prevent race condition between speech recognition and SIGCHLD

src/main.zig

@@ -19,6 +19,7 @@ const SpeechHandler = struct {
     recoverable_error_count: u32 = 0,
     exec_program: ?[]const u8 = null,
     child_processes: std.ArrayList(*Process) = .{},
+    reclaiming: std.atomic.Value(bool) = std.atomic.Value(bool).init(false),
 
     const max_children = 5;
     const Process = struct { child: ?*std.process.Child, start: i64, id: std.process.Child.Id }; // why id?
@@ -69,6 +70,10 @@ const SpeechHandler = struct {
     }
 
     fn reclaimProcessesPosix(self: *SpeechHandler, reap_all: bool) !void {
+        // We could end up called by two threads at the same time (via SIGCHLD and an actual speech event)
+        // This code should present that
+        if (self.reclaiming.cmpxchgStrong(false, true, .acquire, .acquire)) |_| return;
+        defer self.reclaiming.store(false, .release);
         if (!reap_all and self.child_processes.items.len <= max_children) return;
         std.log.debug("Reclaiming memory from {s} processes", .{if (reap_all) "ALL" else "completed"});
         if (self.child_processes.items.len == 0) return;