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9e467af804
Since threads were introduced in 1.8, the USE_PRIVATE_CACHE mode of the shctx was not updated to use locks. Originally it was meant to disable sharing between processes, so it removes the lock/unlock instructions. But with threads enabled, it's not possible to work like this anymore. It's easy to see that once built with private cache and threads enabled, sending violent SSL traffic to the the process instantly makes it die. The HTTP cache is very likely affected as well. This patch addresses this by falling back to our native spinlocks when USE_PRIVATE_CACHE is used. In practice we could use them also for other modes and remove all older implementations, but this patch aims at keeping the changes very low and easy to backport. A new SHCTX_LOCK label was added to help with debugging, but OTHER_LOCK might be usable as well for backports. An even lighter approach for backports may consist in always declaring the lock (or reusing "waiters"), and calling pl_take_s() for the lock() and pl_drop_s() for the unlock() operation. This could even be used in all modes (process and threads), even when thread support is disabled. Subsequent patches will further clean up this area. This patch must be backported to all supported versions since 1.8.