> Don't we need to keep that NULL init? I might be missing something. I wondered the same thing, but on reading it, the cleanup is that he's gotten rid of the need for the entire thing. Previously, there was a mechanism for detecting "wakeup not quite finished" that used a NULL value, but it's no longer needed.
The resultant busy-waiting on the part of the woken-up task was the entire problem this patch aims to fix. So it gets rid of a whole lot of code and barriers. And, as you noticed, the comments explaining them. As the old code explained, the issue is that a task may exit as soon as r_msg is set, so the wakeup procedure has to be: - Ensure r_msg is set to NULL (special-case flag) - Do the wake up - Set r_msg to the final value The woken-up task has to spin as long as r_msg is NULL. Ick. However, a wake_q keeps a reference to a task, so exiting is not a danger. As long as wake_q_add precedes setting r_msg, all is well. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
