This RFC introduces per-thread constructors/destructors: * Per-thread constructors are functions called as the first thing from newly created threads. This can be used to initialize variables in thread-local storage, variables depending on the (tid_t) thread id, and to call setup functions that must be called from the thread itself. * Per-thread destructors are functions called (from the thread) as the last thing when a thread ends.
At this time, I am seeking feedback on the concept and the proposed limitations. Processes have __attribute__(constructor/destructor) to set up functions to be called before main(). Nothing similar exists for threads, so we have to design it ourselves. The proposed per-thread constructors/destructors should not apply to all threads - only to threads created through the DPDK threads API. Agree? DPDK has the RTE_INIT()/RTE_FINI() macros for adding process constructors/destructors at build time, so I propose a similar API, i.e. adding RTE_THREAD_INIT() and RTE_THREAD_FINI() macros to build a list of per-thread constructors and destructors at build time. Two functions that call the list of per-thread constructors respectively destructors will be introduced. The per-thread constructor function will be called from the newly created threads within DPDK: 1. EAL/SERVICE threads: In eal_thread_loop() before the loop. 2. CTRL threads: In ctrl_thread_init() before start_routine(). 3. Non-EAL threads: In rte_thread_register(). Are any thread types missing in the list above? The per-thread destructor function will also be registered by the per-thread constructor, using the POSIX pthread_cleanup_push() function. Examples of where per-thread constructors are useful: PRNG state initialization [1]: http://inbox.dpdk.org/dev/[email protected]/ PMU event setup [2]: http://inbox.dpdk.org/dev/[email protected]/T/#m3d29fbc301059f007425ac148a4113e66d2ef983 Please also refer to the discussion [3] about lcore init callbacks for further thoughts. Especially the de-facto inability to establish constructors/destructors at runtime. [3]: http://inbox.dpdk.org/dev/[email protected]/T/#m23b9a930a4050dc6b0305d3653754bd152c09ab7 Med venlig hilsen / Kind regards, -Morten Brørup
