linux-kernel - Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <1274981127.27810.5597.camel@twins>
Date:	Thu, 27 May 2010 19:25:27 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Florian Mickler <florian@...kler.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Arve Hjønnevåg <arve@...roid.com>,
	Vitaly Wool <vitalywool@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Paul@...p1.linux-foundation.org, felipe.balbi@...ia.com,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	Linux PM <linux-pm@...ts.linux-foundation.org>
Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

On Thu, 2010-05-27 at 19:21 +0200, Florian Mickler wrote:
> On Thu, 27 May 2010 18:45:25 +0200 (CEST)
> Thomas Gleixner <tglx@...utronix.de> wrote:
> 
> > The whole notion of treating suspend to RAM any different than a plain
> > idle C-State is wrong. It's not different at all. You just use a
> > different mechanism which has longer takedown and wakeup latencies and
> > requires to shut down stuff and setup extra wakeup sources.
> > 
> > And there is the whole problem. Switching from normal event delivery
> > to those special wakeup sources. That needs to be engineered in any
> > case carefuly and it does not matter whether you add suspend blockers
> > or not.
> 
> Ok, I just don't know the answer: How is it just another idle state if
> the userspace gets frozen? Doesn't that bork the whole transition and
> you need a userspace<->kernel synchronisation point to not loose events?

There is no userspace to freeze when the runqueues are empty.

And as explained, you won't loose events if all the devices do a proper
state transition. To quote:

On Thu, 2010-05-27 at 18:45 +0200, Thomas Gleixner wrote:
> If the interrupt happens _BEFORE_ we switch over to the quiescent
> state, then we need to backout. If it happens after the switch then it
> goes into the nirwana if the suspend wakeup has not been set up
> correctly. If we have it setup correctly then we go into suspend just
> to come back immediately. There is nothing you can do about that with
> suspend blockers.
> 

--
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/