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Merge pull request #6453 from kristoff-it/fix-futures

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Fix std.event.Future
This commit is contained in:
Alexandros Naskos 2020-09-29 15:56:21 +03:00 committed by GitHub
commit c98d55626d
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2 changed files with 12 additions and 8 deletions
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2
lib/std/event/future.zig
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@ -95,7 +95,7 @@ test "std.event.Future" {
// TODO provide a way to run tests in evented I/O mode
if (!std.io.is_async) return error.SkipZigTest;
const handle = async testFuture();
testFuture();
}
fn testFuture() void {

18
lib/std/event/lock.zig
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@ -27,20 +27,24 @@ pub const Lock = struct {
const Waiter = struct {
// forced Waiter alignment to ensure it doesn't clash with LOCKED
next: ?*Waiter align(2),
next: ?*Waiter align(2),
tail: *Waiter,
node: Loop.NextTickNode,
};
pub fn initLocked() Lock {
return Lock{ .head = LOCKED };
}
pub fn acquire(self: *Lock) Held {
const held = self.mutex.acquire();
// self.head transitions from multiple stages depending on the value:
// UNLOCKED -> LOCKED:
// UNLOCKED -> LOCKED:
// acquire Lock ownership when theres no waiters
// LOCKED -> <Waiter head ptr>:
// Lock is already owned, enqueue first Waiter
// <head ptr> -> <head ptr>:
// <head ptr> -> <head ptr>:
// Lock is owned with pending waiters. Push our waiter to the queue.
if (self.head == UNLOCKED) {
@ -51,7 +55,7 @@ pub const Lock = struct {
var waiter: Waiter = undefined;
waiter.next = null;
waiter.tail = &waiter;
waiter.tail = &waiter;
const head = switch (self.head) {
UNLOCKED => unreachable,
@ -79,15 +83,15 @@ pub const Lock = struct {
}
pub const Held = struct {
lock: *Lock,
lock: *Lock,
pub fn release(self: Held) void {
const waiter = blk: {
const held = self.lock.mutex.acquire();
defer held.release();
// self.head goes through the reverse transition from acquire():
// <head ptr> -> <new head ptr>:
// <head ptr> -> <new head ptr>:
// pop a waiter from the queue to give Lock ownership when theres still others pending
// <head ptr> -> LOCKED:
// pop the laster waiter from the queue, while also giving it lock ownership when awaken