From 082e8fe29206e1f842ab7169ef07c5c144b35968 Mon Sep 17 00:00:00 2001
From: CJ van den Berg <cj@vdbonline.com>
Date: Sat, 20 Apr 2024 23:24:38 +0200
Subject: [PATCH] fix: prevent race on timeout in call()

---
 src/thespian.zig | 46 +++++++++++++++++++++++++++++++---------------
 1 file changed, 31 insertions(+), 15 deletions(-)

diff --git a/src/thespian.zig b/src/thespian.zig
index cd90ddd..2874df3 100644
--- a/src/thespian.zig
+++ b/src/thespian.zig
@@ -689,49 +689,65 @@ const CallContext = struct {
     receiver: ReceiverT,
     to: pid_ref,
     request: message,
-    response: ?message,
+    response: *?message,
     a: std.mem.Allocator,
     mut: std.Thread.Mutex = std.Thread.Mutex{},
     cond: std.Thread.Condition = std.Thread.Condition{},
+    timeout: bool = false,
 
     const Self = @This();
     const ReceiverT = Receiver(*Self);
 
     pub fn call(a: std.mem.Allocator, to: pid_ref, timeout_ns: u64, request: message) error{ OutOfMemory, ThespianSpawnFailed, Timeout }!message {
-        var self: Self = undefined;
-        const rec = ReceiverT.init(receive_, &self);
-
-        self = .{
-            .receiver = rec,
+        var response: ?message = null;
+        var self = try a.create(Self);
+        self.* = .{
+            .receiver = ReceiverT.init(receive_, self),
             .to = to,
             .request = request,
-            .response = null,
+            .response = &response,
             .a = a,
         };
 
         self.mut.lock();
         errdefer self.mut.unlock();
 
-        const proc = try spawn_link(a, &self, start, @typeName(Self));
+        const proc = try spawn_link(a, self, start, @typeName(Self));
         defer proc.deinit();
 
-        try self.cond.timedWait(&self.mut, timeout_ns);
+        self.cond.timedWait(&self.mut, timeout_ns) catch |e| switch (e) {
+            error.Timeout => {
+                self.timeout = true;
+                return e;
+            },
+            else => return e,
+        };
 
-        return self.response orelse .{};
+        return response orelse .{};
+    }
+
+    fn deinit(self: *Self) void {
+        self.a.destroy(self);
     }
 
     fn start(self: *Self) result {
-        errdefer self.cond.signal();
+        errdefer {
+            self.cond.signal();
+            self.deinit();
+        }
         _ = set_trap(true);
         try self.to.link();
         try self.to.send_raw(self.request);
         receive(&self.receiver);
     }
 
-    fn receive_(self: *Self, from: pid_ref, m: message) result {
+    fn receive_(self: *Self, _: pid_ref, m: message) result {
+        defer self.deinit();
         defer self.cond.signal();
-        _ = from;
-        self.response = m.clone(self.a) catch |e| return exit_error(e);
-        try exit_normal();
+        self.mut.lock();
+        defer self.mut.unlock();
+        if (!self.timeout)
+            self.response.* = m.clone(self.a) catch |e| return exit_error(e);
+        return exit_normal();
     }
 };