godot/core/command_queue_mt.cpp
Lyuma f994666bbe core/command_queue_mt: Fix crash/hang when buffer fills up
This patch fixes two related issues. One is the race condition in issue #42107..
The other is a crash which happens when the reader is lapped near the end of the buffer.

Backport of 48e8da4 to 3.2
2020-10-21 16:39:54 -07:00

140 lines
4.2 KiB
C++

/*************************************************************************/
/* command_queue_mt.cpp */
/*************************************************************************/
/* This file is part of: */
/* GODOT ENGINE */
/* https://godotengine.org */
/*************************************************************************/
/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur. */
/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md). */
/* */
/* Permission is hereby granted, free of charge, to any person obtaining */
/* a copy of this software and associated documentation files (the */
/* "Software"), to deal in the Software without restriction, including */
/* without limitation the rights to use, copy, modify, merge, publish, */
/* distribute, sublicense, and/or sell copies of the Software, and to */
/* permit persons to whom the Software is furnished to do so, subject to */
/* the following conditions: */
/* */
/* The above copyright notice and this permission notice shall be */
/* included in all copies or substantial portions of the Software. */
/* */
/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
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/*************************************************************************/
#include "command_queue_mt.h"
#include "core/os/os.h"
#include "core/project_settings.h"
void CommandQueueMT::lock() {
if (mutex)
mutex->lock();
}
void CommandQueueMT::unlock() {
if (mutex)
mutex->unlock();
}
void CommandQueueMT::wait_for_flush() {
// wait one millisecond for a flush to happen
OS::get_singleton()->delay_usec(1000);
}
CommandQueueMT::SyncSemaphore *CommandQueueMT::_alloc_sync_sem() {
int idx = -1;
while (true) {
lock();
for (int i = 0; i < SYNC_SEMAPHORES; i++) {
if (!sync_sems[i].in_use) {
sync_sems[i].in_use = true;
idx = i;
break;
}
}
unlock();
if (idx == -1) {
wait_for_flush();
} else {
break;
}
}
return &sync_sems[idx];
}
bool CommandQueueMT::dealloc_one() {
tryagain:
if (dealloc_ptr == (write_ptr_and_epoch >> 1)) {
// The queue is empty
return false;
}
uint32_t size = *(uint32_t *)&command_mem[dealloc_ptr];
if (size == 0) {
// End of command buffer wrap down
dealloc_ptr = 0;
goto tryagain;
}
if (size & 1) {
// Still used, nothing can be deallocated
return false;
}
dealloc_ptr += (size >> 1) + 8;
return true;
}
CommandQueueMT::CommandQueueMT(bool p_sync) {
read_ptr_and_epoch = 0;
write_ptr_and_epoch = 0;
dealloc_ptr = 0;
mutex = Mutex::create();
command_mem_size = GLOBAL_DEF_RST("memory/limits/command_queue/multithreading_queue_size_kb", DEFAULT_COMMAND_MEM_SIZE_KB);
ProjectSettings::get_singleton()->set_custom_property_info("memory/limits/command_queue/multithreading_queue_size_kb", PropertyInfo(Variant::INT, "memory/limits/command_queue/multithreading_queue_size_kb", PROPERTY_HINT_RANGE, "1,4096,1,or_greater"));
command_mem_size *= 1024;
command_mem = (uint8_t *)memalloc(command_mem_size);
for (int i = 0; i < SYNC_SEMAPHORES; i++) {
sync_sems[i].sem = Semaphore::create();
sync_sems[i].in_use = false;
}
if (p_sync) {
sync = Semaphore::create();
} else {
sync = NULL;
}
}
CommandQueueMT::~CommandQueueMT() {
if (sync)
memdelete(sync);
memdelete(mutex);
for (int i = 0; i < SYNC_SEMAPHORES; i++) {
memdelete(sync_sems[i].sem);
}
memfree(command_mem);
}