From 0809b95a4868147547ab5f5a6560cc8ccb4e16f6 Mon Sep 17 00:00:00 2001
From: Jorijn van der Graaf <jorijnvdgraaf@catcrafts.net>
Date: Wed, 2 Sep 2026 22:19:08 +0200
Subject: [PATCH] An operation ends when the client says so, not when its
 status says done

fprintd's contract: a status with done=true means no more status is coming,
not that the operation is over. The client still calls EnrollStop or
VerifyStop, and until it does the device is busy with that operation. Clearing
the op on done made every stock client's Stop fail with NoActionInProgress --
seen on the first fprintd-enroll against this daemon, which otherwise succeeded
through all ten stages.

Clearing it from the worker was also a race: a client that cancels and
immediately starts a new operation would have had that new operation cleared by
the old one's completion event. The worker no longer touches the op state at
all; only Stop and Release do, on the main thread.
---
 implementations/main.cpp | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/implementations/main.cpp b/implementations/main.cpp
index 6577884..b06423a 100644
--- a/implementations/main.cpp
+++ b/implementations/main.cpp
@@ -1330,7 +1330,7 @@ struct Job {
 // Everything the worker sends back to the main thread. Delivered by g_idle_add
 // so the D-Bus emission happens on the thread that owns the connection.
 struct Event {
-    enum class Kind { Ready, StartFailed, ClaimDone, EnrollStatus, VerifyStatus, OpFinished } kind;
+    enum class Kind { Ready, StartFailed, ClaimDone, EnrollStatus, VerifyStatus } kind;
     bool ok = false;
     bool done = false;
     std::string status;
@@ -1430,7 +1430,6 @@ private:
                 else                   ev->status = "enroll-failed";
                 if (!o.why.empty()) std::println("enrolment: {}", o.why);
                 PostEvent(std::move(ev));
-                PostEvent(std::make_unique<Event>(Event{ .kind = Event::Kind::OpFinished }));
                 break;
             }
             case Job::Kind::Verify: {
@@ -1443,7 +1442,6 @@ private:
                 else if (o.matched)    ev->status = "verify-match";
                 else                   ev->status = "verify-no-match";
                 PostEvent(std::move(ev));
-                PostEvent(std::make_unique<Event>(Event{ .kind = Event::Kind::OpFinished }));
                 break;
             }
             }
@@ -1646,10 +1644,6 @@ void PostEvent(std::unique_ptr<Event> ev) {
             if (ev->done && ev->status == "verify-match")
                 std::println("verified fid {} for uid {}", ev->fid, g_claim.uid);
             break;
-        case Event::Kind::OpFinished:
-            g_claim.op = Op::None;
-            g_claim.finger.clear();
-            break;
         }
         return G_SOURCE_REMOVE;
     }, ev.release());
@@ -1825,7 +1819,14 @@ void HandleDevice(GDBusMethodInvocation* inv, std::string_view method, GVariant*
             ReturnError(inv, "NoActionInProgress", "no such operation in progress");
             return;
         }
+        // The operation is over when the CLIENT says so. A `done` status only
+        // means no more status is coming; fprintd's clients call Stop after
+        // it, and clearing the op ourselves on `done` made every one of them
+        // fail with NoActionInProgress. Cancelling a loop that already ended
+        // is harmless.
         g_worker->CancelOp();
+        g_claim.op = Op::None;
+        g_claim.finger.clear();
         g_dbus_method_invocation_return_value(inv, nullptr);
         return;
     }