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Hello<br>
I have been experimenting with my custom app that uses webkit2gtk.
<br>
For testing I use Ubuntu 14.04.1 LTS linux.<br>
While testing I have encountered one strange thing.<br>
<br>
Usually when WebKitWebProcess crashes or or is killed for some
reason, then "web-process-crashed" signal is emitted in UI process.
WebProcess is respawned and everything works fine after that.<br>
<br>
But rarely when WebProcess is being re-spawned, process locks
somewhere, leaving web session unresponsive.<br>
<br>
The only solution (without restarting the whole app) is to kill only
WebProcess, which will cause UI process to re spawn WebProcess
again. <br>
After this and reloading the page everything works fine again.<br>
<br>
I have investigated problem further and I have discovered that
locked WebProcess is running with only one system thread.<br>
This was unusual for WebKitWebProcess which usulay runs with several
threads.<br>
<br>
After attaching debuger to such process I suspect for the problem to
have something to do with "dbus_launch".<br>
<br>
Here I got one of such processes on gdb. The stack trace looks like
this:
<div class="highlighted-data dark">
<div class="highlight">
<pre><code class=" hljs groovy"><span id="LC1" class="line">(gdb) bt</span>
<span id="LC2" class="line">#<span class="hljs-number">0</span> __lll_lock_wait () at ..<span class="hljs-regexp">/nptl/</span>sysdeps<span class="hljs-regexp">/unix/</span>sysv<span class="hljs-regexp">/linux/</span>x86_64/lowlevellock.<span class="hljs-string">S:</span><span class="hljs-number">135</span></span>
<span id="LC3" class="line">#<span class="hljs-number">1</span> <span class="hljs-number">0x00007fda3cfa4657</span> <span class="hljs-keyword">in</span> _L_lock_909 () from <span class="hljs-regexp">/lib/</span>x86_64-linux-gnu/libpthread.so<span class="hljs-number">.0</span></span>
<span id="LC4" class="line">#<span class="hljs-number">2</span> <span class="hljs-number">0x00007fda3cfa4480</span> <span class="hljs-keyword">in</span> __GI___pthread_mutex_lock (mutex=<span class="hljs-number">0x7fd9e4f7d420</span>) at ..<span class="hljs-regexp">/nptl/</span>pthread_mutex_lock.<span class="hljs-string">c:</span><span class="hljs-number">79</span></span>
<span id="LC5" class="line">#<span class="hljs-number">3</span> <span class="hljs-number">0x00007fd9e4d54e23</span> <span class="hljs-keyword">in</span> ?? () from /usr/lib/x86_64-linux-gnu/libp11-kit.so.0</span>
<span id="LC6" class="line">#4 0x00007fda3d279f87 in __libc_fork () at ../nptl/sysdeps/unix/sysv/linux/x86_64/../fork.c:<span class="hljs-number">188</span></span>
<span id="LC7" class="line">#<span class="hljs-number">5</span> <span class="hljs-number">0x00007fda37cfe54c</span> <span class="hljs-keyword">in</span> fork_exec_with_pipes (intermediate_child=intermediate_child<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0</span>, working_directory=working_directory<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x0</span>, </span>
<span id="LC8" class="line"> argv=<span class="hljs-number">0x7fd9d0003e60</span>, envp=envp<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x0</span>, close_descriptors=close_descriptors<span class="hljs-annotation">@entry</span>=<span class="hljs-number">1</span>, search_path=search_path<span class="hljs-annotation">@entry</span>=<span class="hljs-number">1</span>, </span>
<span id="LC9" class="line"> search_path_from_envp=search_path_from_envp<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0</span>, stdout_to_null=stdout_to_null<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0</span>, stderr_to_null=<span class="hljs-number">0</span>, </span>
<span id="LC10" class="line"> child_inherits_stdin=child_inherits_stdin<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0</span>, file_and_argv_zero=file_and_argv_zero<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0</span>, cloexec_pipes=cloexec_pipes<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0</span>, </span>
<span id="LC11" class="line"> child_setup=child_setup<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x0</span>, user_data=user_data<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x0</span>, child_pid=child_pid<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf7e8</span>, standard_input=standard_input<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x0</span>, </span>
<span id="LC12" class="line"> standard_output=standard_output<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf7e0</span>, standard_error=standard_error<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf7e4</span>, error=error<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf988</span>)</span>
<span id="LC13" class="line"> at <span class="hljs-regexp">/build/</span>buildd<span class="hljs-regexp">/glib2.0-2.40.2/</span>.<span class="hljs-regexp">/glib/</span>gspawn.<span class="hljs-string">c:</span><span class="hljs-number">1326</span></span>
<span id="LC14" class="line">#<span class="hljs-number">6</span> <span class="hljs-number">0x00007fda37cfee18</span> <span class="hljs-keyword">in</span> g_spawn_sync (working_directory=working_directory<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x0</span>, argv=<optimized out>, envp=envp<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x0</span>, </span>
<span id="LC15" class="line"> flags=flags<span class="hljs-annotation">@entry</span>=G_SPAWN_SEARCH_PATH, child_setup=child_setup<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x0</span>, user_data=user_data<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x0</span>, </span>
<span id="LC16" class="line"> standard_output=standard_output<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf920</span>, standard_error=standard_error<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf928</span>, exit_status=exit_status<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf91c</span>, </span>
<span id="LC17" class="line"> error=error<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf988</span>) at <span class="hljs-regexp">/build/</span>buildd<span class="hljs-regexp">/glib2.0-2.40.2/</span>.<span class="hljs-regexp">/glib/</span>gspawn.<span class="hljs-string">c:</span><span class="hljs-number">277</span></span>
<span id="LC18" class="line">#<span class="hljs-number">7</span> <span class="hljs-number">0x00007fda37cff517</span> <span class="hljs-keyword">in</span> g_spawn_command_line_sync (</span>
<span id="LC19" class="line"> command_line=command_line<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9d0003d40</span> <span class="hljs-string">"dbus-launch --autolaunch=b0e3226568f3ba144a55c2e2548aba21 --binary-syntax --close-stderr"</span>, </span>
<span id="LC20" class="line"> standard_output=standard_output<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf920</span>, standard_error=standard_error<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf928</span>, exit_status=exit_status<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf91c</span>, </span>
<span id="LC21" class="line"> error=error<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf988</span>) at <span class="hljs-regexp">/build/</span>buildd<span class="hljs-regexp">/glib2.0-2.40.2/</span>.<span class="hljs-regexp">/glib/</span>gspawn.<span class="hljs-string">c:</span><span class="hljs-number">721</span></span>
<span id="LC22" class="line">#<span class="hljs-number">8</span> <span class="hljs-number">0x00007fda3911bc00</span> <span class="hljs-keyword">in</span> get_session_address_dbus_launch (error=error<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf988</span>) at <span class="hljs-regexp">/build/</span>buildd<span class="hljs-regexp">/glib2.0-2.40.2/</span>.<span class="hljs-regexp">/gio/</span>gdbusaddress.<span class="hljs-string">c:</span><span class="hljs-number">1073</span></span>
<span id="LC23" class="line">#<span class="hljs-number">9</span> <span class="hljs-number">0x00007fda3911d48a</span> <span class="hljs-keyword">in</span> get_session_address_platform_specific (error=<span class="hljs-number">0x7fd9e5fbf988</span>) at <span class="hljs-regexp">/build/</span>buildd<span class="hljs-regexp">/glib2.0-2.40.2/</span>.<span class="hljs-regexp">/gio/</span>gdbusaddress.<span class="hljs-string">c:</span><span class="hljs-number">1446</span></span>
<span id="LC24" class="line">#<span class="hljs-number">10</span> g_dbus_address_get_for_bus_sync (bus_type=bus_type<span class="hljs-annotation">@entry</span>=G_BUS_TYPE_SESSION, cancellable=cancellable<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x0</span>, error=error<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbfa78</span>)</span>
<span id="LC25" class="line"> at <span class="hljs-regexp">/build/</span>buildd<span class="hljs-regexp">/glib2.0-2.40.2/</span>.<span class="hljs-regexp">/gio/</span>gdbusaddress.<span class="hljs-string">c:</span><span class="hljs-number">1530</span></span>
<span id="LC26" class="line">#<span class="hljs-number">11</span> <span class="hljs-number">0x00007fda391281fe</span> <span class="hljs-keyword">in</span> get_uninitialized_connection (bus_type=G_BUS_TYPE_SESSION, cancellable=cancellable<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x0</span>, error=error<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbfa78</span>)</span>
<span id="LC27" class="line"> at <span class="hljs-regexp">/build/</span>buildd<span class="hljs-regexp">/glib2.0-2.40.2/</span>.<span class="hljs-regexp">/gio/</span>gdbusconnection.<span class="hljs-string">c:</span><span class="hljs-number">6965</span></span>
<span id="LC28" class="line">#<span class="hljs-number">12</span> <span class="hljs-number">0x00007fda3912d6bb</span> <span class="hljs-keyword">in</span> g_bus_get_sync (bus_type=<optimized out>, cancellable=<span class="hljs-number">0x0</span>, error=<span class="hljs-number">0x7fd9e5fbfa78</span>)</span>
<span id="LC29" class="line"> at <span class="hljs-regexp">/build/</span>buildd<span class="hljs-regexp">/glib2.0-2.40.2/</span>.<span class="hljs-regexp">/gio/</span>gdbusconnection.<span class="hljs-string">c:</span><span class="hljs-number">7042</span></span>
<span id="LC30" class="line">#<span class="hljs-number">13</span> <span class="hljs-number">0x00007fd9ec18cf90</span> <span class="hljs-keyword">in</span> ?? () from /usr/lib/x86_64-linux-gnu/gio/modules/libdconfsettings.so</span>
<span id="LC31" class="line">#14 0x00007fd9ec18d06d in ?? () from /usr/lib/x86_64-linux-gnu/gio/modules/libdconfsettings.so</span>
<span id="LC32" class="line">#15 0x00007fda37cbace5 in g_main_dispatch (context=0x1cbcce0) at /build/buildd/glib2.0-2.40.2/./glib/gmain.c:<span class="hljs-number">3064</span></span>
<span id="LC33" class="line">#<span class="hljs-number">16</span> g_main_context_dispatch (context=context<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x1cbcce0</span>) at <span class="hljs-regexp">/build/</span>buildd<span class="hljs-regexp">/glib2.0-2.40.2/</span>.<span class="hljs-regexp">/glib/</span>gmain.<span class="hljs-string">c:</span><span class="hljs-number">3663</span></span>
<span id="LC34" class="line">#<span class="hljs-number">17</span> <span class="hljs-number">0x00007fda37cbb048</span> <span class="hljs-keyword">in</span> g_main_context_iterate (context=context<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x1cbcce0</span>, block=block<span class="hljs-annotation">@entry</span>=<span class="hljs-number">1</span>, dispatch=dispatch<span class="hljs-annotation">@entry</span>=<span class="hljs-number">1</span>, self=<optimized out>)</span>
<span id="LC35" class="line"> at <span class="hljs-regexp">/build/</span>buildd<span class="hljs-regexp">/glib2.0-2.40.2/</span>.<span class="hljs-regexp">/glib/</span>gmain.<span class="hljs-string">c:</span><span class="hljs-number">3734</span></span>
<span id="LC36" class="line">#<span class="hljs-number">18</span> <span class="hljs-number">0x00007fda37cbb0ec</span> <span class="hljs-keyword">in</span> g_main_context_iteration (context=<span class="hljs-number">0x1cbcce0</span>, may_block=<span class="hljs-number">1</span>) at <span class="hljs-regexp">/build/</span>buildd<span class="hljs-regexp">/glib2.0-2.40.2/</span>.<span class="hljs-regexp">/glib/</span>gmain.<span class="hljs-string">c:</span><span class="hljs-number">3795</span></span>
<span id="LC37" class="line">#<span class="hljs-number">19</span> <span class="hljs-number">0x00007fd9ec18d1ad</span> <span class="hljs-keyword">in</span> ?? () from /usr/lib/x86_64-linux-gnu/gio/modules/libdconfsettings.so</span>
<span id="LC38" class="line">#20 0x00007fda37cdff05 in g_thread_proxy (data=0x1c71cf0) at /build/buildd/glib2.0-2.40.2/./glib/gthread.c:<span class="hljs-number">764</span></span>
<span id="LC39" class="line">#<span class="hljs-number">21</span> <span class="hljs-number">0x00007fda3cfa2182</span> <span class="hljs-keyword">in</span> start_thread (arg=<span class="hljs-number">0x7fd9e5fc0700</span>) at pthread_create.<span class="hljs-string">c:</span><span class="hljs-number">312</span></span>
<span id="LC40" class="line">#<span class="hljs-number">22</span> <span class="hljs-number">0x00007fda3d2b330d</span> <span class="hljs-keyword">in</span> clone () at ..<span class="hljs-regexp">/sysdeps/</span>unix<span class="hljs-regexp">/sysv/</span>linux<span class="hljs-regexp">/x86_64/</span>clone.<span class="hljs-string">S:</span><span class="hljs-number">111</span></span>
<span id="LC41" class="line"></span></code></pre>
</div>
</div>
<p>It seems everything hangs in frame 7: when spawning a
dbus-launch:</p>
<div class="highlighted-data dark">
<div class="highlight">
<pre><code class=" hljs groovy"><span id="LC1" class="line">(gdb) f <span class="hljs-number">7</span></span>
<span id="LC2" class="line">#<span class="hljs-number">7</span> <span class="hljs-number">0x00007fda37cff517</span> <span class="hljs-keyword">in</span> g_spawn_command_line_sync (</span>
<span id="LC3" class="line"> command_line=command_line<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9d0003d40</span> <span class="hljs-string">"dbus-launch --autolaunch=b0e3226568f3ba144a55c2e2548aba21 --binary-syntax --close-stderr"</span>, </span>
<span id="LC4" class="line"> standard_output=standard_output<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf920</span>, standard_error=standard_error<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf928</span>, exit_status=exit_status<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf91c</span>, </span>
<span id="LC5" class="line"> error=error<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf988</span>) at <span class="hljs-regexp">/build/</span>buildd<span class="hljs-regexp">/glib2.0-2.40.2/</span>.<span class="hljs-regexp">/glib/</span>gspawn.<span class="hljs-string">c:</span><span class="hljs-number">721</span></span>
<span id="LC6" class="line"><span class="hljs-number">721</span> <span class="hljs-keyword">in</span> <span class="hljs-regexp">/build/</span>buildd<span class="hljs-regexp">/glib2.0-2.40.2/</span>.<span class="hljs-regexp">/glib/</span>gspawn.c</span>
<span id="LC7" class="line"></span>
<span id="LC8" class="line"></span></code></pre>
</div>
</div>
<p>And a little later in frame 5:</p>
<div class="highlighted-data dark">
<div class="highlight">
<pre><code class=" hljs nix"><span id="LC1" class="line"><span class="hljs-comment">#5 0x00007fda37cfe54c in fork_exec_with_pipes (intermediate_child=intermediate_child@entry=0, working_directory=working_directory@entry=0x0, </span></span>
<span id="LC2" class="line"> <span class="hljs-variable">argv=</span><span class="hljs-number">0</span>x7fd9d0003e60, <span class="hljs-variable">envp=</span>envp@<span class="hljs-variable">entry=</span><span class="hljs-number">0</span>x0, <span class="hljs-variable">close_descriptors=</span>close_descriptors@<span class="hljs-variable">entry=</span><span class="hljs-number">1</span>, <span class="hljs-variable">search_path=</span>search_path@<span class="hljs-variable">entry=</span><span class="hljs-number">1</span>, </span>
<span id="LC3" class="line"> <span class="hljs-variable">search_path_from_envp=</span>search_path_from_envp@<span class="hljs-variable">entry=</span><span class="hljs-number">0</span>, <span class="hljs-variable">stdout_to_null=</span>stdout_to_null@<span class="hljs-variable">entry=</span><span class="hljs-number">0</span>, <span class="hljs-variable">stderr_to_null=</span><span class="hljs-number">0</span>, </span>
<span id="LC4" class="line"> <span class="hljs-variable">child_inherits_stdin=</span>child_inherits_stdin@<span class="hljs-variable">entry=</span><span class="hljs-number">0</span>, <span class="hljs-variable">file_and_argv_zero=</span>file_and_argv_zero@<span class="hljs-variable">entry=</span><span class="hljs-number">0</span>, <span class="hljs-variable">cloexec_pipes=</span>cloexec_pipes@<span class="hljs-variable">entry=</span><span class="hljs-number">0</span>, </span>
<span id="LC5" class="line"> <span class="hljs-variable">child_setup=</span>child_setup@<span class="hljs-variable">entry=</span><span class="hljs-number">0</span>x0, <span class="hljs-variable">user_data=</span>user_data@<span class="hljs-variable">entry=</span><span class="hljs-number">0</span>x0, <span class="hljs-variable">child_pid=</span>child_pid@<span class="hljs-variable">entry=</span><span class="hljs-number">0</span>x7fd9e5fbf7e8, <span class="hljs-variable">standard_input=</span>standard_input@<span class="hljs-variable">entry=</span><span class="hljs-number">0</span>x0, </span>
<span id="LC6" class="line"> <span class="hljs-variable">standard_output=</span>standard_output@<span class="hljs-variable">entry=</span><span class="hljs-number">0</span>x7fd9e5fbf7e0, <span class="hljs-variable">standard_error=</span>standard_error@<span class="hljs-variable">entry=</span><span class="hljs-number">0</span>x7fd9e5fbf7e4, <span class="hljs-variable">error=</span>error@<span class="hljs-variable">entry=</span><span class="hljs-number">0</span>x7fd9e5fbf988)</span>
<span id="LC7" class="line"> at /build/buildd/glib2.<span class="hljs-number">0</span>-<span class="hljs-number">2.40</span>.<span class="hljs-number">2</span>/./glib/gspawn.c:<span class="hljs-number">1326</span></span>
<span id="LC8" class="line"><span class="hljs-number">1326</span> <span class="hljs-keyword">in</span> /build/buildd/glib2.<span class="hljs-number">0</span>-<span class="hljs-number">2.40</span>.<span class="hljs-number">2</span>/./glib/gspawn.c</span>
<span id="LC9" class="line">(gdb) i locals</span>
<span id="LC10" class="line"><span class="hljs-variable">pid =</span> -<span class="hljs-number">1</span></span>
<span id="LC11" class="line"><span class="hljs-variable">stdin_pipe =</span> {-<span class="hljs-number">1</span>, -<span class="hljs-number">1</span>}</span>
<span id="LC12" class="line"><span class="hljs-variable">stdout_pipe =</span> {<span class="hljs-number">18</span>, <span class="hljs-number">19</span>}</span>
<span id="LC13" class="line"><span class="hljs-variable">stderr_pipe =</span> {<span class="hljs-number">20</span>, <span class="hljs-number">21</span>}</span>
<span id="LC14" class="line"><span class="hljs-variable">child_err_report_pipe =</span> {<span class="hljs-number">14</span>, <span class="hljs-number">17</span>}</span>
<span id="LC15" class="line"><span class="hljs-variable">child_pid_report_pipe =</span> {-<span class="hljs-number">1</span>, -<span class="hljs-number">1</span>}</span>
<span id="LC16" class="line"><span class="hljs-variable">pipe_flags =</span> <span class="hljs-number">0</span></span>
<span id="LC17" class="line"><span class="hljs-variable">status =</span> <span class="hljs-number">4</span></span>
<span id="LC18" class="line"></span>
<span id="LC19" class="line"></span></code></pre>
</div>
</div>
<p>And frame 8:</p>
<pre><code class=" hljs groovy"><span id="LC1" class="line">(gdb) f <span class="hljs-number">8</span></span>
<span id="LC2" class="line">#<span class="hljs-number">8</span> <span class="hljs-number">0x00007fda3911bc00</span> <span class="hljs-keyword">in</span> get_session_address_dbus_launch (error=error<span class="hljs-annotation">@entry</span>=<span class="hljs-number">0x7fd9e5fbf988</span>) at <span class="hljs-regexp">/build/</span>buildd<span class="hljs-regexp">/glib2.0-2.40.2/</span>.<span class="hljs-regexp">/gio/</span>gdbusaddress.<span class="hljs-string">c:</span><span class="hljs-number">1073</span></span>
<span id="LC3" class="line"><span class="hljs-number">1073</span> <span class="hljs-regexp">/build/</span>buildd<span class="hljs-regexp">/glib2.0-2.40.2/</span>.<span class="hljs-regexp">/gio/</span>gdbusaddress.<span class="hljs-string">c:</span> No such file or directory.</span>
<span id="LC4" class="line">(gdb) i locals</span>
<span id="LC5" class="line">ret = <span class="hljs-number">0x0</span></span>
<span id="LC6" class="line">machine_id = <span class="hljs-number">0x7fd9d0003d10</span> <span class="hljs-string">"b0e3226568f3ba144a55c2e2548aba21"</span></span>
<span id="LC7" class="line">command_line = <span class="hljs-number">0x7fd9d0003d40</span> <span class="hljs-string">"dbus-launch --autolaunch=b0e3226568f3ba144a55c2e2548aba21 --binary-syntax --close-stderr"</span></span>
<span id="LC8" class="line">launch_stdout = <span class="hljs-number">0x0</span></span>
<span id="LC9" class="line">launch_stderr = <span class="hljs-number">0x0</span></span>
<span id="LC10" class="line">exit_status = <span class="hljs-number">32729</span></span>
<span id="LC11" class="line">old_dbus_verbose = <span class="hljs-number">0x0</span></span>
<span id="LC12" class="line">restore_dbus_verbose = <span class="hljs-number">0
Best
Miha
</span></span></code></pre>
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