linux-kernel - Re: BUG: using smp_processor_id() in preemptible [00000000] code: asm/8267

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: <1364393852.5053.74.camel@laptop>
Date:	Wed, 27 Mar 2013 15:17:32 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Joerg Roedel <joro@...tes.org>
Cc:	Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Stephane Eranian <eranian@...gle.com>,
	Namhyung Kim <namhyung.kim@....com>,
	Jiri Olsa <jolsa@...hat.com>, paulmck <paulmck@...ibm.com>
Subject: Re: BUG: using smp_processor_id() in preemptible [00000000] code:
 asm/8267

On Wed, 2013-03-27 at 14:15 +0100, Joerg Roedel wrote:
> What makes me wonder here is that the code is preemptible in an
> rcu_read_locked section. As far as I know preemption needs to be
> disabled while holding the rcu_read_lock().

Nah, a long long time ago some -rt people complained to paulmck that
keeping preemption disabled over all this RCU stuff was killing
latencies. Paul liked the challenge and came up with some mind twisting
stuff to make it work.

If you're into that kind of pain, look at CONFIG_*_PREEMPT_RCU :-)

But yeah, you need to have that stuff enabled before you can hit this
particular snag.

--
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/