[Qemu-devel] Re: qemu-kvm segfaults in qemu_del_timer (0.10.5 and 0.10.6)

[Chris Webb]

Chris Webb <address@hidden> writes:

> With the following applied, VNC connections and disconnections still work
> correctly, so it doesn't horribly break anything, but I can't immediately
> confirm whether it will cure the rare segfaults as I haven't yet found a
> rapid way of reproducing the crashes other than by waiting for one.

Just to follow up on this: the backported patch has cured the vast majority of
VNC crashes we've been seeing on 0.10.6, although I've still seen this earlier
today:

Core was generated by `qemu-kvm -m 512 -smp 1 -uuid 
d6f2cb13-7421-4baa-a978-eda9bec9d075 -pidfile /var'.
Program terminated with signal 11, Segmentation fault.
[New process 16847]
[New process 16855]
(gdb) bt
#0  0x00007fe42e9c6cb1 in memcpy () from /lib/libc.so.6
#1  0x00000000004917e4 in vnc_write (vs=0x31a7f50, data=0x7fffe3a19230, len=2) 
at vnc.c:323
#2  0x00000000004919bf in vnc_write_u16 (vs=0x7fe2f8cae023, value=<value 
optimized out>) at vnc.c:1035
#3  0x0000000000491bf3 in vnc_framebuffer_update (vs=0x7fe2f8cae023, 
x=-475950544, y=2, w=16385, h=1, encoding=6)
    at vnc.c:286
#4  0x0000000000496660 in send_framebuffer_update (vs=0x7fe2f8cae023, 
x=-475950544, y=196, w=208, h=1) at vnc.c:598
#5  0x0000000000496f65 in vnc_update_client (opaque=<value optimized out>) at 
vnc.c:754
#6  0x000000000040822a in main_loop_wait (timeout=<value optimized out>)
    at /packages/qemu-kvm+vncfix/src-nUlCId/vl.c:1240
#7  0x000000000051753a in kvm_main_loop () at 
/packages/qemu-kvm+vncfix/src-nUlCId/qemu-kvm.c:596
#8  0x000000000040c8a5 in main (argc=<value optimized out>, argv=<value 
optimized out>, envp=<value optimized out>)
    at /packages/qemu-kvm+vncfix/src-nUlCId/vl.c:3850
(gdb) f 1
#1  0x00000000004917e4 in vnc_write (vs=0x31a7f50, data=0x7fffe3a19230, len=2) 
at vnc.c:323
323         memcpy(buffer->buffer + buffer->offset, data, len);
(gdb) f 1
#1  0x00000000004917e4 in vnc_write (vs=0x31a7f50, data=0x7fffe3a19230, len=2) 
at vnc.c:323
323         memcpy(buffer->buffer + buffer->offset, data, len);
(gdb) p *vs
$1 = {timer = 0x2b90b20, csock = 18, ds = 0x28a1a20, vd = 0x28b0fc0, 
need_update = 1, dirty_row = {{0, 0, 0, 
      0} <repeats 197 times>, {65535, 262128, 0, 0}, {4294967295, 1, 0, 0}, 
{4294967288, 262143, 0, 0}, {4294443008, 
      262143, 0, 0}, {131071, 262128, 0, 0}, {4294967295, 1, 0, 0}, 
{4294967292, 262143, 0, 0}, {4294443008, 262143, 
      0, 0}, {131071, 262136, 0, 0}, {4294967295, 1, 0, 0}, {4294967292, 
262143, 0, 0}, {4294443008, 262143, 0, 0}, {
      131071, 262136, 0, 0}, {4294967295, 1, 0, 0}, {4294967292, 262143, 0, 0}, 
{4294705152, 262143, 0, 0}, {131071, 
      262136, 0, 0}, {4294967295, 1, 0, 0}, {4294967294, 262143, 0, 0}, 
{4294705152, 262143, 0, 0}, {131071, 262140, 
      0, 0}, {4294967295, 1, 0, 0}, {4294967294, 262143, 0, 0}, {4294836224, 
262143, 0, 0}, {131071, 262140, 0, 0}, {
      4294967295, 1, 0, 0}, {4294967294, 262143, 0, 0}, {4294836224, 262143, 0, 
0}, {131071, 262140, 0, 0}, {
      4294967295, 1, 0, 0}, {4294967295, 262143, 0, 0}, {4294836224, 262143, 0, 
0}, {131071, 262142, 0, 0}, {
      4294967295, 1, 0, 0}, {4294967295, 262143, 0, 0}, {4294901760, 262143, 0, 
0}, {131071, 262142, 0, 0}, {
      4294967295, 1, 0, 0}, {4294967295, 262143, 0, 0}, {4294901760, 262143, 0, 
0}, {131071, 262142, 0, 0}, {
      4294967295, 131073, 0, 0}, {4294967295, 262143, 0, 0}, {4294901760, 
262143, 0, 0}, {131071, 262143, 0, 0}, {
      4294967295, 131073, 0, 0}, {4294967295, 262143, 0, 0}, {4294934528, 
262143, 0, 0}, {131071, 262143, 0, 0}, {
      4294967295, 131075, 0, 0}, {4294967295, 262143, 0, 0}, {4294934528, 
262143, 0, 0}, {131071, 262143, 0, 0}, {
      4294967295, 196611, 0, 0}, {4294967295, 262143, 0, 0}, {4294934528, 
262143, 0, 0}, {2147614719, 262143, 0, 0}, {
      4294967295, 196611, 0, 0}, {4294967295, 262143, 0, 0}, {4294950912, 
262143, 0, 0}, {2147614719, 262143, 0, 0}, {
      4294967295, 196611, 0, 0}, {4294967295, 262143, 0, 0}, {4294950912, 
262143, 0, 0}, {2147614719, 262143, 0, 0}, {
      4294967295, 229379, 0, 0}, {4294967295, 262143, 0, 0}, {4294950912, 
262143, 0, 0}, {3221356543, 262143, 0, 0}, {
      4294967295, 229379, 0, 0}, {4294967295, 262143, 0, 0}, {4294950912, 
262143, 0, 0}, {3221356543, 262143, 0, 0}, {
      4294967295, 229377, 0, 0}, {4294967295, 262143, 0, 0}, {4294959104, 
262143, 0, 0}, {3221356543, 262143, 0, 0}, {
      4294967295, 245761, 0, 0}, {4294967295, 262143, 0, 0}, {4294959104, 
262143, 0, 0}, {3758227455, 262143, 0, 0}, {
      4294967295, 245761, 0, 0}, {4294967295, 262143, 0, 0}, {4294959104, 
262143, 0, 0}, {3758227455, 262143, 0, 0}, {
      4294967295, 245761, 0, 0}, {4294967295, 262143, 0, 0}, {4294963200, 
262143, 0, 0}, {3758227455, 262143, 0, 0}, {
      4294967295, 253953, 0, 0}, {4294967295, 262143, 0, 0}, {4294963200, 
262143, 0, 0}, {4026662911, 262143, 0, 0}, {
      4294967295, 253953, 0, 0}, {4294967295, 262143, 0, 0}, {4294963200, 
262143, 0, 0}, {4026662911, 262143, 0, 0}, {
      4294967295, 253953, 0, 0}, {4294967295, 262143, 0, 0}, {4294965248, 
262143, 0, 0}, {4026662911, 262143, 0, 0}, {
      4294967295, 258049, 0, 0}, {4294967295, 262143, 0, 0}, {4294965248, 
262143, 0, 0}, {4026662911, 262143, 0, 0}, {
      4294967295, 258049, 0, 0}, {4294967295, 262143, 0, 0}, {4294965248, 
262143, 0, 0}, {4160815103, 262143, 0, 0}, {
      4294967295, 258049, 0, 0}, {4294967295, 262143, 0, 0}, {4294966272, 
262143, 0, 0}, {4160815103, 262143, 0, 0}, {
      4294967295, 258049, 0, 0}, {4294967295, 262143, 0, 0}, {4294966272, 
262143, 0, 0}, {4160815103, 262143, 0, 0}, {
      4294967295, 260097, 0, 0}, {4294967295, 262143, 0, 0}, {4294966272, 
262143, 0, 0}, {4227923967, 262143, 0, 0}, {
      4294967295, 260097, 0, 0}, {4294967295, 131071, 0, 0}, {4294966272, 
262143, 0, 0}, {4227923967, 262143, 0, 0}, {
      4294967295, 260097, 0, 0}, {4294967295, 131071, 0, 0}, {4294966784, 
262143, 0, 0}, {4227923967, 262143, 0, 0}, {
      4294967295, 261121, 0, 0}, {4294967295, 131071, 0, 0}, {4294966784, 
262143, 0, 0}, {4227923967, 262143, 0, 0}, {
      4294967295, 261120, 0, 0}, {4294967295, 131071, 0, 0}, {4294966784, 
262143, 0, 0}, {4261478399, 262143, 0, 0}, {
      4294967295, 261120, 0, 0}, {4294967295, 131071, 0, 0}, {4294967040, 
262143, 0, 0}, {4261478399, 262143, 0, 0}, {
      4294967295, 261120, 0, 0}, {4294967295, 131071, 0, 0}, {4294967040, 
262143, 0, 0}, {4261478399, 262143, 0, 0}, {
      4294967295, 261632, 0, 0}, {4294967295, 131071, 0, 0}, {4294967040, 
262143, 0, 0}, {4278222847, 262143, 0, 0}, {
      4294967295, 261632, 0, 0}, {4294967295, 131071, 0, 0}, {4294967040, 
262143, 0, 0}, {4278222847, 262143, 0, 0}, {
      4294967295, 261632, 0, 0}, {4294967295, 131071, 0, 0}, {4294967168, 
262143, 0, 0}, {4278222847, 262143, 0, 0}, {
      4294967295, 261888, 0, 0}, {4294967295, 131071, 0, 0}, {4294967168, 
262143, 0, 0}, {4278222847, 262143, 0, 0}, {
      4294967295, 261888, 0, 0}, {4294967295, 65535, 0, 0}, {4294967168, 
262143, 0, 0}, {4286611455, 262143, 0, 0}, {
      4294967295, 261888, 0, 0}, {4294967295, 65535, 0, 0}, {4294967232, 
262143, 0, 0}, {4286611455, 262143, 0, 0}, {
      4294967295, 261888, 0, 0}, {4294967295, 65535, 0, 0}, {4294967232, 
262143, 0, 0}, {4286611455, 262143, 0, 0}, {
      2147483647, 262016, 0, 0}, {4294967295, 65535, 0, 0}, {4294967232, 
262143, 0, 0}, {4286611455, 262143, 0, 0}, {
      2147483647, 262016, 0, 0}, {4294967295, 65535, 0, 0}, {4294967232, 
262143, 0, 0}, {4290805759, 262143, 0, 0}, {
      2147483647, 262016, 0, 0}, {4294967295, 65535, 0, 0}, {4294967264, 
262143, 0, 0}, {4290805759, 262143, 0, 0}, {
      2147483647, 262016, 0, 0}, {4294967295, 65535, 0, 0}, {4294967264, 
262143, 0, 0}, {4290789375, 262143, 0, 0}, {
      2147483647, 262080, 0, 0}...}, old_data = 0x2bbd1d0 "", features = 99, 
absolute = 1, last_x = -1, last_y = -1, 
  vnc_encoding = 6, tight_quality = 6 '\006', tight_compression = 9 '\t', major 
= 3, minor = 8, 
  challenge = "\314\351\243\267G\207\002\v\313\363\226\301ZQ\310m", output = 
{capacity = 2147485644, 
    offset = 18446744071562067987, 
    buffer = 0x7fe378cae010 
"H\247BE\311\251\237\305j\200|\344\372\331\232\001\302t`"}, input = {capacity = 
5120, 
    offset = 0, buffer = 0x31b0390 "\003\001"}, write_pixels = 0x491830 
<vnc_write_pixels_generic>, 
  send_hextile_tile = 0x492db0 <send_hextile_tile_generic_32>, clientds = 
{flags = 0 '\0', width = 800, height = 600, 
    linesize = 3200, data = 0x7fe40c2ad010 "", pf = {bits_per_pixel = 32 ' ', 
bytes_per_pixel = 4 '\004', 
      depth = 24 '\030', rmask = 0, gmask = 0, bmask = 0, amask = 0, rshift = 
16 '\020', gshift = 8 '\b', 
      bshift = 0 '\0', ashift = 24 '\030', rmax = 255 '\377', gmax = 255 
'\377', bmax = 255 '\377', 
      amax = 255 '\377', rbits = 8 '\b', gbits = 8 '\b', bbits = 8 '\b', abits 
= 8 '\b'}}, serverds = {
    flags = 2 '\002', width = 800, height = 600, linesize = 3200, data = 
0x7fe40c2ad010 "", 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 
'\0', ashift = 24 '\030', 
      rmax = 255 '\377', gmax = 255 '\377', bmax = 255 '\377', amax = 255 
'\377', rbits = 8 '\b', gbits = 8 '\b', 
      bbits = 8 '\b', abits = 8 '\b'}}, audio_cap = 0x0, as = {freq = 44100, 
nchannels = 2, fmt = AUD_FMT_S16, 
    endianness = 0}, read_handler = 0x495a10 <protocol_client_msg>, 
read_handler_expect = 1, 
  modifiers_state = '\0' <repeats 255 times>, zlib = {capacity = 1920304, 
offset = 2176, 
    buffer = 0x3680680 "A\271\237"}, zlib_tmp = {capacity = 2147485644, offset 
= 2147483353, 
    buffer = 0x7fe378cae010 
"H\247BE\311\251\237\305j\200|\344\372\331\232\001\302t`"}, zlib_stream = {{
      next_in = 0x3680f00 ":\244\215", avail_in = 0, total_in = 15141151424, 
next_out = 0x7fe3f8cae023 "", 
      avail_out = 1977, total_out = 2112923344, msg = 0x0, state = 0x31b2ed0, 
zalloc = 0x7fe42f528b90 <zcalloc>, 
      zfree = 0x7fe42f528b80 <zcfree>, opaque = 0x31a7f50, data_type = 0, adler 
= 1623013286, 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}}, next = 0x0}

Best wishes,

Chris.