RT-Thread / RT-Thread/rt-thread
IPC 的 mb 和 mq 无法确保 FIFO
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bug
- Dominant language
- C
- Stars
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- Avg merge
- 4d 12h
- Merged PRs (30d)
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Description
IPC中的 mb 和 mq，在缓冲区已满或者为空时，会把线程 A 挂在等待队列上。
当其他线程 B 读取数据或者发送数据后，会把之前的等待线程 A 唤醒，待线程 A 被调度后再处理数据。
若线程 A 被调度前，有高优先级的线程 C 先被调度，可能导致线程 A 处理数据失败，从而再次进入等待队列。
若 mb 和 mq 是 FIFO 类型，会导致先进入 FIFO 队列的线程 A 晚获取数据；晚进入 FIFO 队列的线程 C 反而先获取到数据。
类似于优先级翻转，这里可能发生 FIFO 翻转。
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by locating the RT-Thread IPC implementations for mb and mq, then trace their full-buffer and empty-buffer wait-queue wake-up and scheduling paths. Reproduce the described priority interaction with three threads and verify whether FIFO waiters can be overtaken; done means the intended FIFO ordering is preserved and covered by a regression test.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- c
- Domain
- embedded-iot, operating-systems
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 32/100