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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <54ac764e.502c1a33.4b4129c3.9dc1b@o2.pl>
Date:	Mon, 04 Jan 2010 00:35:31 +0100
From:	Bartłomiej Zimoń <uzi18@...pl>
To:	linux-kernel@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, awalls@...ix.net,
	danborkmann@...glemail.com, linux-pm@...ts.linux-foundation.org,
	stern@...land.harvard.edu, rjw@...k.pl
Subject: Re: [suspend/resume] Re: userspace notification from module

Dnia 4 stycznia 2010 0:30 "Rafael J. Wysocki" <rjw@...k.pl> napisał(a):

> On Sunday 03 January 2010, Bartłomiej Zimoń wrote:
> > Dnia 3 stycznia 2010 22:29 "Rafael J. Wysocki" <rjw@...k.pl> napisał(a):
> ...
> > 
> > It could be even UIO module but there are no pm events reachable there?
> > 
> > If it is not clean, we must extend pm-utils or write something new
> > (with backends dbus, ipc, scripts, ...)
> > But You see? We still have no information from kernel about events 
> > (especialy resume) or maybe i dont see this ;/
> 
> They are available to the process that tells the kernel to suspend.
> 
> Namely, to tell the kernel to suspend to RAM, the process (call it a power
> manager) needs to (for example) fprintf() "mem" to /sys/power/state.  As soon
> as this happens, the kernel will start to freeze processes (except for the
> power manager itself), so the power manager knows that everything should be
> ready for the suspend before it writes to /sys/power/state.  It doesn't need
> the kernel to tell it when the suspend is going to start, because it _knows_
> that in advance.
> 
> Now, the fprintf() used to trigger the suspend will not return until the resume
> is complete.  So, again, when the fprintf() returns, the power manager will know
> that the resume has just finished (more precisely, the kernel side of it has
> just finished).
> 
> There simply is no need for any special communication between the kernel and
> the power manager.
> 

Thx Rafael - now it clear to me.
And what do You think about sending extra signals to processes?

Best regards.
Bartłomiej Zimoń
PLD Linux, Kadu Team, FreeRunner user
http://kadu-im.blogspot.com/

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/