Re: [PATCH 2/2] Fix console handling during suspend/resume

Linus Torvalds
2006-06-15T17:41:21Z

On Thu, 15 Jun 2006, Pavel Machek wrote:
>
> To have DMAs stopped, you need to "freeze" the devices.

No you don't.

You need to stop the high-level _queues_, but that's something totally
different from actually stopping the _devices_.

So, for example, you want to make sure that nobody is writing to the disk
cache, or reading from the disk, or writing to it (apart from the thing
that writes the image, of course) any more.

But that's fundamental: and it has absolutely zero to do with device
suspend (although you do want to tell the device about it - a number of
devices that do polling even in the absense of user input should probably
take the hint from "save your state").

The fact that you equate "suspend the devices" with "stop doing IO" shows
how you think at the wrong level.

The "stop doing IO" is at a much higher level.

Linus