The old code assumed that the thread that created a request buffer for a given signal-emitting thread would be the latter thread, and thus a thread-local pointer to the request buffer could be used. This turns out not to be true: the GUI thread tends to be responsible for constructing the request buffers for pre-registered threads. That mechanism has been replaced by using a RWLock protected map using pthread_t as the key and the request buffer as the value. This allows any thread to create and register the request buffers used between any other pair of threads (because the lookup always uses a pthread_t). The symptoms of this problem were a signal emitted in an audioengine thread that was propagated to the target thread, but when the target thread scans its request buffers for requests, it finds nothing (because it didn't know about the request buffer). In a sense, the signal was successfully delivered to the target thread, but no meaningful work (i.e the signal handler) is performed.
245 lines
8.2 KiB
C++
245 lines
8.2 KiB
C++
/*
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* Copyright (C) 2009-2018 Paul Davis <paul@linuxaudiosystems.com>
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* Copyright (C) 2010 Carl Hetherington <carl@carlh.net>
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* Copyright (C) 2015-2017 Robin Gareus <robin@gareus.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <cstring>
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#include <pthread.h>
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#include "pbd/compose.h"
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#include "pbd/debug.h"
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#include "pbd/event_loop.h"
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#include "pbd/error.h"
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#include "pbd/pthread_utils.h"
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#include "pbd/i18n.h"
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using namespace PBD;
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using namespace std;
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static void do_not_delete_the_loop_pointer (void*) { }
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Glib::Threads::Private<EventLoop> EventLoop::thread_event_loop (do_not_delete_the_loop_pointer);
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Glib::Threads::RWLock EventLoop::thread_buffer_requests_lock;
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EventLoop::ThreadRequestBufferList EventLoop::thread_buffer_requests;
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EventLoop::RequestBufferSuppliers EventLoop::request_buffer_suppliers;
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EventLoop::EventLoop (string const& name)
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: _name (name)
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{
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}
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EventLoop::~EventLoop ()
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{
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trash.sort();
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trash.unique();
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for (std::list<InvalidationRecord*>::iterator r = trash.begin(); r != trash.end(); ++r) {
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if (!(*r)->in_use ()) {
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delete *r;
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}
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}
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trash.clear ();
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}
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EventLoop*
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EventLoop::get_event_loop_for_thread()
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{
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return thread_event_loop.get ();
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}
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void
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EventLoop::set_event_loop_for_thread (EventLoop* loop)
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{
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thread_event_loop.set (loop);
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}
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void*
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EventLoop::invalidate_request (void* data)
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{
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InvalidationRecord* ir = (InvalidationRecord*) data;
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/* Some of the requests queued with an EventLoop may involve functors
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* that make method calls to objects whose lifetime is shorter
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* than the EventLoop's. We do not want to make those calls if the
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* object involve has been destroyed. To prevent this, we
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* provide a way to invalidate those requests when the object is
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* destroyed.
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*
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* An object was passed to __invalidator() which added a callback to
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* EventLoop::invalidate_request() to its "notify when destroyed"
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* list. __invalidator() returned an InvalidationRecord that has been
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* to passed to this function as data.
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*
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* The object is currently being destroyed and so we want to
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* mark all requests involving this object that are queued with
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* any EventLoop as invalid.
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*
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* As of April 2012, we are usign sigc::trackable as the base object
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* used to queue calls to ::invalidate_request() to be made upon
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* destruction, via its ::add_destroy_notify_callback() API. This is
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* not necessarily ideal, but it is very close to precisely what we
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* want, and many of the objects we want to do this with already
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* inherit (indirectly) from sigc::trackable.
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*/
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if (ir->event_loop) {
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DEBUG_TRACE (PBD::DEBUG::EventLoop, string_compose ("%1: invalidating request from %2 (%3) @ %4\n", pthread_name(), ir->event_loop, ir->event_loop->event_loop_name(), ir));
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Glib::Threads::RWLock::WriterLock lm (ir->event_loop->slot_invalidation_rwlock());
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ir->invalidate ();
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ir->event_loop->trash.push_back(ir);
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}
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return 0;
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}
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vector<EventLoop::ThreadBufferMapping>
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EventLoop::get_request_buffers_for_target_thread (const std::string& target_thread)
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{
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vector<ThreadBufferMapping> ret;
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Glib::Threads::RWLock::WriterLock lm (thread_buffer_requests_lock);
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for (ThreadRequestBufferList::const_iterator x = thread_buffer_requests.begin();
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x != thread_buffer_requests.end(); ++x) {
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if (x->second.target_thread_name == target_thread) {
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ret.push_back (x->second);
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}
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}
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DEBUG_TRACE (PBD::DEBUG::EventLoop, string_compose ("for thread \"%1\", found %2 request buffers\n", target_thread, ret.size()));
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return ret;
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}
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void
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EventLoop::register_request_buffer_factory (const string& target_thread_name,
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void* (*factory)(uint32_t))
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{
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RequestBufferSupplier trs;
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trs.name = target_thread_name;
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trs.factory = factory;
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{
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Glib::Threads::RWLock::WriterLock lm (thread_buffer_requests_lock);
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request_buffer_suppliers.push_back (trs);
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}
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}
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void
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EventLoop::pre_register (const string& emitting_thread_name, uint32_t num_requests)
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{
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/* Threads that need to emit signals "towards" other threads, but with
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RT safe behavior may be created before the receiving threads
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exist. This makes it impossible for them to use the
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ThreadCreatedWithRequestSize signal to notify receiving threads of
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their existence.
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This function creates a request buffer for them to use with
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the (not yet) created threads, and stores it where the receiving
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thread can find it later.
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*/
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ThreadBufferMapping mapping;
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Glib::Threads::RWLock::WriterLock lm (thread_buffer_requests_lock);
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for (RequestBufferSuppliers::iterator trs = request_buffer_suppliers.begin(); trs != request_buffer_suppliers.end(); ++trs) {
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if (!trs->factory) {
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/* no factory - no request buffer required or expected */
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continue;
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}
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if (emitting_thread_name == trs->name) {
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/* no need to register an emitter with itself */
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continue;
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}
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mapping.emitting_thread = pthread_self();
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mapping.target_thread_name = trs->name;
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/* Allocate a suitably sized request buffer. This will set the
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* thread-local variable that holds a pointer to this request
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* buffer.
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*/
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mapping.request_buffer = trs->factory (num_requests);
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/* now store it where the receiving thread (trs->name) can find
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it if and when it is created. (Discovery happens in the
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AbstractUI constructor. Note that if
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*/
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const string key = string_compose ("%1/%2", emitting_thread_name, mapping.target_thread_name);
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/* management of the thread_request_buffers map works as
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* follows:
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*
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* when the factory method was called above, the pointer to the
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* created buffer is set as a thread-local-storage (TLS) value
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* for this (the emitting) thread.
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*
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* The TLS value is set up with a destructor that marks the
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* request buffer as "dead" when the emitting thread exits.
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*
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* An entry will remain in the map after the thread exits.
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*
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* The receiving thread may (if it receives requests from other
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* threads) notice the dead buffer. If it does, it will delete
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* the request buffer, and call
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* ::remove_request_buffer_from_map() to get rid of it from the map.
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*
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* This does mean that the lifetime of the request buffer is
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* indeterminate: if the receiving thread were to receive no
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* further requests, the request buffer will live on
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* forever. But this is OK, because if there are no requests
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* arriving, the receiving thread is not attempting to use the
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* request buffer(s) in any way.
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*
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* Note, however, that *if* an emitting thread is recreated
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* with the same name (e.g. when a control surface is
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* enabled/disabled/enabled), then the request buffer for the
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* new thread will replace the map entry for the key, because
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* of the matching thread names. This does mean that
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* potentially the request buffer can leak in this case, but
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* (a) these buffers are not really that large anyway (b) the
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* scenario is not particularly common (c) the buffers would
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* typically last across a session instance if not program
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* lifetime anyway.
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*/
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thread_buffer_requests[key] = mapping;
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DEBUG_TRACE (PBD::DEBUG::EventLoop, string_compose ("pre-registered request buffer for \"%1\" to send to \"%2\", buffer @ %3 (key was %4)\n",
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emitting_thread_name, trs->name, mapping.request_buffer, key));
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}
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}
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void
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EventLoop::remove_request_buffer_from_map (void* ptr)
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{
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Glib::Threads::RWLock::WriterLock lm (thread_buffer_requests_lock);
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for (ThreadRequestBufferList::iterator x = thread_buffer_requests.begin(); x != thread_buffer_requests.end(); ++x) {
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if (x->second.request_buffer == ptr) {
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thread_buffer_requests.erase (x);
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break;
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}
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}
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}
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