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const std = @import("std");
const builtin = @import("builtin");
const Pool = @This();
const WaitGroup = @import("WaitGroup.zig");
mutex: std.Thread.Mutex = .{},
cond: std.Thread.Condition = .{},
run_queue: RunQueue = .{},
is_running: bool = true,
allocator: std.mem.Allocator,
threads: []std.Thread,
const RunQueue = std.SinglyLinkedList(Runnable);
const Runnable = struct {
runFn: RunProto,
};
const RunProto = *const fn (*Runnable) void;
pub const Options = struct {
allocator: std.mem.Allocator,
n_jobs: ?u32 = null,
};
pub fn init(pool: *Pool, options: Options) !void {
const allocator = options.allocator;
pool.* = .{
.allocator = allocator,
.threads = &[_]std.Thread{},
};
if (builtin.single_threaded) {
return;
}
const thread_count = options.n_jobs orelse @max(1, std.Thread.getCpuCount() catch 1);
pool.threads = try allocator.alloc(std.Thread, thread_count);
errdefer allocator.free(pool.threads);
// kill and join any threads we spawned previously on error.
var spawned: usize = 0;
errdefer pool.join(spawned);
for (pool.threads) |*thread| {
thread.* = try std.Thread.spawn(.{}, worker, .{pool});
spawned += 1;
}
}
pub fn deinit(pool: *Pool) void {
pool.join(pool.threads.len); // kill and join all threads.
pool.* = undefined;
}
fn join(pool: *Pool, spawned: usize) void {
if (builtin.single_threaded) {
return;
}
{
pool.mutex.lock();
defer pool.mutex.unlock();
// ensure future worker threads exit the dequeue loop
pool.is_running = false;
}
// wake up any sleeping threads (this can be done outside the mutex)
// then wait for all the threads we know are spawned to complete.
pool.cond.broadcast();
for (pool.threads[0..spawned]) |thread| {
thread.join();
}
pool.allocator.free(pool.threads);
}
pub fn spawn(pool: *Pool, comptime func: anytype, args: anytype) !void {
if (builtin.single_threaded) {
@call(.auto, func, args);
return;
}
const Args = @TypeOf(args);
const Closure = struct {
arguments: Args,
pool: *Pool,
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);
@call(.auto, func, closure.arguments);
// The thread pool's allocator is protected by the mutex.
const mutex = &closure.pool.mutex;
mutex.lock();
defer mutex.unlock();
closure.pool.allocator.destroy(closure);
}
};
{
pool.mutex.lock();
defer pool.mutex.unlock();
const closure = try pool.allocator.create(Closure);
closure.* = .{
.arguments = args,
.pool = pool,
};
pool.run_queue.prepend(&closure.run_node);
}
// Notify waiting threads outside the lock to try and keep the critical section small.
pool.cond.signal();
}
fn worker(pool: *Pool) void {
pool.mutex.lock();
defer pool.mutex.unlock();
while (true) {
while (pool.run_queue.popFirst()) |run_node| {
// Temporarily unlock the mutex in order to execute the run_node
pool.mutex.unlock();
defer pool.mutex.lock();
const runFn = run_node.data.runFn;
runFn(&run_node.data);
}
// Stop executing instead of waiting if the thread pool is no longer running.
if (pool.is_running) {
pool.cond.wait(&pool.mutex);
} else {
break;
}
}
}
pub fn waitAndWork(pool: *Pool, wait_group: *WaitGroup) void {
while (!wait_group.isDone()) {
if (blk: {
pool.mutex.lock();
defer pool.mutex.unlock();
break :blk pool.run_queue.popFirst();
}) |run_node| {
run_node.data.runFn(&run_node.data);
continue;
}
wait_group.wait();
return;
}
}
|
