linux-kernel - Re: [suspend/resume] Re: userspace notification from module

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Date:	Sat, 02 Jan 2010 22:20:55 +0100
From:	Bartłomiej Zimoń <uzi18@...pl>
To:	Andy Walls <awalls@...ix.net>,
	Daniel Borkmann <danborkmann@...glemail.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [suspend/resume] Re: userspace notification from module

Dnia 2 stycznia 2010 19:26 	Bartłomiej Zimoń <uzi18@...pl> napisał(a):
> Dnia 2 stycznia 2010 16:56 	Daniel Borkmann <danborkmann@...glemail.com> napisał(a):
> > Hi Andy,
> > 
> > 2010/1/2 Andy Walls <awalls@...ix.net>:
> > > Why not:
> > >
> > > a. write a module that implements a device node that supports poll(),
> > > and
> > >
> > > b. have a user space process select() on the fd for read or exception
> > > notification
> > >
> > > ?
> > 
> > This is, of course, another possible solution that is more "cleaner"
> > than the one with the signals.
> > Then, your userspace program would have another thread polling for the
> > device node. Question is which timeout would be appropriate to be "CPU
> > friendly" and to keep notification latency short?
> > 
> 
> Just need as fast as possible solution and on the other hand acceptable for kernel sources.
> Usually programs needs just to disconnect something or set one flag.
> Even if program will have no time for this it could be enough just to send this precious info.
> 

first draft: http://starowa.one.pl/~uzi/pld/pm-notify.c

# tail -f /var/log/kernel |grep pm-notify
Jan  2 21:37:19 topijna kernel: pm-notify: suspend prepare
Jan  2 21:38:18 topijna kernel: pm-notify: suspend prepare
Jan  2 21:39:05 topijna kernel: pm-notify: suspend prepare
Jan  2 21:43:38 topijna kernel: pm-notify: suspend prepare
Jan  2 21:51:31 topijna kernel: pm-notify: suspend prepare
Jan  2 21:53:59 topijna kernel: pm-notify: hibernation prepare

But dont know why have loop here:

$ hexdump /dev/test
0000000 0033 0000 0033 0000 0033 0000 0033 0000
*
31424480 0033 0000 0033 0000 0031 0000 0031 0000
31424490 0031 0000 0031 0000 0031 0000 0031 0000
*
$

Best regards.
Barłomiej Zimoń
PLD Linux, Kadu Team

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