1 files changed, 15 insertions, 2 deletions
diff --git a/src/ninep/tree.zig b/src/ninep/tree.zig
index bc32ad33..c9e7b31a 100644
--- a/src/ninep/tree.zig
+++ b/src/ninep/tree.zig
@@ -122,6 +122,8 @@ pub const Open = struct {
         event: bool,
         /// The one open reading a pane's pty/data.
         pty_data,
+        /// An open that may write a pane's ctl, and so hold its lock.
+        ctl,
     } = .{ .snapshot = null },
     /// A read that found nothing yet (`.again`), kept to be answered when
     /// this open's file has something, the way factotum keeps its log's
@@ -141,7 +143,7 @@ pub const Open = struct {
             .snapshot => |bytes| if (bytes) |b| gpa.free(b),
             .log => |log| gpa.free(log.bytes),
             .run => |run| gpa.free(run.output),
-            .event, .pty_data => {},
+            .event, .pty_data, .ctl => {},
         }
         o.* = .{};
     }
@@ -577,6 +579,10 @@ fn open(p: *Pardes, req: Req, target: Target) Reply {
                 .event => if (reader and pn.fs.event_reader) return failText(req.tag, E.BUSY, e_in_use) else .{ .event = reader },
                 .pty_data => if (!reader) return .{ .tag = req.tag } else if (pn.fs.pty_reader) return failText(req.tag, E.BUSY, e_in_use) else .pty_data,
                 .pty_run => .{ .run = .{} },
+                .ctl => switch (req.omode & 3) {
+                    1, 2 => .ctl, // OWRITE, ORDWR
+                    else => return .{ .tag = req.tag },
+                },
                 else => return .{ .tag = req.tag },
             };
         },
@@ -605,7 +611,7 @@ fn open(p: *Pardes, req: Req, target: Target) Reply {
             pn.fs.event_reader = pn.fs.event_reader or reader;
         },
         .pty_data => pane_of.?.fs.pty_reader = true,
-        .run => {},
+        .run, .ctl => {},
     }
     return .{ .tag = req.tag, .handle = @intCast(i + 1) };
 }
@@ -652,6 +658,13 @@ fn releaseHandle(p: *Pardes, req: Req) void {
         .run => if (pn.fs.run == @as(u8, @intCast(req.handle - 1))) {
             pn.fs.run = null;
         },
+        // Closing the open that holds the lock gives it up, as acme's clunk
+        // of its ctlfid does (editors/acme/xfid.c:211); a write parked on
+        // `lock` goes again.
+        .ctl => if (pn.fs.lock == @as(u8, @intCast(req.handle - 1))) {
+            pn.fs.lock = null;
+            pardes.turn.parked = true;
+        },
         .snapshot, .log => {},
     };
     o.deinit(p.gpa);