From de949b72c791477c29155ee09a1c5c3d4ab56033 Mon Sep 17 00:00:00 2001 From: Andrew Kelley Date: Tue, 31 Jul 2018 19:57:46 -0400 Subject: [PATCH] simpler std.event.Lock implementation --- std/event/lock.zig | 27 ++------------------------- 1 file changed, 2 insertions(+), 25 deletions(-) diff --git a/std/event/lock.zig b/std/event/lock.zig index 2013b5595f..0bd7183db2 100644 --- a/std/event/lock.zig +++ b/std/event/lock.zig @@ -106,35 +106,12 @@ pub const Lock = struct { // will attempt to grab the lock. _ = @atomicRmw(u8, &self.queue_empty_bit, AtomicRmwOp.Xchg, 0, AtomicOrder.SeqCst); - while (true) { - const old_bit = @atomicRmw(u8, &self.shared_bit, AtomicRmwOp.Xchg, 1, AtomicOrder.SeqCst); - if (old_bit != 0) { - // We did not obtain the lock. Trust that our queue entry will resume us, and allow - // suspend to complete. - break; - } - // We got the lock. However we might have already been resumed from the queue. + const old_bit = @atomicRmw(u8, &self.shared_bit, AtomicRmwOp.Xchg, 1, AtomicOrder.SeqCst); + if (old_bit == 0) { if (self.queue.get()) |node| { // Whether this node is us or someone else, we tail resume it. resume node.data; - break; - } else { - // We already got resumed, and there are none left in the queue, which means that - // we aren't even supposed to hold the lock right now. - _ = @atomicRmw(u8, &self.queue_empty_bit, AtomicRmwOp.Xchg, 1, AtomicOrder.SeqCst); - _ = @atomicRmw(u8, &self.shared_bit, AtomicRmwOp.Xchg, 0, AtomicOrder.SeqCst); - - // There might be a queue item. If we know the queue is empty, we can be done, - // because the other actor will try to obtain the lock. - // But if there's a queue item, we are the actor which must loop and attempt - // to grab the lock again. - if (@atomicLoad(u8, &self.queue_empty_bit, AtomicOrder.SeqCst) == 1) { - break; - } else { - continue; - } } - unreachable; } }