linux-kernel - Re: [PATCH 2/8] PM: suspend_block: Add driver to access suspend blockers from user-space

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Date:	Wed, 26 May 2010 12:51:36 +0200
From:	Florian Mickler <florian@...kler.org>
To:	Arve Hjønnevåg <arve@...roid.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Randy Dunlap <rdunlap@...otime.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>,
	Jim Collar <jim.collar@...are.net>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Avi Kivity <avi@...hat.com>, Len Brown <len.brown@...el.com>,
	Pavel Machek <pavel@....cz>, Magnus Damm <damm@...l.co.jp>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	Nigel Cunningham <nigel@...onice.net>,
	linux-doc@...r.kernel.org
Subject: Re: [PATCH 2/8] PM: suspend_block: Add driver to access suspend 
 blockers from user-space

On Wed, 26 May 2010 03:47:27 -0700
Arve Hjønnevåg <arve@...roid.com> wrote:

> 2010/5/26 Peter Zijlstra <peterz@...radead.org>:
> > On Fri, 2010-05-21 at 15:46 -0700, Arve Hjønnevåg wrote:
> >> +To create a suspend blocker from user space, open the suspend_blocker
> >> special
> >> +device file:
> >> +
> >> +    fd = open("/dev/suspend_blocker", O_RDWR | O_CLOEXEC);
> >> +
> >> +then optionally call:
> >> +
> >> +    ioctl(fd, SUSPEND_BLOCKER_IOCTL_SET_NAME(strlen(name)), name);
> >> +
> >> +To activate the suspend blocker call:
> >> +
> >> +    ioctl(fd, SUSPEND_BLOCKER_IOCTL_BLOCK);
> >> +
> >> +To deactivate it call:
> >> +
> >> +    ioctl(fd, SUSPEND_BLOCKER_IOCTL_UNBLOCK);
> >> +
> >> +To destroy the suspend blocker, close the device:
> >> +
> >> +    close(fd);
> >
> > Urgh, please let the open() be BLOCK, the close() be UNBLOCK, and keep
> > the SET_NAME thing if you really care.
> >
> 
> That would be very inefficient.
> 

Also I think it is intended to enforce named suspend blockers. (For
debugging/accounting purposes).

Cheers,
Flo
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