Pandecode is not thread-safe (for a large number of reasons) and does not even
try to be. This is a problem when tracing (or just using PAN_MESA_DEBUG=sync)
multithreaded applications. The most common symptom of the problem are assertion
failures deep in the red-black tree implementation, which is not thread-safe.
Just protect the whole thing by a "in pandecode?" mutex, since this is not
performance sensitive code and we don't really care about the extra
serialization incurred. As pandecode does not recurse into itself, we may simply
lock at the beginning and unlock at the end of each entrypoint in pandecode,
which is thread-safe regardless of how pandecode is used. A few entrypoints are
refactored to avoid early returns to keep the lock/unlock calls in obvious
visual pairs.
Fixes flakes when running the CL CTS with PAN_MESA_DEBUG=sync like we would in
CI (e.g: events.event_flush)
Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Tested-by: Icecream95 <ixn@disroot.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17409>
Alyssa Rosenzweig
cc980ee0ed