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2018-03-21Implementation of true asynchronous signaling between processesRickard Green
Communication between Erlang processes has conceptually always been performed through asynchronous signaling. The runtime system implementation has however previously preformed most operation synchronously. In a system with only one true thread of execution, this is not problematic (often the opposite). In a system with multiple threads of execution (as current runtime system implementation with SMP support) it becomes problematic. This since it often involves locking of structures when updating them which in turn cause resource contention. Utilizing true asynchronous communication often avoids these resource contention issues. The case that triggered this change was contention on the link lock due to frequent updates of the monitor trees during communication with a frequently used server. The signal order delivery guarantees of the language makes it hard to change the implementation of only some signals to use true asynchronous signaling. Therefore the implementations of (almost) all signals have been changed. Currently the following signals have been implemented as true asynchronous signals: - Message signals - Exit signals - Monitor signals - Demonitor signals - Monitor triggered signals (DOWN, CHANGE, etc) - Link signals - Unlink signals - Group leader signals All of the above already defined as asynchronous signals in the language. The implementation of messages signals was quite asynchronous to begin with, but had quite strict delivery constraints due to the ordering guarantees of signals between a pair of processes. The previously used message queue partitioned into two halves has been replaced by a more general signal queue partitioned into three parts that service all kinds of signals. More details regarding the signal queue can be found in comments in the erl_proc_sig_queue.h file. The monitor and link implementations have also been completely replaced in order to fit the new asynchronous signaling implementation as good as possible. More details regarding the new monitor and link implementations can be found in the erl_monitor_link.h file.
2017-07-17erts: Replace usage of all erts_smp prefixes to just ertsLukas Larsson
2017-07-17erts: Remove ERTS_SMP and USE_THREAD definesLukas Larsson
This refactor was done using the unifdef tool like this: for file in $(find erts/ -name *.[ch]); do unifdef -t -f defile -o $file $file; done where defile contained: #define ERTS_SMP 1 #define USE_THREADS 1 #define DDLL_SMP 1 #define ERTS_HAVE_SMP_EMU 1 #define SMP 1 #define ERL_BITS_REENTRANT 1 #define ERTS_USE_ASYNC_READY_Q 1 #define FDBLOCK 1 #undef ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT #define ERTS_POLL_ASYNC_INTERRUPT_SUPPORT 0 #define ERTS_POLL_USE_WAKEUP_PIPE 1 #define ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE 1 #undef ERTS_HAVE_PLAIN_EMU #undef ERTS_SIGNAL_STATE
2016-06-10erts: Fix undefined shift to msb in erl_processBjörn-Egil Dahlberg
2016-04-15erts: Implement tracer modulesLukas Larsson
Add the possibility to use modules as trace data receivers. The functions in the module have to be nifs as otherwise complex trace probes will be very hard to handle (complex means trace probes for ports for example). This commit changes the way that the ptab->tracer field works from always being an immediate, to now be NIL if no tracer is present or else be the tuple {TracerModule, TracerState} where TracerModule is an atom that is later used to lookup the appropriate tracer callbacks to call and TracerState is just passed to the tracer callback. The default process and port tracers have been rewritten to use the new API. This commit also changes the order which trace messages are delivered to the potential tracer process. Any enif_send done in a tracer module may be delayed indefinitely because of lock order issues. If a message is delayed any other trace message send from that process is also delayed so that order is preserved for each traced entity. This means that for some trace events (i.e. send/receive) the events may come in an unintuitive order (receive before send) to the trace receiver. Timestamps are taken when the trace message is generated so trace messages from differented processes may arrive with the timestamp out of order. Both the erlang:trace and seq_trace:set_system_tracer accept the new tracer module tracers and also the backwards compatible arguments. OTP-10267
2016-03-15update copyright-yearHenrik Nord
2015-06-18Change license text to APLv2Bruce Yinhe
2015-05-08Optimized timer implementationRickard Green
2014-12-10Use the new 64-bit atomic ops APIRickard Green
2013-08-07erts: Fix race in ptab that can cause PID mix-upsSverker Eriksson
Since: R16B01 Symptom: A spawned process may get the same PID as an existing process. The new process will "steal" the PID and make the old process unreachable through the PID. The problem also applies to port identities but has only been seen for processes. Conditions: SMP emulator with at least two scheduler threads. Rapid spawning and termination of a large number of processes. A small number of free slots in the process table will also increase the risk for this bug. Workaround: Use command line options "+P legacy" and "+Q legacy" Cause: The race happens if a process terminates and gets stalled while releasing its process table slot. The stall has to be so long (due to OS preemptive scheduling most probably) for other schedluer threads to consume all other free slots for newly spawn processes. Fix: Write invalid-markers in the free-pid-table and do atomic exhange operations in retry-loops to make sure each thread gets a unique PID.
2013-06-12Update copyright yearsBjörn-Egil Dahlberg
2013-05-17Introduce a better id allocation algorithm for PTabsRickard Green
2013-04-03Be less eager requesting wakeup for cleanup jobsRickard Green
2012-12-03Improve configuration of process and port tablesRickard Green
2012-12-03Use ptab functionality also for portsRickard Green
2012-12-03Prepare for use of ptab functionality also for portsRickard Green
2012-12-03Generalize process table implementationRickard Green