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b2f38c13d1
A few loops waiting for threads to synchronize such as thread_isolate() rightfully filter the thread masks via the threads_enabled field that contains the list of enabled threads. However, it doesn't use an atomic load on it. Before 2.7, the equivalent variables were marked as volatile and were always reloaded. In 2.7 they're fields in ha_tgroup_ctx[], and the risk that the compiler keeps them in a register inside a loop is not null at all. In practice when ha_thread_relax() calls sched_yield() or an x86 PAUSE instruction, it could be verified that the variable is always reloaded. If these are avoided (e.g. architecture providing neither solution), it's visible in asm code that the variables are not reloaded. In this case, if a thread exists just between the moment the two values are read, the loop could spin forever. This patch adds the required _HA_ATOMIC_LOAD() on the relevant threads_enabled fields. It must be backported to 2.7.
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)