Re: Hotplug events for system suspend/resume

From: Nigel Cunningham
Date: Tue May 11 2004 - 21:19:40 EST


Unless I'm missing something, this will break all existing implementations of
S3 and S4 because they all freeze userspace processes prior to suspending
drivers. They do this because they assume it is the responsibility of
userspace to handle these actions prior to telling the kernel to suspend.

In my mind, this approach is simpler and makes more sense: userspace should
worry about userspace actions related to suspending before calling
kernelspace. Kernel space should then only worry about saving and restoring
driver states and should be transparent to user space. If at resume time,
some devices have really gone away or appeared, hot[un]plugging events can
call userspace then.

One other point: If we have userspace calling kernelspace which calls
userspace, won't we also have to be very careful about not setting up
feedback loops? (Who knows what userspace will do in response to our unplug



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