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thread_safe_bus.state (getter) should not use locks

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評估

難度
4/5
預估耗時
3-5 天
新手友好度
35/100
Issue 類型
缺陷
描述清晰度
基本清楚
活躍度
停滯
技術堆疊
python
領域
networking

研究方向

先閱讀 thread_safe_bus.py 以及 issue 中顯示的 state 屬性,接著追蹤 thread-safe bus 如何使用 send 和 receive 鎖。判斷 state 讀取是否需要獨立於這些鎖的同步;當 state 檢查不再等待 listener,同時在並行 send 和 receive 操作期間仍然安全時,即表示完成。

由索引模型根據 Issue 內容生成。

描述

enhancement
Problem description

I have a small application that listens on one thread, and may send on another (using asyncio). Before sending, I used to check the hardware state by evaluating the .state property. I use the thread safe bus.
However, this leads to long wait phases, depending on incoming messages.

It turns out that getting the .state property locks both send and receive locks, whereas lock_recv is probably occupied by the listener most of the time, which causes the delays.
in thread_safe_bus.py:

    @property
    def state(self):
        with self._lock_send, self._lock_recv:
            return self.__wrapped__.state
Proposed change

I am not very familiar with thread-safe communication in Python, but derived from my C++ knowledge, the value of the .state property is only an enum value and should be atomic anyway, especially when reading.
So from my point of view, I would either just return the value without locks. Or - if any locking is needed for some reason - use a separate state-access-lock that is independent from lock_send and lock_recv.

Workaround

I guess checking the bus state before each send() call is not the correct way to do. I switched to a mere send() and catch a CanError exception afterwards, which works fine without delay.

主要語言
Python
星號
1.6k
分支
701
PR 合併指標
30 天內沒有已合併 PR

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