Description:
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serialize() seems to be not thread safe. Scripts crash with SIGSEGV or SIGABORT on a regular basis if parallel threads do serialization with pthreads. Sometimes this happens at the end of the script on shutdown and sometimes in the middle of script execution. As it is a race condition there is no deterministic way to reproduce it but the attached script fails after some time in almost all cases.

Test script:
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https://gist.github.com/brstgt/e04d08c237d84003103050dc7c371acd

Serialized file required as "entities.txt" in test script: https://cl.ly/2v3Y1o2S351Q

Run in loop until it segfaults or aborts. Normally between 1-30s

while true; do php scripts/segv.php || break; done



Expected result:
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No SIGABORT or SIGSEGV

Actual result:
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https://gist.github.com/brstgt/76e3e1135872e2ae1770ae4e59b66696