document open(/dev/snapshot) sideeffects -- was Re: [linux-pm]syncing the disks when entering sleep
From: Pavel Machek
Date: Mon Apr 05 2010 - 02:38:43 EST
> > > 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?
Signed-off-by: Pavel Machek <pavel@xxxxxx>
@@ -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
The ioctl() commands recognized by the device are:
SNAPSHOT_FREEZE - freeze user space processes (the current process is
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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