input/curl: hold mutex while writing to postponed_error

src/input/AsyncInputStream.cxx

@@ -63,6 +63,16 @@ AsyncInputStream::Pause()
 	paused = true;
 }
 
+void
+AsyncInputStream::PostponeError(Error &&error)
+{
+	assert(io_thread_inside());
+
+	seek_state = SeekState::NONE;
+	postponed_error = std::move(error);
+	cond.broadcast();
+}
+
 inline void
 AsyncInputStream::Resume()
 {

src/input/AsyncInputStream.hxx

@@ -86,6 +86,8 @@ protected:
 		open = false;
 	}
 
+	void PostponeError(Error &&error);
+
 	bool IsBufferEmpty() const {
 		return buffer.IsEmpty();
 	}

src/input/plugins/CurlInputPlugin.cxx

@@ -777,9 +777,10 @@ CurlInputStream::DoSeek(offset_type new_offset)
 		return;
 	}
 
+	Error error;
 	if (!InitEasy(postponed_error)) {
 		mutex.lock();
-		SeekDone();
+		PostponeError(std::move(error));
 		return;
 	}
 
@@ -790,9 +791,9 @@ CurlInputStream::DoSeek(offset_type new_offset)
 		curl_easy_setopt(easy, CURLOPT_RANGE, range);
 	}
 
-	if (!input_curl_easy_add_indirect(this, postponed_error)) {
+	if (!input_curl_easy_add_indirect(this, error)) {
 		mutex.lock();
-		SeekDone();
+		PostponeError(std::move(error));
 		return;
 	}