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<p style="margin: 10px 0 0 0">It's been a while since I reviewed this, but the issue here was because of the way Apache subrequests work, and the fact that the locks aren't recursive.</p>
<p style="margin: 10px 0 0 0">shibd doesn't have a problem because it's threads don't recurse, but inside Apache you can get into a situation where the worker thread grabs the lock, then spawns a subrequest that tries to grab the same lock it's already holding. That's the deadlock, it's not a cross-thread issue.</p>
<p style="margin: 10px 0 0 0">By moving the write lock out of the worker threads, they can always recursively grab the read lock and any waiting on the write lock will end once the refresh thread finishes its work and releases it.</p>
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