WebRTC RTC publish streams use timer callbacks (SrsRtcPublishRtcpTimer and SrsRtcPublishTwccTimer) that can cause race conditions in SRS's coroutine-based architecture. The timer callbacks are heavy functions that may trigger coroutine switches, during which the timer object can be freed by another coroutine, leading to use-after-free crashes.

The race condition occurs because:

1. Timer callbacks (on_timer) perform heavy operations that can yield control
2. During coroutine switches, other coroutines may destroy the timer object
3. When control returns, the callback continues executing on a freed object

Fixes potential crashes in WebRTC RTC publish streams under high concurrency.