RE: [RFC] Strange code in cpu_idle()

[Li, Shaohua]

>static void __exit apm_exit(void)
>{
>	int	error;
>
>	if (set_pm_idle) {
>		pm_idle = original_pm_idle;
>		/*
>		 * We are about to unload the current idle thread pm
callback
>		 * (pm_idle), Wait for all processors to update
cached/local
>		 * copies of pm_idle before proceeding.
>		 */
>		synchronize_kernel();
>	}
This patch is written by me. The detail information is in
http://bugzilla.kernel.org/show_bug.cgi?id=1716


>Unfortunately, the idle loop is a quiescent state, so it is
>possible for synchronize_kernel() to return before the idle threads
>have returned.  So I don't believe RCU is useful here.  One other
>approach would be to keep a cpu mask, in which apm_exit() sets all
>bits, and pm_idle() clears its CPU's bit only if it is set.
>Then apm_exit() could wait for all CPU's bits to clear.
This is my original idea. We think it's too complex, so we discard it.
Sorry for my bad.

Thanks,
Shaohua
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