Re: shrinking memory for suspend?

[Johannes Berg <johannes@sipsolutions.net>]

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Hi,

> I don't think it's related to the freezing of user space.  You can allocate
> memory with all of the user space frozen just fine.  I'd say it's related to
> the freezing of kernel threads, rather.

Ah, true, of course.

> > Why do we freeze userspace anyway?
> 
> Well, let me quote Linus:
> 
> "I _do_ realize the IO request queue issues, and that we cannot actually do 
> s2ram with some devices in the middle of a DMA. So we want to be able to 
> avoid *that*, there's no question about that. And I suspect that stopping 
> user threads and then waiting for a sync is practically one of the easier 
> ways to do so."

Hmm, yeah. Does this apply to kernel threads too? Actually, I guess
device drivers should wait for suspend and reject commands to devices
that are suspended already? Can it actually happen that we schedule to
userspace while calling all the suspend issues etc?

johannes

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