linux-kernel - RE: [patch 3/21] x86, bts: wait until traced task has been scheduled out

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:	Wed, 1 Apr 2009 13:43:26 +0100
From:	"Metzger, Markus T" <markus.t.metzger@...el.com>
To:	Ingo Molnar <mingo@...e.hu>, Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"hpa@...or.com" <hpa@...or.com>,
	"markus.t.metzger@...il.com" <markus.t.metzger@...il.com>,
	"roland@...hat.com" <roland@...hat.com>,
	"eranian@...glemail.com" <eranian@...glemail.com>,
	"Villacis, Juan" <juan.villacis@...el.com>,
	"ak@...ux.jf.intel.com" <ak@...ux.jf.intel.com>
Subject: RE: [patch 3/21] x86, bts: wait until traced task has been
	scheduled out

>-----Original Message-----
>From: Ingo Molnar [mailto:mingo@...e.hu]
>Sent: Wednesday, April 01, 2009 1:42 PM
>To: Oleg Nesterov; Peter Zijlstra


>* Oleg Nesterov <oleg@...hat.com> wrote:
>
>> On 03/31, Markus Metzger wrote:
>> >
>> > +static void wait_to_unschedule(struct task_struct *task)
>> > +{
>> > +	unsigned long nvcsw;
>> > +	unsigned long nivcsw;
>> > +
>> > +	if (!task)
>> > +		return;
>> > +
>> > +	if (task == current)
>> > +		return;
>> > +
>> > +	nvcsw  = task->nvcsw;
>> > +	nivcsw = task->nivcsw;
>> > +	for (;;) {
>> > +		if (!task_is_running(task))
>> > +			break;
>> > +		/*
>> > +		 * The switch count is incremented before the actual
>> > +		 * context switch. We thus wait for two switches to be
>> > +		 * sure at least one completed.
>> > +		 */
>> > +		if ((task->nvcsw - nvcsw) > 1)
>> > +			break;
>> > +		if ((task->nivcsw - nivcsw) > 1)
>> > +			break;
>> > +
>> > +		schedule();
>>
>> schedule() is a nop here. We can wait unpredictably long...
>>
>> Ingo, do have have any ideas to improve this helper?
>
>hm, there's a similar looking existing facility:
>wait_task_inactive(). Have i missed some subtle detail that makes it
>inappropriate for use here?


wait_task_inactive() waits until the task is no longer TASK_RUNNING.

I need to wait until the task has been scheduled out at least once.


regards,
markus.

---------------------------------------------------------------------
Intel GmbH
Dornacher Strasse 1
85622 Feldkirchen/Muenchen Germany
Sitz der Gesellschaft: Feldkirchen bei Muenchen
Geschaeftsfuehrer: Douglas Lusk, Peter Gleissner, Hannes Schwaderer
Registergericht: Muenchen HRB 47456 Ust.-IdNr.
VAT Registration No.: DE129385895
Citibank Frankfurt (BLZ 502 109 00) 600119052

This e-mail and any attachments may contain confidential material for
the sole use of the intended recipient(s). Any review or distribution
by others is strictly prohibited. If you are not the intended
recipient, please contact the sender and delete all copies.

--
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/