From ed36dbbd9c9dc21b2eebae1b31586fea1c6b51c3 Mon Sep 17 00:00:00 2001 From: Andrew Kelley Date: Wed, 25 Sep 2019 23:35:41 -0400 Subject: mv std/ lib/ that's all this commit does. further commits will fix cli flags and such. see #2221 --- lib/std/spinlock.zig | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) create mode 100644 lib/std/spinlock.zig (limited to 'lib/std/spinlock.zig') diff --git a/lib/std/spinlock.zig b/lib/std/spinlock.zig new file mode 100644 index 0000000000..905460a2d0 --- /dev/null +++ b/lib/std/spinlock.zig @@ -0,0 +1,32 @@ +const std = @import("std.zig"); +const builtin = @import("builtin"); +const AtomicOrder = builtin.AtomicOrder; +const AtomicRmwOp = builtin.AtomicRmwOp; +const assert = std.debug.assert; + +pub const SpinLock = struct { + lock: u8, // TODO use a bool or enum + + pub const Held = struct { + spinlock: *SpinLock, + + pub fn release(self: Held) void { + assert(@atomicRmw(u8, &self.spinlock.lock, builtin.AtomicRmwOp.Xchg, 0, AtomicOrder.SeqCst) == 1); + } + }; + + pub fn init() SpinLock { + return SpinLock{ .lock = 0 }; + } + + pub fn acquire(self: *SpinLock) Held { + while (@atomicRmw(u8, &self.lock, builtin.AtomicRmwOp.Xchg, 1, AtomicOrder.SeqCst) != 0) {} + return Held{ .spinlock = self }; + } +}; + +test "spinlock" { + var lock = SpinLock.init(); + const held = lock.acquire(); + defer held.release(); +} -- cgit v1.2.3