<html><body><div style="font-family: arial, helvetica, sans-serif; font-size: 12pt; color: #000000"><div>OK (re-adding lttng-dev)<br></div><div><br></div><span id="zwchr" data-marker="__DIVIDER__">----- On Jul 17, 2015, at 9:09 AM, Dilong Zheng <Dilong.Zheng@mitel.com> wrote:<br></span><div data-marker="__QUOTED_TEXT__"><blockquote style="border-left:2px solid #1010FF;margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><style style="display:none;"><!-- P {margin-top:0;margin-bottom:0;} --></style>
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I was using lttng-ust 2.5.4 but now I'm moving up to lttng-ust 2.5.5 (which should be the latest 2.5 version)
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<div>Thanks,</div>
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<div>Dilong<br>
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<div id="divRplyFwdMsg" dir="ltr"><span style="font-size: 11pt; color: #000000; font-family: Calibri,sans-serif;" data-mce-style="font-size: 11pt; color: #000000; font-family: Calibri,sans-serif;" face="Calibri, sans-serif" color="#000000"><b>From:</b> Mathieu Desnoyers <mathieu.desnoyers@efficios.com><br>
<b>Sent:</b> Thursday, July 16, 2015 12:00 AM<br>
<b>To:</b> Dilong Zheng<br>
<b>Cc:</b> lttng-dev<br>
<b>Subject:</b> Re: [lttng-dev] SIGSEGV __event_probe, C++ application (static linking)</span>
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<div><span id="zwchr">----- On Jul 13, 2015, at 4:37 PM, Dilong Zheng <Dilong.Zheng@mitel.com> wrote:<br>
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<p>Hi,</p>
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<p>I have instrumented a C++ application with user space tracepoints. When I run the application and do a: "lttng list -u" command, I am able to see all my available tracepoints for the application. However when I enable those user space tracepoints and then
start the trace, a core gets dumped and examining the core file in gdb I see the following error:</p>
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<p><span style="font-size:10pt; color:rgb(255,0,0)"><span style="font-family:"Courier New",monospace; color:rgb(255,0,0)"><span style="color:rgb(255,0,0)">Program terminated with signal SIGSEGV, Segmentation fault.</span></span><br style="font-family:"Courier New",monospace; color:rgb(255,0,0)">
<span style="font-family:"Courier New",monospace; color:rgb(255,0,0)"><span style="color:rgb(255,0,0)">#0 0x00000000 in ?? ()</span></span></span></p>
<p>...</p>
<p><span style="font-family:"Courier New",monospace; font-size:10pt">(gdb) bt</span><br style="font-family:"Courier New",monospace; font-size:10pt">
<span style="font-family:"Courier New",monospace; font-size:10pt; color:rgb(255,0,0)"><span style="color:rgb(255,0,0)">#0 0x00000000 in ?? ()</span></span><br style="font-family:"Courier New",monospace; font-size:10pt; color:rgb(255,0,0)">
<span style="font-family:"Courier New",monospace; font-size:10pt; color:rgb(255,0,0)"><span style="color:rgb(255,0,0)">#1 0x08dd1088 in __event_probe__mike___sem_wait_entry (__tp_data=0xef92d818)</span></span><br style="font-family:"Courier New",monospace; font-size:10pt; color:rgb(255,0,0)">
<span style="font-family:"Courier New",monospace; font-size:10pt; color:rgb(255,0,0)"><span style="color:rgb(255,0,0)"> at /localhome/zhengd/override_mcd/System/SS_Inc/./sem_wrapper.h:67</span></span><br style="font-family:"Courier New",monospace; font-size:10pt; color:rgb(255,0,0)">
<span style="font-family:"Courier New",monospace; font-size:10pt; color:rgb(255,0,0)"><span style="color:rgb(255,0,0)">#2 0x08dd44d9 in __tracepoint_cb_mike___sem_wait_entry () at /localhome/zhengd/override_mc /System/SS_Inc/sem_wrapper.h:67</span></span><br style="font-family:"Courier New",monospace; font-size:10pt; color:rgb(255,0,0)">
<span style="font-family:"Courier New",monospace; font-size:10pt; color:rgb(255,0,0)"><span style="color:rgb(255,0,0)">#3 __wrap_sem_wait (sem=0xf43014c8) at /localhome/zhengd/override_mcd/System/System_Services/SysServices_Linux/SystemLinux.cpp:1877</span></span></p>
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<p><b>Contextual Information:</b> I would like to trace all calls to <span style="font-size:10pt; font-family:"Courier New",monospace">
<span style="font-family:"Courier New",monospace">sem_wait()</span></span> in my application. I am simply using a wrapper sem_wait function where I can place
<span style="font-family:"Courier New",monospace; font-size:10pt">tracepoint()</span> calls. Here's what the sem_wait wrapper looks like:</p>
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<p><span style="font-size:10pt; font-family:"Courier New",monospace"><span style="font-family:"Courier New",monospace">extern "C" int __real_sem_wait(sem_t*);</span></span></p>
<p><span style="font-size:10pt; font-family:"Courier New",monospace"><span style="font-family:"Courier New",monospace">extern "C" int __wrap_sem_wait(sem_t* sem) </span></span></p>
<p><span style="font-size:10pt; font-family:"Courier New",monospace"><span style="font-family:"Courier New",monospace">{</span></span></p>
<p><span style="font-size:10pt; font-family:"Courier New",monospace"><span style="font-family:"Courier New",monospace"> tracepoint(mike, sem_wait_entry); </span></span></p>
<p><span style="font-size:10pt; font-family:"Courier New",monospace"><span style="font-family:"Courier New",monospace"> int ret = __real_sem_wait(sem);</span></span></p>
<p><span style="font-size:10pt; font-family:"Courier New",monospace"><span style="font-family:"Courier New",monospace"> tracepoint(mike, sem_wait_exit, ret);</span></span></p>
<p><span style="font-size:10pt; font-family:"Courier New",monospace"><br style="font-family:"Courier New",monospace">
</span></p>
<p><span style="font-size:10pt; font-family:"Courier New",monospace"><span style="font-family:"Courier New",monospace"> return ret; </span></span></p>
<p><span style="font-size:10pt; font-family:"Courier New",monospace"><span style="font-family:"Courier New",monospace">}</span></span></p>
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<p>Here is the TRACEPOINT_EVENT macro found in my tracepoint provider header file (which was generated using lttng-gen-tp command line utility):</p>
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<p><span style="font-family:"Courier New",monospace; font-size:10pt">TRACEPOINT_EVENT(mike,
</span></p>
<p><span style="font-family:"Courier New",monospace; font-size:10pt"> sem_wait_entry,</span></p>
<p><span style="font-family:"Courier New",monospace; font-size:10pt"> TP_ARGS(),</span></p>
<p><span style="font-family:"Courier New",monospace; font-size:10pt"> TP_FIELDS()</span></p>
<p><span style="font-family:"Courier New",monospace; font-size:10pt">)</span><br>
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<p>And I am statically linking by using an existing CPP file (file with the __wrap_sem_wait() function) to create probes. I would just like to know any possible reasons why this error may be happening given the above mentioned circumstances and what I may be
able to try in order to fix this.</p>
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<div>Which UST version do you use ? Make sure you upgrade to latest,<br>
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<div>since we have fixed a similar segfault issue with probes compiled in<br>
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<div>C++ not so long ago.<br>
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<div>Thanks,<br>
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<div>Mathieu<br>
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<p>Thanks,</p>
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<p>Dilong <br>
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<div>-- <br>
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<div>Mathieu Desnoyers<br>
EfficiOS Inc.<br>
http://www.efficios.com</div>
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</div><br></blockquote></div><br><div data-marker="__SIG_POST__">-- <br></div><div>Mathieu Desnoyers<br>EfficiOS Inc.<br>http://www.efficios.com</div></div></body></html>