Function broadcast [src]

Unblocks all threads currently blocked in a call to wait() or timedWait() with a given Mutex. The blocked threads must be sequenced before this call with respect to acquiring the same Mutex in order to be observable for unblocking. broadcast() can be called with or without the relevant Mutex being acquired and have no "effect" if there's no observable blocked threads.

Prototype

pub fn broadcast(self: *Condition) void

Parameters

self: *Condition

Example

 test broadcast {
    // This test requires spawning threads
    if (builtin.single_threaded) {
        return error.SkipZigTest;
    }

    const num_threads = 10;

    const BroadcastTest = struct {
        mutex: Mutex = .{},
        cond: Condition = .{},
        completed: Condition = .{},
        count: usize = 0,
        threads: [num_threads]std.Thread = undefined,

        fn run(self: *@This()) void {
            self.mutex.lock();
            defer self.mutex.unlock();

            // The last broadcast thread to start tells the main test thread it's completed.
            self.count += 1;
            if (self.count == num_threads) {
                self.completed.signal();
            }

            // Waits for the count to reach zero after the main test thread observes it at num_threads.
            // Tries to use timedWait() a bit before falling back to wait() to test multiple threads timing out.
            var i: usize = 0;
            while (self.count != 0) : (i +%= 1) {
                if (i < 10) {
                    self.cond.timedWait(&self.mutex, 1) catch {};
                } else {
                    self.cond.wait(&self.mutex);
                }
            }
        }
    };

    var broadcast_test = BroadcastTest{};
    for (&broadcast_test.threads) |*t| {
        t.* = try std.Thread.spawn(.{}, BroadcastTest.run, .{&broadcast_test});
    }

    {
        broadcast_test.mutex.lock();
        defer broadcast_test.mutex.unlock();

        // Wait for all the broadcast threads to spawn.
        // timedWait() to detect any potential deadlocks.
        while (broadcast_test.count != num_threads) {
            broadcast_test.completed.timedWait(
                &broadcast_test.mutex,
                1 * std.time.ns_per_s,
            ) catch {};
        }

        // Reset the counter and wake all the threads to exit.
        broadcast_test.count = 0;
        broadcast_test.cond.broadcast();
    }

    for (broadcast_test.threads) |t| {
        t.join();
    }
}

Source

  pub fn broadcast(self: *Condition) void {
    self.impl.wake(.all);
}  