Susan Hinrichs created TS-3970:
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Summary: Core in PluginVC
Key: TS-3970
URL: https://issues.apache.org/jira/browse/TS-3970
Project: Traffic Server
Issue Type: Bug
Reporter: Susan Hinrichs
One of our plugins moving from 5.0.1 to 5.3.x (plus 6.0 backports) started
seeing the following stack trace with high frequency.
{code}
Program terminated with signal 11, Segmentation fault.
#0 0x000000000054c232 in PluginVC::process_read_side (this=0x2b9ace2f3850,
other_side_call=true) at PluginVC.cc:638
in PluginVC.cc
#0 0x000000000054c232 in PluginVC::process_read_side (this=0x2b9ace2f3850,
other_side_call=true) at PluginVC.cc:638
#1 0x000000000054be2a in PluginVC::process_write_side (this=0x2b9ace2f3a40,
other_side_call=false) at PluginVC.cc:555
#2 0x000000000054acdb in PluginVC::main_handler (this=0x2b9ace2f3a40, event=1,
data=0x2b9b1e32e930) at PluginVC.cc:208
#3 0x0000000000510c84 in Continuation::handleEvent (this=0x2b9ace2f3a40,
event=1, data=0x2b9b1e32e930) at ../iocore/eventsystem/I_Continuation.h:145
#4 0x000000000079a2a6 in EThread::process_event (this=0x2b9ab63d9010,
e=0x2b9b1e32e930, calling_code=1) at UnixEThread.cc:128
#5 0x000000000079a474 in EThread::execute (this=0x2b9ab63d9010) at
UnixEThread.cc:179
#6 0x0000000000799851 in spawn_thread_internal (a=0x2fea360) at Thread.cc:85
#7 0x00002b9ab457e9d1 in start_thread () from /lib64/libpthread.so.0
#8 0x00000030d38e88fd in clone () from /lib64/libc.so.6
{code}
The output buffer fetched by PluginVC::process_read_side was NULL.
I think they reason this appears in 5.3 is due to the fix for TS-3522. Before
that change only one do_io_read was made very early to set up the read from
server. This bug fix delays the real read to later and pulls mbuf out of
server_buffer_reader. In some cases for this plugin, the mbuf is NULL by the
time we get there.
I fixed the core by using server_session->read_buffer in the do_io_read instead
of server_buffer_reader->mbuf. This seems to fix the problem.
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