Re: document open(/dev/snapshot) sideeffects -- was Re: syncing the disks when entering sleep

Rafael J. Wysocki
2010-04-23T18:28:55Z

On Monday 05 April 2010, Pavel Machek wrote:
> Hi!
>
> > > > Please note that merely _opening_ /dev/snapshot has side effects, so that's
> > > > not just "three ioctls".
> > >
> > > I search Doc*/power/userland-swsusp.txt, and could not find mentions
> > > of sideeffects. Perhaps that should be fixed?
> >
> > Please feel free to make the docs more complete, then.
>
> Yes, something like this?

Yes, looks reasonable.

I've applied it to suspend-2.6/linux-next (added a changelog).

Rafael

> Signed-off-by: Pavel Machek <pavel@ucw.cz>
>
> --- a/Documentation/power/userland-swsusp.txt
> +++ b/Documentation/power/userland-swsusp.txt
> @@ -24,6 +24,10 @@ assumed to be in the resume mode. The device cannot be open for simultaneous
> reading and writing. It is also impossible to have the device open more than
> once at a time.
>
> +Even opening the device has side effects. Data structures are
> +allocated, and PM_HIBERNATION_PREPARE / PM_RESTORE_PREPARE chains are
> +called.
> +
> The ioctl() commands recognized by the device are:
>
> SNAPSHOT_FREEZE - freeze user space processes (the current process is
>
>
>
>