Zig 0.17.0-dev (Split by item)

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Thread

SmpAllocator.Thread

const Thread = struct

File

lib/std/heap/SmpAllocator.zig:58

Code

const Thread = struct {
    /// Avoid false sharing.
    _: void align(std.atomic.cache_line) = {},

    /// Protects the state in this struct (per-thread state).
    ///
    /// Threads lock this before accessing their own state in order
    /// to support freelist reclamation.
    mutex: std.atomic.Mutex = .unlocked,

    /// For each size class, tracks the next address to be returned from
    /// `alloc` when the freelist is empty.
    next_addrs: [size_class_count]usize = @splat(0),
    /// For each size class, points to the freed pointer.
    frees: [size_class_count]usize = @splat(0),

    fn lock() *Thread {
        var index = thread_index;
        {
            const t = &global.threads[index];
            if (t.mutex.tryLock()) {
                @branchHint(.likely);
                return t;
            }
        }
        const cpu_count = getCpuCount();
        assert(cpu_count != 0);
        while (true) {
            index = (index + 1) % cpu_count;
            const t = &global.threads[index];
            if (t.mutex.tryLock()) {
                thread_index = index;
                return t;
            }
        }
    }

    fn unlock(t: *Thread) void {
        t.mutex.unlock();
    }
}