Use `RwMutex` for the `Scope`

7 files changed, 138 insertions, 29 deletions

diff --git a/src/check_decl.cpp b/src/check_decl.cpp
index 66f16546c..4afde6e51 100644
--- a/src/check_decl.cpp
+++ b/src/check_decl.cpp
@@ -381,8 +381,8 @@ gb_internal void override_entity_in_scope(Entity *original_entity, Entity *new_e
 	if (found_scope == nullptr) {
 		return;
 	}
-	mutex_lock(&found_scope->mutex);
-	defer (mutex_unlock(&found_scope->mutex));
+	rw_mutex_lock(&found_scope->mutex);
+	defer (rw_mutex_unlock(&found_scope->mutex));
 
 	// IMPORTANT NOTE(bill, 2021-04-10): Overriding behaviour was flawed in that the
 	// original entity was still used check checked, but the checking was only
@@ -1478,7 +1478,8 @@ gb_internal bool check_proc_body(CheckerContext *ctx_, Token token, DeclInfo *de
 				if (t->kind == Type_Struct) {
 					Scope *scope = t->Struct.scope;
 					GB_ASSERT(scope != nullptr);
-					MUTEX_GUARD_BLOCK(scope->mutex) for (auto const &entry : scope->elements) {
+					rw_mutex_lock(&scope->mutex);
+					for (auto const &entry : scope->elements) {
 						Entity *f = entry.value;
 						if (f->kind == Entity_Variable) {
 							Entity *uvar = alloc_entity_using_variable(e, f->token, f->type, nullptr);
@@ -1488,6 +1489,7 @@ gb_internal bool check_proc_body(CheckerContext *ctx_, Token token, DeclInfo *de
 							array_add(&using_entities, puv);
 						}
 					}
+					rw_mutex_unlock(&scope->mutex);
 				} else {
 					error(e->token, "'using' can only be applied to variables of type struct");
 					break;
@@ -1496,7 +1498,8 @@ gb_internal bool check_proc_body(CheckerContext *ctx_, Token token, DeclInfo *de
 		}
 	}
 
-	MUTEX_GUARD_BLOCK(ctx->scope->mutex) for (auto const &entry : using_entities) {
+	rw_mutex_lock(&ctx->scope->mutex);
+	for (auto const &entry : using_entities) {
 		Entity *e = entry.e;
 		Entity *uvar = entry.uvar;
 		Entity *prev = scope_insert_no_mutex(ctx->scope, uvar);
@@ -1506,6 +1509,7 @@ gb_internal bool check_proc_body(CheckerContext *ctx_, Token token, DeclInfo *de
 			break;
 		}
 	}
+	rw_mutex_unlock(&ctx->scope->mutex);
 
 
 	bool where_clause_ok = evaluate_where_clauses(ctx, nullptr, decl->scope, &decl->proc_lit->ProcLit.where_clauses, !decl->where_clauses_evaluated);
diff --git a/src/check_expr.cpp b/src/check_expr.cpp
index c1787e7b6..d9ab328cb 100644
--- a/src/check_expr.cpp
+++ b/src/check_expr.cpp
@@ -236,10 +236,12 @@ gb_internal void check_did_you_mean_scope(String const &name, Scope *scope, char
 	DidYouMeanAnswers d = did_you_mean_make(heap_allocator(), scope->elements.entries.count, name);
 	defer (did_you_mean_destroy(&d));
 
-	MUTEX_GUARD_BLOCK(&scope->mutex) for (auto const &entry : scope->elements) {
+	rw_mutex_shared_lock(&scope->mutex);
+	for (auto const &entry : scope->elements) {
 		Entity *e = entry.value;
 		did_you_mean_append(&d, e->token.string);
 	}
+	rw_mutex_shared_unlock(&scope->mutex);
 	check_did_you_mean_print(&d, prefix);
 }
 
diff --git a/src/check_stmt.cpp b/src/check_stmt.cpp
index e075297a4..6e84d0789 100644
--- a/src/check_stmt.cpp
+++ b/src/check_stmt.cpp
@@ -622,7 +622,10 @@ gb_internal bool check_using_stmt_entity(CheckerContext *ctx, AstUsingStmt *us,
 
 	case Entity_ImportName: {
 		Scope *scope = e->ImportName.scope;
-		MUTEX_GUARD_BLOCK(scope->mutex) for (auto const &entry : scope->elements) {
+		rw_mutex_lock(&scope->mutex);
+		defer (rw_mutex_unlock(&scope->mutex));
+
+		for (auto const &entry : scope->elements) {
 			String name = entry.key.string;
 			Entity *decl = entry.value;
 			if (!is_entity_exported(decl)) continue;
diff --git a/src/checker.cpp b/src/checker.cpp
index 0075fa543..1d536074d 100644
--- a/src/checker.cpp
+++ b/src/checker.cpp
@@ -51,10 +51,11 @@ gb_internal bool check_rtti_type_disallowed(Ast *expr, Type *type, char const *f
 gb_internal void scope_reset(Scope *scope) {
 	if (scope == nullptr) return;
 
-	MUTEX_GUARD(&scope->mutex);
+	rw_mutex_lock(&scope->mutex);
 	scope->head_child.store(nullptr, std::memory_order_relaxed);
 	string_map_clear(&scope->elements);
 	ptr_set_clear(&scope->imported);
+	rw_mutex_unlock(&scope->mutex);
 }
 
 gb_internal void scope_reserve(Scope *scope, isize capacity) {
@@ -180,9 +181,9 @@ gb_internal void init_decl_info(DeclInfo *d, Scope *scope, DeclInfo *parent) {
 	gb_zero_item(d);
 	d->parent = parent;
 	d->scope  = scope;
-	ptr_set_init(&d->deps);
-	ptr_set_init(&d->type_info_deps);
-	array_init  (&d->labels,         heap_allocator());
+	ptr_set_init(&d->deps, 0);
+	ptr_set_init(&d->type_info_deps, 0);
+	d->labels.allocator = heap_allocator();
 }
 
 gb_internal DeclInfo *make_decl_info(Scope *scope, DeclInfo *parent) {
@@ -394,9 +395,9 @@ gb_internal void scope_lookup_parent(Scope *scope, String const &name, Scope **s
 		StringHashKey key = string_hash_string(name);
 		for (Scope *s = scope; s != nullptr; s = s->parent) {
 			Entity **found = nullptr;
-			mutex_lock(&s->mutex);
+			rw_mutex_shared_lock(&s->mutex);
 			found = string_map_get(&s->elements, key);
-			mutex_unlock(&s->mutex);
+			rw_mutex_shared_unlock(&s->mutex);
 			if (found) {
 				Entity *e = *found;
 				if (gone_thru_proc) {
@@ -482,7 +483,7 @@ gb_internal Entity *scope_insert_with_name(Scope *s, String const &name, Entity
 	Entity **found = nullptr;
 	Entity *result = nullptr;
 
-	MUTEX_GUARD(&s->mutex);
+	rw_mutex_lock(&s->mutex);
 
 	found = string_map_get(&s->elements, key);
 
@@ -509,6 +510,8 @@ gb_internal Entity *scope_insert_with_name(Scope *s, String const &name, Entity
 		entity->scope = s;
 	}
 end:;
+	rw_mutex_unlock(&s->mutex);
+
 	return result;
 }
 
@@ -669,7 +672,8 @@ gb_internal void check_scope_usage(Checker *c, Scope *scope) {
 	Array<VettedEntity> vetted_entities = {};
 	array_init(&vetted_entities, heap_allocator());
 
-	MUTEX_GUARD_BLOCK(scope->mutex) for (auto const &entry : scope->elements) {
+	rw_mutex_shared_lock(&scope->mutex);
+	for (auto const &entry : scope->elements) {
 		Entity *e = entry.value;
 		if (e == nullptr) continue;
 		VettedEntity ve_unused = {};
@@ -686,6 +690,7 @@ gb_internal void check_scope_usage(Checker *c, Scope *scope) {
 			array_add(&vetted_entities, ve_shadowed);
 		}
 	}
+	rw_mutex_shared_unlock(&scope->mutex);
 
 	gb_sort(vetted_entities.data, vetted_entities.count, gb_size_of(VettedEntity), vetted_entity_variable_pos_cmp);
 
diff --git a/src/checker.hpp b/src/checker.hpp
index cc92fce28..53052d5cd 100644
--- a/src/checker.hpp
+++ b/src/checker.hpp
@@ -224,7 +224,7 @@ struct Scope {
 	std::atomic<Scope *> next;
 	std::atomic<Scope *> head_child;
 
-	BlockingMutex mutex;
+	RwMutex mutex;
 	StringMap<Entity *> elements;
 	PtrSet<Scope *> imported;
 
diff --git a/src/thread_pool.cpp b/src/thread_pool.cpp
index 276e93dff..2c369eaad 100644
--- a/src/thread_pool.cpp
+++ b/src/thread_pool.cpp
@@ -47,7 +47,7 @@ gb_internal void thread_pool_destroy(ThreadPool *pool) {
 
 	for_array_off(i, 1, pool->threads) {
 		Thread *t = &pool->threads[i];
-		pool->tasks_available.fetch_add(1, std::memory_order_release);
+		pool->tasks_available.fetch_add(1, std::memory_order_relaxed);
 		futex_broadcast(&pool->tasks_available);
 		thread_join_and_destroy(t);
 	}
@@ -74,7 +74,7 @@ void thread_pool_queue_push(Thread *thread, WorkerTask task) {
 	} while (!thread->head_and_tail.compare_exchange_weak(capture, new_capture));
 
 	thread->pool->tasks_left.fetch_add(1, std::memory_order_release);
-	thread->pool->tasks_available.fetch_add(1, std::memory_order_release);
+	thread->pool->tasks_available.fetch_add(1, std::memory_order_relaxed);
 	futex_broadcast(&thread->pool->tasks_available);
 }
 
@@ -82,7 +82,7 @@ bool thread_pool_queue_pop(Thread *thread, WorkerTask *task) {
 	u64 capture;
 	u64 new_capture;
 	do {
-		capture = thread->head_and_tail.load();
+		capture = thread->head_and_tail.load(std::memory_order_acquire);
 
 		u64 mask = thread->capacity - 1;
 		u64 head = (capture >> 32) & mask;
@@ -97,7 +97,7 @@ bool thread_pool_queue_pop(Thread *thread, WorkerTask *task) {
 		*task = thread->queue[tail];
 
 		new_capture = (head << 32) | new_tail;
-	} while (!thread->head_and_tail.compare_exchange_weak(capture, new_capture));
+	} while (!thread->head_and_tail.compare_exchange_weak(capture, new_capture, std::memory_order_release));
 
 	return true;
 }
@@ -168,22 +168,21 @@ gb_internal THREAD_PROC(thread_pool_thread_proc) {
 
 				Thread *thread = &pool->threads.data[idx];
 				WorkerTask task;
-				if (!thread_pool_queue_pop(thread, &task)) {
-					continue;
-				}
-				task.do_work(task.data);
-				pool->tasks_left.fetch_sub(1, std::memory_order_release);
+				if (thread_pool_queue_pop(thread, &task)) {
+					task.do_work(task.data);
+					pool->tasks_left.fetch_sub(1, std::memory_order_release);
 
-				if (pool->tasks_left.load(std::memory_order_acquire) == 0) {
-					futex_signal(&pool->tasks_left);
-				}
+					if (pool->tasks_left.load(std::memory_order_acquire) == 0) {
+						futex_signal(&pool->tasks_left);
+					}
 
-				goto main_loop_continue;
+					goto main_loop_continue;
+				}
 			}
 		}
 
 		// if we've done all our work, and there's nothing to steal, go to sleep
-		state = pool->tasks_available.load();
+		state = pool->tasks_available.load(std::memory_order_acquire);
 		futex_wait(&pool->tasks_available, state);
 
 		main_loop_continue:;
diff --git a/src/threading.cpp b/src/threading.cpp
index 78943150e..27a17112e 100644
--- a/src/threading.cpp
+++ b/src/threading.cpp
@@ -8,10 +8,12 @@
 
 struct BlockingMutex;
 struct RecursiveMutex;
+struct RwMutex;
 struct Semaphore;
 struct Condition;
 struct Thread;
 struct ThreadPool;
+struct Parker;
 
 #define THREAD_PROC(name) isize name(struct Thread *thread)
 gb_internal THREAD_PROC(thread_pool_thread_proc);
@@ -56,6 +58,13 @@ gb_internal void mutex_lock    (RecursiveMutex *m);
 gb_internal bool mutex_try_lock(RecursiveMutex *m);
 gb_internal void mutex_unlock  (RecursiveMutex *m);
 
+gb_internal void rw_mutex_lock           (RwMutex *m);
+gb_internal bool rw_mutex_try_lock       (RwMutex *m);
+gb_internal void rw_mutex_unlock         (RwMutex *m);
+gb_internal void rw_mutex_shared_lock    (RwMutex *m);
+gb_internal bool rw_mutex_try_shared_lock(RwMutex *m);
+gb_internal void rw_mutex_shared_unlock  (RwMutex *m);
+
 gb_internal void semaphore_post   (Semaphore *s, i32 count);
 gb_internal void semaphore_wait   (Semaphore *s);
 gb_internal void semaphore_release(Semaphore *s) { semaphore_post(s, 1); }
@@ -65,6 +74,10 @@ gb_internal void condition_broadcast(Condition *c);
 gb_internal void condition_signal(Condition *c);
 gb_internal void condition_wait(Condition *c, BlockingMutex *m);
 
+gb_internal void park(Parker *p);
+gb_internal void unpark_one(Parker *p);
+gb_internal void unpark_all(Parker *p);
+
 gb_internal u32  thread_current_id(void);
 
 gb_internal void thread_init                     (ThreadPool *pool, Thread *t, isize idx);
@@ -205,6 +218,30 @@ gb_internal void semaphore_wait(Semaphore *s) {
 	gb_internal void condition_wait(Condition *c, BlockingMutex *m) {
 		SleepConditionVariableSRW(&c->cond, &m->srwlock, INFINITE, 0);
 	}
+
+	struct RwMutex {
+		SRWLOCK srwlock;
+	};
+
+	gb_internal void rw_mutex_lock(RwMutex *m) {
+		AcquireSRWLockExclusive(&m->srwlock);
+	}
+	gb_internal bool rw_mutex_try_lock(RwMutex *m) {
+		return !!TryAcquireSRWLockExclusive(&m->srwlock);
+	}
+	gb_internal void rw_mutex_unlock(RwMutex *m) {
+		ReleaseSRWLockExclusive(&m->srwlock);
+	}
+
+	gb_internal void rw_mutex_shared_lock(RwMutex *m) {
+		AcquireSRWLockShared(&m->srwlock);
+	}
+	gb_internal bool rw_mutex_try_shared_lock(RwMutex *m) {
+		return !!TryAcquireSRWLockShared(&m->srwlock);
+	}
+	gb_internal void rw_mutex_shared_unlock(RwMutex *m) {
+		ReleaseSRWLockShared(&m->srwlock);
+	}
 #else
 	enum Internal_Mutex_State : i32 {
 		Internal_Mutex_State_Unlocked = 0,
@@ -306,8 +343,67 @@ gb_internal void semaphore_wait(Semaphore *s) {
 		futex_wait(&c->state(), state);
 		mutex_lock(m);
 	}
+
+	struct RwMutex {
+		// TODO(bill): make this a proper RW mutex
+		BlockingMutex mutex;
+	};
+
+	gb_internal void rw_mutex_lock(RwMutex *m) {
+		mutex_lock(&m->mutex);
+	}
+	gb_internal bool rw_mutex_try_lock(RwMutex *m) {
+		return mutex_try_lock(&m->mutex);
+	}
+	gb_internal void rw_mutex_unlock(RwMutex *m) {
+		mutex_unlock(&m->mutex);
+	}
+
+	gb_internal void rw_mutex_shared_lock(RwMutex *m) {
+		mutex_lock(&m->mutex);
+	}
+	gb_internal bool rw_mutex_try_shared_lock(RwMutex *m) {
+		return mutex_try_lock(&m->mutex);
+	}
+	gb_internal void rw_mutex_shared_unlock(RwMutex *m) {
+		mutex_unlock(&m->mutex);
+	}
 #endif
 
+struct Parker {
+	Futex state;
+};
+enum ParkerState : u32 {
+	ParkerState_Empty    = 0,
+	ParkerState_Notified = 1,
+	ParkerState_Parked   = UINT32_MAX,
+};
+
+gb_internal void park(Parker *p) {
+	if (p->state.fetch_sub(1, std::memory_order_acquire) == ParkerState_Notified) {
+		return;
+	}
+	for (;;) {
+		futex_wait(&p->state, ParkerState_Parked);
+		i32 notified = ParkerState_Empty;
+		if (p->state.compare_exchange_strong(notified, ParkerState_Empty, std::memory_order_acquire, std::memory_order_acquire)) {
+			return;
+		}
+	}
+}
+
+gb_internal void unpark_one(Parker *p) {
+	if (p->state.exchange(ParkerState_Notified, std::memory_order_release) == ParkerState_Parked) {
+		futex_signal(&p->state);
+	}
+}
+
+gb_internal void unpark_all(Parker *p) {
+	if (p->state.exchange(ParkerState_Notified, std::memory_order_release) == ParkerState_Parked) {
+		futex_broadcast(&p->state);
+	}
+}
+
 
 gb_internal u32 thread_current_id(void) {
 	u32 thread_id;