From 0eed7ec9d51fe8c0dd22b72da0130ad9d31877d0 Mon Sep 17 00:00:00 2001 From: Timon Kruiper Date: Wed, 23 Sep 2020 11:41:31 +0200 Subject: [PATCH] Eventloop: Fix deadlock in linux event loop implementation A simple empty main with evented-io would not quit, because some threads were still waiting to be resumed (by the os). The os.write to the eventfd only wakes up one thread and thus there are multiple writes needed to wake up all the other threads. --- lib/std/event/loop.zig | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/lib/std/event/loop.zig b/lib/std/event/loop.zig index 2600b337b37f4dee43403e7f4af90ce93d0a4fa7..bc2eab3c90f7d70f3d9ef31f8c8ce2e50c3c7ca2 100644 --- a/lib/std/event/loop.zig +++ b/lib/std/event/loop.zig @@ -687,9 +687,14 @@ pub const Loop = struct { switch (builtin.os.tag) { .linux => { - // writing 8 bytes to an eventfd cannot fail - const amt = os.write(self.os_data.final_eventfd, &wakeup_bytes) catch unreachable; - assert(amt == wakeup_bytes.len); + // writing to the eventfd will only wake up one thread, thus multiple writes + // are needed to wakeup all the threads + var i: usize = 0; + while (i < self.extra_threads.len + 1) : (i += 1) { + // writing 8 bytes to an eventfd cannot fail + const amt = os.write(self.os_data.final_eventfd, &wakeup_bytes) catch unreachable; + assert(amt == wakeup_bytes.len); + } return; }, .macosx, .freebsd, .netbsd, .dragonfly => { -- 2.54.0