linux-kernel - RE: [tip:tracing/hw-branch-tracing] tracing/hw-branch-tracing: convert bts-tracer mutex to a spinlock

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: <928CFBE8E7CB0040959E56B4EA41A77E4A4C1F31@irsmsx504.ger.corp.intel.com>
Date:	Wed, 25 Feb 2009 10:08:39 +0000
From:	"Metzger, Markus T" <markus.t.metzger@...el.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	"hpa@...or.com" <hpa@...or.com>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>
Subject: RE: [tip:tracing/hw-branch-tracing] tracing/hw-branch-tracing:
	convert bts-tracer mutex to a spinlock

>-----Original Message-----
>From: Ingo Molnar [mailto:mingo@...e.hu]
>Sent: Wednesday, February 25, 2009 10:58 AM
>To: Metzger, Markus T


>* Metzger, Markus T <markus.t.metzger@...el.com> wrote:
>
>> > static void trace_bts_prepare(struct trace_iterator *iter)
>> > {
>> >-    mutex_lock(&bts_tracer_mutex);
>> >+    spin_lock(&bts_tracer_lock);
>> >
>> >     on_each_cpu(trace_bts_cpu, iter->tr, 1);
>> >
>> >-    mutex_unlock(&bts_tracer_mutex);
>> >+    spin_unlock(&bts_tracer_lock);
>> > }
>>
>> Whereas start/stop are relatively fast, the above operation is
>> rather expensive. Would it make sense to use
>> schedule_on_each_cpu() instead of on_each_cpu()?
>
>it's perfectly fine to do that on_each_cpu() under the spinlock.
>schedule_on_each_cpu() would likely be more expensive - and for
>no good reason.

OK. 

And I assume you like the spinlock better than the
get/put_online_cpus(), as well.

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/