linux-kernel - Re: [PATCH V3] cpuidle: Handle tick_broadcast

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]

Date:	Sat, 09 May 2015 22:11:41 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Cc:	peterz@...radead.org, tglx@...utronix.de,
	rafael.j.wysocki@...el.com, daniel.lezcano@...aro.org,
	rlippert@...gle.com, linux-pm@...r.kernel.org,
	linus.walleij@...aro.org, linux-kernel@...r.kernel.org,
	mingo@...hat.com, sudeep.holla@....com,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH V3] cpuidle: Handle tick_broadcast_enter() failure gracefully

On Saturday, May 09, 2015 11:19:16 AM Preeti U Murthy wrote:
> Hi Rafael,
> 
> On 05/08/2015 07:48 PM, Rafael J. Wysocki wrote:

[cut]

> >>  
> >> +	/* Take note of the planned idle state. */
> >> +	idle_set_state(smp_processor_id(), target_state);
> > 
> > And I wouldn't do this either.
> > 
> > The behavior here is pretty much as though the driver demoted the state chosen
> > by the governor and we don't call idle_set_state() again in those cases.
> 
> Why is this wrong?

It is not "wrong", but incomplete, because demotions done by the cpuidle driver
should also be taken into account in the same way.

But I'm seeing that the recent patch of mine that made cpuidle_enter_state()
call default_idle_call() was a mistake, because it might confuse find_idlest_cpu()
significantly as to what state the CPU is in.  I'll drop that one for now.


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
--
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/