关于 signal_task 逻辑的一些疑问

control 调用 signal_task 的时机是创建新任务的时候，通知阻塞的线程来任务了，但是如果实际上没有阻塞的线程，都在工作，是不是就浪费了这次通知呢，那么越繁忙的状态，调用浪费的就越多，进而影响性能呢。

The issue names control and signal_task but does not identify source files or tests. Start by tracing where control calls signal_task, then inspect the task and worker-thread scheduling path. Done means establishing whether notifications are wasted when all threads are busy and documenting or reproducing any measurable performance impact.

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