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Given that a "count" value of 32M was seen in _shctx_wait4lock(), it is very important to prevent this from happening again. It's absolutely essential to prevent the value from growing unbounded because with an increase of the number of threads, the number of successive failed attempts will necessarily grow. Instead now we're scanning all 2^p-1 values from 3 to 255 and are bounding to count to 255 so that in the worst case each thread tries an xchg every 255 failed read attempts. That's one every 4 on average per thread when there are 64 threads, which corresponds to the initial count of 4 for the first attempt so it seems like a reasonable value to keep a low latency. The bug was introduced with the shctx entries in 1.5 so the fix must be backported to all versions. Before 1.8 the function was called _shared_context_wait4lock() and was in shctx.c.
The HAProxy documentation has been split into a number of different files for ease of use. Please refer to the following files depending on what you're looking for : - INSTALL for instructions on how to build and install HAProxy - BRANCHES to understand the project's life cycle and what version to use - LICENSE for the project's license - CONTRIBUTING for the process to follow to submit contributions The more detailed documentation is located into the doc/ directory : - doc/intro.txt for a quick introduction on HAProxy - doc/configuration.txt for the configuration's reference manual - doc/lua.txt for the Lua's reference manual - doc/SPOE.txt for how to use the SPOE engine - doc/network-namespaces.txt for how to use network namespaces under Linux - doc/management.txt for the management guide - doc/regression-testing.txt for how to use the regression testing suite - doc/peers.txt for the peers protocol reference - doc/coding-style.txt for how to adopt HAProxy's coding style - doc/internals for developer-specific documentation (not all up to date)