Re: Hotplug events for system suspend/resume
From: Todd Poynor
Date: Tue May 11 2004 - 21:47:17 EST
Nigel Cunningham wrote:
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.
The patch hooks into the power subsystem prior to freezing processes and
after unfreezing processes, so I don't think it's a concern (unless
something is using the power subsystem rather oddly). This patch sends
a single notification of system suspend and a single notification of
system resume, in case there's any confusion with the individual device
state change notifiers also recently discussed. It's been run
successfully on one ACPI system and one non-ACPI system.
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. ...
Agreed, with the minor reservations listed in a previous email (suspend
initiated by drivers must coordinate ad-hoc with userspace, etc.).
I'll let anybody who cares more deeply about this speak up now,
otherwise this isn't a battle I'll be fighting on behalf of others any
more. Thanks -- Todd
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