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The thread dump mechanism that is used by "show threads" and by the panic dump is overly complicated due to an initial misdesign. It firsts wakes all threads, then serializes their dumps, then releases them, while taking extreme care not to face colliding dumps. In fact this is not what we need and it reached a limit where big machines cannot dump all their threads anymore due to buffer size limitations. What is needed instead is to be able to dump *one* thread, and to let the requester iterate on all threads. That's what this patch does. It adds the thread_dump_buffer to the struct thread_ctx so that the requester offers the buffer to the thread that is about to be dumped. This buffer also serves as a lock. A thread at rest has a NULL, a valid pointer indicates the thread is using it, and 0x1 (NULL+1) is used by the dumped thread to tell the requester it's done. This makes sure that a given thread is dumped once at a time. In addition to this, the calling thread decides whether it accesses the thread by itself or via the debug signal handler, in order to get a backtrace. This is much saner because the calling thread is free to do whatever it wants with the buffer after each thread is dumped, and there is no dependency between threads, once they've dumped, they're free to continue (and possibly to dump for another requester if needed). Finally, when the THREAD_DUMP feature is disabled and the debug signal is not used, the requester accesses the thread by itself like before. For now we still have the buffer size limitation but it will be addressed in future patches.
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)