Commit 0eed7ec9d51fe8c0dd22b72da0130ad9d31877d0 | zig

author	Timon Kruiper <timonkruiper@gmail.com> 2020-09-23 11:41:31+02:00
committer	Timon Kruiper <timonkruiper@gmail.com> 2020-09-23 11:41:31+02:00
log	0eed7ec9d51fe8c0dd22b72da0130ad9d31877d0
tree	edabf258c98ede7cb8d06cfae73e3e9142ac0a48
parent	58ee5f4e61cd9b7a9ba65798e2214efa3753a733

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.

1 files changed, 8 insertions(+), 3 deletions(-)

lib
- std
  - event
    loop.zig

lib/std/event/loop.zig+8-3

 @@ -687,9 +687,14 @@ pub const Loop = struct {
             switch (builtin.os.tag) {
                 .linux => {
-                    // writing 8 bytes to an eventfd cannot fail
+                    // writing to the eventfd will only wake up one thread, thus multiple writes
-                    const amt = os.write(self.os_data.final_eventfd, &wakeup_bytes) catch unreachable;
+                    // are needed to wakeup all the threads
-                    assert(amt == wakeup_bytes.len);
+                    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 => {