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// SPDX-License-Identifier: MIT
// Copyright (c) 2015-2020 Zig Contributors
// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
// The MIT license requires this copyright notice to be included in all copies
// and substantial portions of the software.
const std = @import("std");
const ThreadPool = @This();
lock: std.Thread.Mutex = .{},
is_running: bool = true,
allocator: *std.mem.Allocator,
workers: []Worker,
run_queue: RunQueue = .{},
idle_queue: IdleQueue = .{},
const IdleQueue = std.SinglyLinkedList(std.Thread.ResetEvent);
const RunQueue = std.SinglyLinkedList(Runnable);
const Runnable = struct {
runFn: fn (*Runnable) void,
};
const Worker = struct {
pool: *ThreadPool,
thread: *std.Thread,
/// The node is for this worker only and must have an already initialized event
/// when the thread is spawned.
idle_node: IdleQueue.Node,
fn run(worker: *Worker) void {
while (true) {
const held = worker.pool.lock.acquire();
if (worker.pool.run_queue.popFirst()) |run_node| {
held.release();
(run_node.data.runFn)(&run_node.data);
continue;
}
if (worker.pool.is_running) {
worker.idle_node.data.reset();
worker.pool.idle_queue.prepend(&worker.idle_node);
held.release();
worker.idle_node.data.wait();
continue;
}
held.release();
return;
}
}
};
pub fn init(self: *ThreadPool, allocator: *std.mem.Allocator) !void {
self.* = .{
.allocator = allocator,
.workers = &[_]Worker{},
};
if (std.builtin.single_threaded)
return;
const worker_count = std.math.max(1, std.Thread.cpuCount() catch 1);
self.workers = try allocator.alloc(Worker, worker_count);
errdefer allocator.free(self.workers);
var worker_index: usize = 0;
errdefer self.destroyWorkers(worker_index);
while (worker_index < worker_count) : (worker_index += 1) {
const worker = &self.workers[worker_index];
worker.pool = self;
// Each worker requires its ResetEvent to be pre-initialized.
try worker.idle_node.data.init();
errdefer worker.idle_node.data.deinit();
worker.thread = try std.Thread.spawn(worker, Worker.run);
}
}
fn destroyWorkers(self: *ThreadPool, spawned: usize) void {
for (self.workers[0..spawned]) |*worker| {
worker.thread.wait();
worker.idle_node.data.deinit();
}
}
pub fn deinit(self: *ThreadPool) void {
{
const held = self.lock.acquire();
defer held.release();
self.is_running = false;
while (self.idle_queue.popFirst()) |idle_node|
idle_node.data.set();
}
self.destroyWorkers(self.workers.len);
self.allocator.free(self.workers);
}
pub fn spawn(self: *ThreadPool, comptime func: anytype, args: anytype) !void {
if (std.builtin.single_threaded) {
const result = @call(.{}, func, args);
return;
}
const Args = @TypeOf(args);
const Closure = struct {
arguments: Args,
pool: *ThreadPool,
run_node: RunQueue.Node = .{ .data = .{ .runFn = runFn } },
fn runFn(runnable: *Runnable) void {
const run_node = @fieldParentPtr(RunQueue.Node, "data", runnable);
const closure = @fieldParentPtr(@This(), "run_node", run_node);
const result = @call(.{}, func, closure.arguments);
const held = closure.pool.lock.acquire();
defer held.release();
closure.pool.allocator.destroy(closure);
}
};
const held = self.lock.acquire();
defer held.release();
const closure = try self.allocator.create(Closure);
closure.* = .{
.arguments = args,
.pool = self,
};
self.run_queue.prepend(&closure.run_node);
if (self.idle_queue.popFirst()) |idle_node|
idle_node.data.set();
}
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