f5555727830 in kvm_vcpu_ioctl (env=0x7f555766ae60,
> type=44672) at /usr/src/qemu-kvm-1.0.1/kvm-all.c:1101
> #2  0x00007f555572728a in kvm_cpu_exec (env=0x7f555766ae60) at
> /usr/src/qemu-kvm-1.0.1/kvm-all.c:987
> #3  0x00007f55556f5c08 in qemu_kvm_cpu_thread_fn
> (arg=0x7f555766ae60) at /usr/src/qemu-kvm-1.0.1/cpus.c:740
> #4  0x00007f5553f159ca in start_thread () from /lib/libpthread.so.0
> #5  0x00007f5553c72cdd in clone () from /lib/libc.so.6
> #6  0x0000000000000000 in ?? ()
> 
> Thread 2 (Thread 0x7f54d08b9700 (LWP 5253)):
> #0  0x00007f5553f1a85c in pthread_cond_wait@@GLIBC_2.3.2 () from
> /lib/libpthread.so.0
> #1  0x00007f5555679f5d in qemu_cond_wait (cond=0x7f5557ede1e0,
> mutex=0x7f5557ede210) at qemu-thread-posix.c:113
> #2  0x00007f55556b06a1 in vnc_worker_thread_loop
> (queue=0x7f5557ede1e0) at ui/vnc-jobs-async.c:222
> #3  0x00007f55556b0b7f in vnc_worker_thread (arg=0x7f5557ede1e0) at
> ui/vnc-jobs-async.c:318
> #4  0x00007f5553f159ca in start_thread () from /lib/libpthread.so.0
> #5  0x00007f5553c72cdd in clone () from /lib/libc.so.6
> #6  0x0000000000000000 in ?? ()
> 
> Thread 1 (Thread 0x7f555550d700 (LWP 5145)):
> #0  0x00007f5553c6b5a3 in select () from /lib/libc.so.6
> #1  0x00007f55556516be in main_loop_wait (nonblocking=0) at main-loop.c:456
> #2  0x00007f5555647ad0 in main_loop () at /usr/src/qemu-kvm-1.0.1/vl.c:1482
> #3  0x00007f555564c698 in main (argc=38, argv=0x7ffff9d894a8,
> envp=0x7ffff9d895e0) at /usr/src/qemu-kvm-1.0.1/vl.c:3523
> (gdb) thread apply all bt full
> 
> Thread 4 (Thread 0x7f5552f58700 (LWP 5151)):
> #0  0x00007f5553c6a747 in ioctl () from /lib/libc.so.6
> No symbol table info available.
> #1  0x00007f5555727830 in kvm_vcpu_ioctl (env=0x7f5557652f10,
> type=44672) at /usr/src/qemu-kvm-1.0.1/kvm-all.c:1101
>         ret = 32597
>         arg = 0x0
>         ap = {{gp_offset = 24, fp_offset = 48, overflow_arg_area =
> 0x7f5552f57e50, reg_save_area = 0x7f5552f57d90}}
> #2  0x00007f555572728a in kvm_cpu_exec (env=0x7f5557652f10) at
> /usr/src/qemu-kvm-1.0.1/kvm-all.c:987
>         run = 0x7f55553e2000
>         ret = 0
>         run_ret = 0
> #3  0x00007f55556f5c08 in qemu_kvm_cpu_thread_fn
> (arg=0x7f5557652f10) at /usr/src/qemu-kvm-1.0.1/cpus.c:740
>         env = 0x7f5557652f10
>         r = 0
> #4  0x00007f5553f159ca in start_thread () from /lib/libpthread.so.0
> No symbol table info available.
> #5  0x00007f5553c72cdd in clone () from /lib/libc.so.6
> No symbol table info available.
> #6  0x0000000000000000 in ?? ()
> No symbol table info available.
> 
> Thread 3 (Thread 0x7f5552757700 (LWP 5152)):
> #0  0x00007f5553c6a747 in ioctl () from /lib/libc.so.6
> No symbol table info available.
> #1  0x00007f5555727830 in kvm_vcpu_ioctl (env=0x7f555766ae60,
> type=44672) at /usr/src/qemu-kvm-1.0.1/kvm-all.c:1101
>         ret = 0
>         arg = 0x0
>         ap = {{gp_offset = 24, fp_offset = 48, overflow_arg_area =
> 0x7f5552756e50, reg_save_area = 0x7f5552756d90}}
> #2  0x00007f555572728a in kvm_cpu_exec (env=0x7f555766ae60) at
> /usr/src/qemu-kvm-1.0.1/kvm-all.c:987
>         run = 0x7f55553df000
>         ret = 32597
>         run_ret = 1433358864
> #3  0x00007f55556f5c08 in qemu_kvm_cpu_thread_fn
> (arg=0x7f555766ae60) at /usr/src/qemu-kvm-1.0.1/cpus.c:740
>         env = 0x7f555766ae60
>         r = 65536
> #4  0x00007f5553f159ca in start_thread () from /lib/libpthread.so.0
> No symbol table info available.
> #5  0x00007f5553c72cdd in clone () from /lib/libc.so.6
> No symbol table info available.
> #6  0x0000000000000000 in ?? ()
> No symbol table info available.
> 
> Thread 2 (Thread 0x7f54d08b9700 (LWP 5253)):
> #0  0x00007f5553f1a85c in pthread_cond_wait@@GLIBC_2.3.2 () from
> /lib/libpthread.so.0
> ---Type <return> to continue, or q <return> to quit---
> No symbol table info available.
> #1  0x00007f5555679f5d in qemu_cond_wait (cond=0x7f5557ede1e0,
> mutex=0x7f5557ede210) at qemu-thread-posix.c:113
>         err = 32597
>         __func__ = "qemu_cond_wait"
> #2  0x00007f55556b06a1 in vnc_worker_thread_loop
> (queue=0x7f5557ede1e0) at ui/vnc-jobs-async.c:222
>         job = 0x7f5557edd510
>         entry = 0x0
>         tmp = 0x0
>         vs = {csock = -1, ds = 0x7f5557e8ec40, dirty = {{0, 0, 0}
> <repeats 2048 times>}, lossy_rect = 0x7f5557edd570, vd =
> 0x7f54d08ba010, need_update = 0, force_update = 0,
>           features = 227, absolute = 0, last_x = 0, last_y = 0,
> client_width = 0, client_height = 0, vnc_encoding = 6, major = 0,
> minor = 0, auth = 0,
>           challenge = '\000' <repeats 15 times>, info = 0x0, output
> = {capacity = 1230913, offset = 1448, buffer = 0x7f5558176d60 ""},
> input = {capacity = 0, offset = 0,
>             buffer = 0x0}, write_pixels = 0x7f55556b2aaf
> <vnc_write_pixels_generic>, clientds = {flags = 0 '\000', width =
> 640, height = 480, linesize = 1280,
>             data = 0x7f54d0c00000 "B\a", pf = {bits_per_pixel = 32 '
> ', bytes_per_pixel = 4 '\004', depth = 24 '\030', rmask = 16711680,
> gmask = 65280, bmask = 255, amask = 0,
>               rshift = 16 '\020', gshift = 8 '\b', bshift = 0
> '\000', ashift = 0 '\000', rmax = 255 '\377', gmax = 255 '\377',
> bmax = 255 '\377', amax = 0 '\000',
>               rbits = 8 '\b', gbits = 8 '\b', bbits = 8 '\b', abits
> = 0 '\000'}}, audio_cap = 0x0, as = {freq = 0, nchannels = 0, fmt =
> AUD_FMT_U8, endianness = 0},
>           read_handler = 0, read_handler_expect = 0, modifiers_state
> = '\000' <repeats 255 times>, led = 0x0, abort = false, output_mutex
> = {lock = {__data = {__lock = 0,
>                 __count = 0, __owner = 0, __nusers = 0, __kind = 0,
> __spins = 0, __list = {__prev = 0x0, __next = 0x0}}, __size = '\000'
> <repeats 39 times>, __align = 0}},
>           bh = 0x0, jobs_buffer = {capacity = 0, offset = 0, buffer
> = 0x0}, tight = {type = 0, quality = 255 '\377', compression = 9
> '\t', pixel24 = 0 '\000', tight = {
>               capacity = 0, offset = 0, buffer = 0x0}, tmp =
> {capacity = 0, offset = 0, buffer = 0x0}, zlib = {capacity = 0,
> offset = 0, buffer = 0x0}, gradient = {
>               capacity = 0, offset = 0, buffer = 0x0}, levels = {0,
> 0, 0, 0}, stream = {{next_in = 0x0, avail_in = 0, total_in = 0,
> next_out = 0x0, avail_out = 0,
>                 total_out = 0, msg = 0x0, state = 0x0, zalloc = 0,
> zfree = 0, opaque = 0x0, data_type = 0, adler = 0, reserved = 0},
> {next_in = 0x0, avail_in = 0, total_in = 0,
>                 next_out = 0x0, avail_out = 0, total_out = 0, msg =
> 0x0, state = 0x0, zalloc = 0, zfree = 0, opaque = 0x0, data_type =
> 0, adler = 0, reserved = 0}, {
>                 next_in = 0x0, avail_in = 0, total_in = 0, next_out
> = 0x0, avail_out = 0, total_out = 0, msg = 0x0, state = 0x0, zalloc
> = 0, zfree = 0, opaque = 0x0,
>                 data_type = 0, adler = 0, reserved = 0}, {next_in =
> 0x0, avail_in = 0, total_in = 0, next_out = 0x0, avail_out = 0,
> total_out = 0, msg = 0x0, state = 0x0,
>                 zalloc = 0, zfree = 0, opaque = 0x0, data_type = 0,
> adler = 0, reserved = 0}}}, zlib = {zlib = {capacity = 1229488,
> offset = 1152000,
>               buffer = 0x7f5557fe9320 ""}, tmp = {capacity =
> 1230913, offset = 20, buffer = 0x7f5558176d60 ""}, stream = {next_in
> = 0x7f5558102720 "\030\b ", avail_in = 0,
>               total_in = 7658880, next_out = 0x7f5558177308 "",
> avail_out = 1229465, total_out = 49027, msg = 0x0, state =
> 0x7f55581155e0,
>               zalloc = 0x7f55556a622f <vnc_zlib_zalloc>, zfree =
> 0x7f55556a626c <vnc_zlib_zfree>, opaque = 0x7f54d08a6810, data_type
> = 0, adler = 197164569, reserved = 0},
>             level = 9}, hextile = {send_tile = 0x7f55556a1180
> <send_hextile_tile_generic_32>}, zrle = {type = 0, fb = {capacity =
> 0, offset = 0, buffer = 0x0}, zrle = {
>               capacity = 0, offset = 0, buffer = 0x0}, tmp =
> {capacity = 0, offset = 0, buffer = 0x0}, zlib = {capacity = 0,
> offset = 0, buffer = 0x0}, stream = {next_in = 0x0,
>               avail_in = 0, total_in = 0, next_out = 0x0, avail_out
> = 0, total_out = 0, msg = 0x0, state = 0x0, zalloc = 0, zfree = 0,
> opaque = 0x0, data_type = 0, adler = 0,
>               reserved = 0}, palette = {pool = {{idx = 0, color = 0,
> next = {le_next = 0x0, le_prev = 0x0}} <repeats 256 times>}, size =
> 0, max = 0, bpp = 0, table = {{
>                   lh_first = 0x0} <repeats 256 times>}}}, zywrle =
> {buf = {0 <repeats 4096 times>}}, mouse_mode_notifier = {notify = 0,
> node = {tqe_next = 0x0,
>               tqe_prev = 0x0}}, next = {tqe_next = 0x0, tqe_prev = 0x0}}
>         n_rectangles = 1
>         saved_offset = 2
> #3  0x00007f55556b0b7f in vnc_worker_thread (arg=0x7f5557ede1e0) at
> ui/vnc-jobs-async.c:318
>         queue = 0x7f5557ede1e0
> #4  0x00007f5553f159ca in start_thread () from /lib/libpthread.so.0
> No symbol table info available.
> #5  0x00007f5553c72cdd in clone () from /lib/libc.so.6
> No symbol table info available.
> #6  0x0000000000000000 in ?? ()
> No symbol table info available.
> 
> ---Type <return> to continue, or q <return> to quit---
> Thread 1 (Thread 0x7f555550d700 (LWP 5145)):
> #0  0x00007f5553c6b5a3 in select () from /lib/libc.so.6
> No symbol table info available.
> #1  0x00007f55556516be in main_loop_wait (nonblocking=0) at main-loop.c:456
>         rfds = {fds_bits = {14197552, 0 <repeats 15 times>}}
>         wfds = {fds_bits = {0 <repeats 16 times>}}
>         xfds = {fds_bits = {0 <repeats 16 times>}}
>         ret = 32597
>         nfds = 23
>         tv = {tv_sec = 0, tv_usec = 817147}
>         timeout = 1000
> #2  0x00007f5555647ad0 in main_loop () at /usr/src/qemu-kvm-1.0.1/vl.c:1482
>         nonblocking = false
>         last_io = 1
> #3  0x00007f555564c698 in main (argc=38, argv=0x7ffff9d894a8,
> envp=0x7ffff9d895e0) at /usr/src/qemu-kvm-1.0.1/vl.c:3523
>         gdbstub_dev = 0x0
>         i = 64
>         snapshot = 0
>         linux_boot = 0
>         icount_option = 0x0
>         initrd_filename = 0x0
>         kernel_filename = 0x0
>         kernel_cmdline = 0x7f55557d8bef ""
>         boot_devices = "dc", '\000' <repeats 30 times>
>         ds = 0x7f5557e8ec40
>         dcl = 0x0
>         cyls = 0
>         heads = 0
>         secs = 0
>         translation = 0
>         hda_opts = 0x0
>         opts = 0x7f5557637cb0
>         olist = 0x7ffff9d89268
>         optind = 38
>         optarg = 0x7ffff9d89bed "cirrus"
>         loadvm = 0x0
>         machine = 0x7f5555b53500
>         cpu_model = 0x7ffff9d89b6f "host,+x2apic,model_id=Intel(R)
> Xeon(R) CPU", ' ' <repeats 11 times>, "L5640  @ 2.27GHz,-tsc"
>         pid_file = 0x7ffff9d89b43 "/var/run/qemu/vm-221.pid"
>         incoming = 0x0
>         show_vnc_port = 0
>         defconfig = 1
>         log_mask = 0x0
>         log_file = 0x0
>         mem_trace = {malloc = 0x7f5555649081 <malloc_and_trace>,
> realloc = 0x7f55556490b6 <realloc_and_trace>, free = 0x7f55556490fa
> <free_and_trace>, calloc = 0,
> ---Type <return> to continue, or q <return> to quit---
>           try_malloc = 0, try_realloc = 0}
>         trace_events = 0x0
>         trace_file = 0x0
> (gdb)
> 
> --
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