395 lines
14 KiB
C++
395 lines
14 KiB
C++
/*
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Copyright (C) 2012 Paul Davis
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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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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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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <unistd.h>
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#include <iostream>
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#include "pbd/stacktrace.h"
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#include "pbd/abstract_ui.h"
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#include "pbd/pthread_utils.h"
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#include "pbd/failed_constructor.h"
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#include "pbd/debug.h"
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#include "i18n.h"
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using namespace std;
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template<typename RequestBuffer> void
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cleanup_request_buffer (void* ptr)
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{
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RequestBuffer* rb = (RequestBuffer*) ptr;
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/* there is the question of why we don't simply erase the request
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* buffer and delete it right here, since we have to take the lock
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* anyway.
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*
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* as of april 24th 2012, i don't have a good answer to that.
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*/
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{
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Glib::Threads::Mutex::Lock lm (rb->ui.request_buffer_map_lock);
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rb->dead = true;
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}
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}
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template<typename R>
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Glib::Threads::Private<typename AbstractUI<R>::RequestBuffer> AbstractUI<R>::per_thread_request_buffer (cleanup_request_buffer<AbstractUI<R>::RequestBuffer>);
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template <typename RequestObject>
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AbstractUI<RequestObject>::AbstractUI (const string& name)
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: BaseUI (name)
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{
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void (AbstractUI<RequestObject>::*pmf)(string,pthread_t,string,uint32_t) = &AbstractUI<RequestObject>::register_thread;
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/* better to make this connect a handler that runs in the UI event loop but the syntax seems hard, and
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register_thread() is thread safe anyway.
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*/
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PBD::ThreadCreatedWithRequestSize.connect_same_thread (new_thread_connection, boost::bind (pmf, this, _1, _2, _3, _4));
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}
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template <typename RequestObject> void
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AbstractUI<RequestObject>::register_thread (string target_gui, pthread_t thread_id, string /*thread name*/, uint32_t num_requests)
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{
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/* the calling thread wants to register with the thread that runs this
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* UI's event loop, so that it will have its own per-thread queue of
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* requests. this means that when it makes a request to this UI it can
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* do so in a realtime-safe manner (no locks).
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*/
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if (target_gui != name()) {
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/* this UI is not the UI that the calling thread is trying to
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register with
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*/
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return;
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}
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/* the per_thread_request_buffer is a thread-private variable.
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See pthreads documentation for more on these, but the key
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thing is that it is a variable that as unique value for
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each thread, guaranteed.
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*/
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RequestBuffer* b = per_thread_request_buffer.get();
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if (b) {
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/* thread already registered with this UI
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*/
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return;
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}
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/* create a new request queue/ringbuffer */
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b = new RequestBuffer (num_requests, *this);
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{
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/* add the new request queue (ringbuffer) to our map
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so that we can iterate over it when the time is right.
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This step is not RT-safe, but is assumed to be called
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only at thread initialization time, not repeatedly,
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and so this is of little consequence.
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*/
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Glib::Threads::Mutex::Lock lm (request_buffer_map_lock);
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request_buffers[thread_id] = b;
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}
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/* set this thread's per_thread_request_buffer to this new
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queue/ringbuffer. remember that only this thread will
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get this queue when it calls per_thread_request_buffer.get()
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the second argument is a function that will be called
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when the thread exits, and ensures that the buffer is marked
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dead. it will then be deleted during a call to handle_ui_requests()
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*/
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per_thread_request_buffer.set (b);
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}
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template <typename RequestObject> RequestObject*
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AbstractUI<RequestObject>::get_request (RequestType rt)
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{
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RequestBuffer* rbuf = per_thread_request_buffer.get ();
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RequestBufferVector vec;
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/* see comments in ::register_thread() above for an explanation of
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the per_thread_request_buffer variable
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*/
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if (rbuf != 0) {
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/* the calling thread has registered with this UI and therefore
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* we have a per-thread request queue/ringbuffer. use it. this
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* "allocation" of a request is RT-safe.
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*/
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rbuf->get_write_vector (&vec);
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if (vec.len[0] == 0) {
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DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1: no space in per thread pool for request of type %2\n", name(), rt));
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return 0;
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}
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DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1: allocated per-thread request of type %2, caller %3\n", name(), rt, pthread_name()));
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vec.buf[0]->type = rt;
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vec.buf[0]->valid = true;
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return vec.buf[0];
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}
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/* calling thread has not registered, so just allocate a new request on
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* the heap. the lack of registration implies that realtime constraints
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* are not at work.
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*/
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DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1: allocated normal heap request of type %2, caller %3\n", name(), rt, pthread_name()));
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RequestObject* req = new RequestObject;
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req->type = rt;
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return req;
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}
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template <typename RequestObject> void
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AbstractUI<RequestObject>::handle_ui_requests ()
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{
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RequestBufferMapIterator i;
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RequestBufferVector vec;
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/* check all registered per-thread buffers first */
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request_buffer_map_lock.lock ();
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for (i = request_buffers.begin(); i != request_buffers.end(); ++i) {
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while (true) {
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/* we must process requests 1 by 1 because
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the request may run a recursive main
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event loop that will itself call
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handle_ui_requests. when we return
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from the request handler, we cannot
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expect that the state of queued requests
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is even remotely consistent with
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the condition before we called it.
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*/
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i->second->get_read_vector (&vec);
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if (vec.len[0] == 0) {
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break;
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} else {
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if (vec.buf[0]->valid) {
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request_buffer_map_lock.unlock ();
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do_request (vec.buf[0]);
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request_buffer_map_lock.lock ();
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if (vec.buf[0]->invalidation) {
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vec.buf[0]->invalidation->requests.remove (vec.buf[0]);
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}
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i->second->increment_read_ptr (1);
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}
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}
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}
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}
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/* clean up any dead request buffers (their thread has exited) */
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for (i = request_buffers.begin(); i != request_buffers.end(); ) {
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if ((*i).second->dead) {
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DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1/%2 deleting dead per-thread request buffer for %3 @ %4\n",
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name(), pthread_name(), i->second));
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delete (*i).second;
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RequestBufferMapIterator tmp = i;
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++tmp;
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request_buffers.erase (i);
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i = tmp;
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} else {
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++i;
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}
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}
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request_buffer_map_lock.unlock ();
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/* and now, the generic request buffer. same rules as above apply */
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Glib::Threads::Mutex::Lock lm (request_list_lock);
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while (!request_list.empty()) {
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RequestObject* req = request_list.front ();
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request_list.pop_front ();
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/* We need to use this lock, because its the one
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returned by slot_invalidation_mutex() and protects
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against request invalidation.
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*/
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request_buffer_map_lock.lock ();
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if (!req->valid) {
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DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1/%2 handling invalid heap request, type %3, deleting\n", name(), pthread_name(), req->type));
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delete req;
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request_buffer_map_lock.unlock ();
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continue;
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}
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/* we're about to execute this request, so its
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too late for any invalidation. mark
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the request as "done" before we start.
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*/
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if (req->invalidation) {
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DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1/%2 remove request from its invalidation list\n", name(), pthread_name()));
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/* after this call, if the object referenced by the
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* invalidation record is deleted, it will no longer
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* try to mark the request as invalid.
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*/
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req->invalidation->requests.remove (req);
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}
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/* at this point, an object involved in a functor could be
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* deleted before we actually execute the functor. so there is
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* a race condition that makes the invalidation architecture
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* somewhat pointless.
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*
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* really, we should only allow functors containing shared_ptr
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* references to objects to enter into the request queue.
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*/
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request_buffer_map_lock.unlock ();
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/* unlock the request lock while we execute the request, so
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* that we don't needlessly block other threads (note: not RT
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* threads since they have their own queue) from making requests.
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*/
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lm.release ();
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DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1/%2 execute request type %3\n", name(), pthread_name(), req->type));
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/* and lets do it ... this is a virtual call so that each
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* specific type of UI can have its own set of requests without
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* some kind of central request type registration logic
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*/
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do_request (req);
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DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1/%2 delete heap request type %3\n", name(), pthread_name(), req->type));
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delete req;
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/* re-acquire the list lock so that we check again */
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lm.acquire();
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}
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}
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template <typename RequestObject> void
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AbstractUI<RequestObject>::send_request (RequestObject *req)
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{
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/* This is called to ask a given UI to carry out a request. It may be
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* called from the same thread that runs the UI's event loop (see the
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* caller_is_self() case below), or from any other thread.
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*/
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if (base_instance() == 0) {
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return; /* XXX is this the right thing to do ? */
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}
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if (caller_is_self ()) {
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/* the thread that runs this UI's event loop is sending itself
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a request: we dispatch it immediately and inline.
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*/
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DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1/%2 direct dispatch of request type %3\n", name(), pthread_name(), req->type));
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do_request (req);
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} else {
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/* If called from a different thread, we first check to see if
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* the calling thread is registered with this UI. If so, there
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* is a per-thread ringbuffer of requests that ::get_request()
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* just set up a new request in. If so, all we need do here is
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* to advance the write ptr in that ringbuffer so that the next
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* request by this calling thread will use the next slot in
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* the ringbuffer. The ringbuffer has
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* single-reader/single-writer semantics because the calling
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* thread is the only writer, and the UI event loop is the only
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* reader.
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*/
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RequestBuffer* rbuf = per_thread_request_buffer.get ();
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if (rbuf != 0) {
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DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1/%2 send per-thread request type %3\n", name(), pthread_name(), req->type));
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rbuf->increment_write_ptr (1);
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} else {
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/* no per-thread buffer, so just use a list with a lock so that it remains
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single-reader/single-writer semantics
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*/
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DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1/%2 send heap request type %3\n", name(), pthread_name(), req->type));
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Glib::Threads::Mutex::Lock lm (request_list_lock);
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request_list.push_back (req);
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}
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/* send the UI event loop thread a wakeup so that it will look
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at the per-thread and generic request lists.
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*/
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signal_new_request ();
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}
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}
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template<typename RequestObject> void
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AbstractUI<RequestObject>::call_slot (InvalidationRecord* invalidation, const boost::function<void()>& f)
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{
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if (caller_is_self()) {
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DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1/%2 direct dispatch of call slot via functor @ %3, invalidation %4\n", name(), pthread_name(), &f, invalidation));
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f ();
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return;
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}
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RequestObject *req = get_request (BaseUI::CallSlot);
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if (req == 0) {
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return;
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}
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DEBUG_TRACE (PBD::DEBUG::AbstractUI, string_compose ("%1/%2 queue call-slot using functor @ %3, invalidation %4\n", name(), pthread_name(), &f, invalidation));
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/* copy semantics: copy the functor into the request object */
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req->the_slot = f;
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/* the invalidation record is an object which will carry out
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* invalidation of any requests associated with it when it is
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* destroyed. it can be null. if its not null, associate this
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* request with the invalidation record. this allows us to
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* "cancel" requests submitted to the UI because they involved
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* a functor that uses an object that is being deleted.
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*/
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req->invalidation = invalidation;
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if (invalidation) {
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invalidation->requests.push_back (req);
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invalidation->event_loop = this;
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}
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send_request (req);
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}
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