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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