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Merge pull request godotengine#96593 from RandomShaper/res_changed_mu…
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…ltiverse

ResourceLoader: Add thread-aware resource changed mechanism
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@akien-mga
akien-mga committed Sep 6, 2024
2 parents c2d81b0 + 74b9c38 commit 05d9854
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Showing 3 changed files with 139 additions and 49 deletions.
22 changes: 11 additions & 11 deletions core/io/resource.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -40,12 +40,12 @@
#include <stdio.h>

void Resource::emit_changed() {
if (ResourceLoader::is_within_load() && MessageQueue::get_main_singleton() != MessageQueue::get_singleton() && !MessageQueue::get_singleton()->is_flushing()) {
// Let the connection happen on the call queue, later, since signals are not thread-safe.
call_deferred("emit_signal", CoreStringName(changed));
} else {
emit_signal(CoreStringName(changed));
if (ResourceLoader::is_within_load() && !Thread::is_main_thread()) {
ResourceLoader::resource_changed_emit(this);
return;
}

emit_signal(CoreStringName(changed));
}

void Resource::_resource_path_changed() {
Expand Down Expand Up @@ -166,22 +166,22 @@ bool Resource::editor_can_reload_from_file() {
}

void Resource::connect_changed(const Callable &p_callable, uint32_t p_flags) {
if (ResourceLoader::is_within_load() && MessageQueue::get_main_singleton() != MessageQueue::get_singleton() && !MessageQueue::get_singleton()->is_flushing()) {
// Let the check and connection happen on the call queue, later, since signals are not thread-safe.
callable_mp(this, &Resource::connect_changed).call_deferred(p_callable, p_flags);
if (ResourceLoader::is_within_load() && !Thread::is_main_thread()) {
ResourceLoader::resource_changed_connect(this, p_callable, p_flags);
return;
}

if (!is_connected(CoreStringName(changed), p_callable) || p_flags & CONNECT_REFERENCE_COUNTED) {
connect(CoreStringName(changed), p_callable, p_flags);
}
}

void Resource::disconnect_changed(const Callable &p_callable) {
if (ResourceLoader::is_within_load() && MessageQueue::get_main_singleton() != MessageQueue::get_singleton() && !MessageQueue::get_singleton()->is_flushing()) {
// Let the check and disconnection happen on the call queue, later, since signals are not thread-safe.
callable_mp(this, &Resource::disconnect_changed).call_deferred(p_callable);
if (ResourceLoader::is_within_load() && !Thread::is_main_thread()) {
ResourceLoader::resource_changed_disconnect(this, p_callable);
return;
}

if (is_connected(CoreStringName(changed), p_callable)) {
disconnect(CoreStringName(changed), p_callable);
}
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150 changes: 113 additions & 37 deletions core/io/resource_loader.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@
#include "resource_loader.h"

#include "core/config/project_settings.h"
#include "core/core_bind.h"
#include "core/io/file_access.h"
#include "core/io/resource_importer.h"
#include "core/object/script_language.h"
Expand Down Expand Up @@ -234,17 +235,22 @@ void ResourceLoader::LoadToken::clear() {
// User-facing tokens shouldn't be deleted until completely claimed.
DEV_ASSERT(user_rc == 0 && user_path.is_empty());

if (!local_path.is_empty()) { // Empty is used for the special case where the load task is not registered.
DEV_ASSERT(thread_load_tasks.has(local_path));
ThreadLoadTask &load_task = thread_load_tasks[local_path];
if (load_task.task_id && !load_task.awaited) {
task_to_await = load_task.task_id;
if (!local_path.is_empty()) {
if (task_if_unregistered) {
memdelete(task_if_unregistered);
task_if_unregistered = nullptr;
} else {
DEV_ASSERT(thread_load_tasks.has(local_path));
ThreadLoadTask &load_task = thread_load_tasks[local_path];
if (load_task.task_id && !load_task.awaited) {
task_to_await = load_task.task_id;
}
// Removing a task which is still in progress would be catastrophic.
// Tokens must be alive until the task thread function is done.
DEV_ASSERT(load_task.status == THREAD_LOAD_FAILED || load_task.status == THREAD_LOAD_LOADED);
thread_load_tasks.erase(local_path);
}
// Removing a task which is still in progress would be catastrophic.
// Tokens must be alive until the task thread function is done.
DEV_ASSERT(load_task.status == THREAD_LOAD_FAILED || load_task.status == THREAD_LOAD_LOADED);
thread_load_tasks.erase(local_path);
local_path.clear();
local_path.clear(); // Mark as already cleared.
}
}

Expand Down Expand Up @@ -324,6 +330,9 @@ void ResourceLoader::_run_load_task(void *p_userdata) {
}
}

ThreadLoadTask *curr_load_task_backup = curr_load_task;
curr_load_task = &load_task;

// Thread-safe either if it's the current thread or a brand new one.
CallQueue *own_mq_override = nullptr;
if (load_nesting == 0) {
Expand Down Expand Up @@ -451,6 +460,8 @@ void ResourceLoader::_run_load_task(void *p_userdata) {
}
DEV_ASSERT(load_paths_stack.is_empty());
}

curr_load_task = curr_load_task_backup;
}

static String _validate_local_path(const String &p_path) {
Expand Down Expand Up @@ -521,9 +532,7 @@ Ref<ResourceLoader::LoadToken> ResourceLoader::_load_start(const String &p_path,

Ref<LoadToken> load_token;
bool must_not_register = false;
ThreadLoadTask unregistered_load_task; // Once set, must be valid up to the call to do the load.
ThreadLoadTask *load_task_ptr = nullptr;
bool run_on_current_thread = false;
{
MutexLock thread_load_lock(thread_load_mutex);

Expand Down Expand Up @@ -578,22 +587,19 @@ Ref<ResourceLoader::LoadToken> ResourceLoader::_load_start(const String &p_path,
}
}

// If we want to ignore cache, but there's another task loading it, we can't add this one to the map and we also have to finish within scope.
// If we want to ignore cache, but there's another task loading it, we can't add this one to the map.
must_not_register = ignoring_cache && thread_load_tasks.has(local_path);
if (must_not_register) {
load_token->local_path.clear();
unregistered_load_task = load_task;
load_task_ptr = &unregistered_load_task;
load_token->task_if_unregistered = memnew(ThreadLoadTask(load_task));
load_task_ptr = load_token->task_if_unregistered;
} else {
DEV_ASSERT(!thread_load_tasks.has(local_path));
HashMap<String, ResourceLoader::ThreadLoadTask>::Iterator E = thread_load_tasks.insert(local_path, load_task);
load_task_ptr = &E->value;
}
}

run_on_current_thread = must_not_register || p_thread_mode == LOAD_THREAD_FROM_CURRENT;

if (run_on_current_thread) {
if (p_thread_mode == LOAD_THREAD_FROM_CURRENT) {
// The current thread may happen to be a thread from the pool.
WorkerThreadPool::TaskID tid = WorkerThreadPool::get_singleton()->get_caller_task_id();
if (tid != WorkerThreadPool::INVALID_TASK_ID) {
Expand All @@ -606,11 +612,8 @@ Ref<ResourceLoader::LoadToken> ResourceLoader::_load_start(const String &p_path,
}
} // MutexLock(thread_load_mutex).

if (run_on_current_thread) {
if (p_thread_mode == LOAD_THREAD_FROM_CURRENT) {
_run_load_task(load_task_ptr);
if (must_not_register) {
load_token->res_if_unregistered = load_task_ptr->resource;
}
}

return load_token;
Expand Down Expand Up @@ -738,7 +741,10 @@ Ref<Resource> ResourceLoader::_load_complete_inner(LoadToken &p_load_token, Erro
*r_error = OK;
}

if (!p_load_token.local_path.is_empty()) {
ThreadLoadTask *load_task_ptr = nullptr;
if (p_load_token.task_if_unregistered) {
load_task_ptr = p_load_token.task_if_unregistered;
} else {
if (!thread_load_tasks.has(p_load_token.local_path)) {
if (r_error) {
*r_error = ERR_BUG;
Expand Down Expand Up @@ -809,22 +815,47 @@ Ref<Resource> ResourceLoader::_load_complete_inner(LoadToken &p_load_token, Erro
load_task.error = FAILED;
}

Ref<Resource> resource = load_task.resource;
if (r_error) {
*r_error = load_task.error;
}
return resource;
} else {
// Special case of an unregistered task.
// The resource should have been loaded by now.
Ref<Resource> resource = p_load_token.res_if_unregistered;
if (!resource.is_valid()) {
if (r_error) {
*r_error = FAILED;
load_task_ptr = &load_task;
}

Ref<Resource> resource = load_task_ptr->resource;
if (r_error) {
*r_error = load_task_ptr->error;
}

if (resource.is_valid()) {
if (curr_load_task) {
// A task awaiting another => Let the awaiter accumulate the resource changed connections.
DEV_ASSERT(curr_load_task != load_task_ptr);
for (const ThreadLoadTask::ResourceChangedConnection &rcc : load_task_ptr->resource_changed_connections) {
curr_load_task->resource_changed_connections.push_back(rcc);
}
} else {
// A leaf task being awaited => Propagate the resource changed connections.
if (Thread::is_main_thread()) {
// On the main thread it's safe to migrate the connections to the standard signal mechanism.
for (const ThreadLoadTask::ResourceChangedConnection &rcc : load_task_ptr->resource_changed_connections) {
if (rcc.callable.is_valid()) {
rcc.source->connect_changed(rcc.callable, rcc.flags);
}
}
} else {
// On non-main threads, we have to queue and call it done when processed.
if (!load_task_ptr->resource_changed_connections.is_empty()) {
for (const ThreadLoadTask::ResourceChangedConnection &rcc : load_task_ptr->resource_changed_connections) {
if (rcc.callable.is_valid()) {
MessageQueue::get_main_singleton()->push_callable(callable_mp(rcc.source, &Resource::connect_changed).bind(rcc.callable, rcc.flags));
}
}
core_bind::Semaphore done;
MessageQueue::get_main_singleton()->push_callable(callable_mp(&done, &core_bind::Semaphore::post));
done.wait();
}
}
}
return resource;
}

return resource;
}

bool ResourceLoader::_ensure_load_progress() {
Expand All @@ -838,6 +869,50 @@ bool ResourceLoader::_ensure_load_progress() {
return true;
}

void ResourceLoader::resource_changed_connect(Resource *p_source, const Callable &p_callable, uint32_t p_flags) {
print_lt(vformat("%d\t%ud:%s\t" FUNCTION_STR "\t%d", Thread::get_caller_id(), p_source->get_instance_id(), p_source->get_class(), p_callable.get_object_id()));

MutexLock lock(thread_load_mutex);

for (const ThreadLoadTask::ResourceChangedConnection &rcc : curr_load_task->resource_changed_connections) {
if (unlikely(rcc.source == p_source && rcc.callable == p_callable)) {
return;
}
}

ThreadLoadTask::ResourceChangedConnection rcc;
rcc.source = p_source;
rcc.callable = p_callable;
rcc.flags = p_flags;
curr_load_task->resource_changed_connections.push_back(rcc);
}

void ResourceLoader::resource_changed_disconnect(Resource *p_source, const Callable &p_callable) {
print_lt(vformat("%d\t%ud:%s\t" FUNCTION_STR "t%d", Thread::get_caller_id(), p_source->get_instance_id(), p_source->get_class(), p_callable.get_object_id()));

MutexLock lock(thread_load_mutex);

for (uint32_t i = 0; i < curr_load_task->resource_changed_connections.size(); ++i) {
const ThreadLoadTask::ResourceChangedConnection &rcc = curr_load_task->resource_changed_connections[i];
if (unlikely(rcc.source == p_source && rcc.callable == p_callable)) {
curr_load_task->resource_changed_connections.remove_at_unordered(i);
return;
}
}
}

void ResourceLoader::resource_changed_emit(Resource *p_source) {
print_lt(vformat("%d\t%ud:%s\t" FUNCTION_STR, Thread::get_caller_id(), p_source->get_instance_id(), p_source->get_class()));

MutexLock lock(thread_load_mutex);

for (const ThreadLoadTask::ResourceChangedConnection &rcc : curr_load_task->resource_changed_connections) {
if (unlikely(rcc.source == p_source)) {
rcc.callable.call();
}
}
}

Ref<Resource> ResourceLoader::ensure_resource_ref_override_for_outer_load(const String &p_path, const String &p_res_type) {
ERR_FAIL_COND_V(load_nesting == 0, Ref<Resource>()); // It makes no sense to use this from nesting level 0.
const String &local_path = _validate_local_path(p_path);
Expand Down Expand Up @@ -1368,6 +1443,7 @@ bool ResourceLoader::timestamp_on_load = false;
thread_local int ResourceLoader::load_nesting = 0;
thread_local Vector<String> ResourceLoader::load_paths_stack;
thread_local HashMap<int, HashMap<String, Ref<Resource>>> ResourceLoader::res_ref_overrides;
thread_local ResourceLoader::ThreadLoadTask *ResourceLoader::curr_load_task = nullptr;

SafeBinaryMutex<ResourceLoader::BINARY_MUTEX_TAG> &_get_res_loader_mutex() {
return ResourceLoader::thread_load_mutex;
Expand Down
16 changes: 15 additions & 1 deletion core/io/resource_loader.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -106,6 +106,8 @@ class ResourceLoader {
MAX_LOADERS = 64
};

struct ThreadLoadTask;

public:
enum ThreadLoadStatus {
THREAD_LOAD_INVALID_RESOURCE,
Expand All @@ -124,7 +126,7 @@ class ResourceLoader {
String local_path;
String user_path;
uint32_t user_rc = 0; // Having user RC implies regular RC incremented in one, until the user RC reaches zero.
Ref<Resource> res_if_unregistered;
ThreadLoadTask *task_if_unregistered = nullptr;

void clear();

Expand Down Expand Up @@ -187,13 +189,21 @@ class ResourceLoader {
Ref<Resource> resource;
bool use_sub_threads = false;
HashSet<String> sub_tasks;

struct ResourceChangedConnection {
Resource *source = nullptr;
Callable callable;
uint32_t flags = 0;
};
LocalVector<ResourceChangedConnection> resource_changed_connections;
};

static void _run_load_task(void *p_userdata);

static thread_local int load_nesting;
static thread_local HashMap<int, HashMap<String, Ref<Resource>>> res_ref_overrides; // Outermost key is nesting level.
static thread_local Vector<String> load_paths_stack;
static thread_local ThreadLoadTask *curr_load_task;

static SafeBinaryMutex<BINARY_MUTEX_TAG> thread_load_mutex;
friend SafeBinaryMutex<BINARY_MUTEX_TAG> &_get_res_loader_mutex();
Expand All @@ -214,6 +224,10 @@ class ResourceLoader {

static bool is_within_load() { return load_nesting > 0; };

static void resource_changed_connect(Resource *p_source, const Callable &p_callable, uint32_t p_flags);
static void resource_changed_disconnect(Resource *p_source, const Callable &p_callable);
static void resource_changed_emit(Resource *p_source);

static Ref<Resource> load(const String &p_path, const String &p_type_hint = "", ResourceFormatLoader::CacheMode p_cache_mode = ResourceFormatLoader::CACHE_MODE_REUSE, Error *r_error = nullptr);
static bool exists(const String &p_path, const String &p_type_hint = "");

Expand Down

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