A note about mod_shib2 and mod_http2

[Jacob Lundberg]

Hi Scott et al.,

We have been testing HTTP/2 on our SP again.  I've attempted to backport
the CPPXT-116 patches to apply them to Debian's 1.6.3-1~bpo9 (patch
attached).  However, we are still seeing pairs of xmltooling calls
deadlock.  Strangely enough, now it happens before there are any shibd
configuration changes.  F.e.:

Thread 195 (Thread 0x7f98a3dc1700 (LWP 4980)):
#0  0x00007f99153d0508 in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0
#1  0x00007f990fed5513 in xmltooling::CondWaitImpl::timedwait(xmltooling::Mutex*, int) () from /usr/lib/x86_64-linux-gnu/libxmltooling-lite.so.7
#2  0x00007f99109b34db in ?? () from /usr/lib/x86_64-linux-gnu/libshibsp-lite.so.7
#3  0x00007f99153ca494 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#4  0x00007f991510baff in clone () from /lib/x86_64-linux-gnu/libc.so.6

Thread 194 (Thread 0x7f98a45c2700 (LWP 4966)):
#0  0x00007f99153d015f in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0
#1  0x00007f990fecab53 in xmltooling::ReloadableXMLFile::reload_fn(void*) () from /usr/lib/x86_64-linux-gnu/libxmltooling-lite.so.7
#2  0x00007f99153ca494 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#3  0x00007f991510baff in clone () from /lib/x86_64-linux-gnu/libc.so.6

This does not appear to block SP activity any more, so I wonder if it
just blocks the first request and subsequent requests are fine.
However, it does completely occupy a pair of CPU cores.

Do you think my backported patch is flawed?  If you are interested in
additional information or I should comment on the ticket, just let me
know.

Thanks,
-Jacob

-- 

Jacob Lundberg
AVP, IT Architecture
503.290.0100 (voice)
503.973.5252 (fax)
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