linux-kernel - Re: [PATCH RT] rt: Make cpu_chill() use hrtimer instead of msleep()

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:	Fri, 7 Feb 2014 12:30:06 +0100
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	linux-rt-users <linux-rt-users@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Clark Williams <williams@...hat.com>,
	"Luis Claudio R. Goncalves" <lclaudio@...g.org>,
	John Kacur <jkacur@...hat.com>,
	Ulrich Obergfell <uobergfe@...hat.com>
Subject: Re: [PATCH RT] rt: Make cpu_chill() use hrtimer instead of msleep()

* Steven Rostedt | 2014-02-05 11:51:25 [-0500]:

>Ulrich Obergfell pointed out that cpu_chill() calls msleep() which is woken
>up by the ksoftirqd running the TIMER softirq. But as the cpu_chill() is
>called from softirq context, it may block the ksoftirqd() from running, in
>which case, it may never wake up the msleep() causing the deadlock.
>
>I checked the vmcore, and irq/74-qla2xxx is stuck in the msleep() call,
>running on CPU 8. The one ksoftirqd that is stuck, happens to be the one that
>runs on CPU 8, and it is blocked on a lock held by irq/74-qla2xxx. As that
>ksoftirqd is the one that will wake up irq/74-qla2xxx, and it happens to be
>blocked on a lock that irq/74-qla2xxx holds, we have our deadlock.

could you please tell me which two locks are invovled here?

Sebastian
--
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/