From: Jiri Kosina <jkosina@suse.cz>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Rik van Riel <riel@redhat.com>,
linux-kernel@vger.kernel.org, joern@logfs.org,
peterz@infradead.org, cxie@redhat.com,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jslaby@suse.cz>
Subject: Re: [PATCH RFC] sysrq: rcu-ify __handle_sysrq
Date: Wed, 23 Apr 2014 23:39:43 +0200 (CEST) [thread overview]
Message-ID: <alpine.LRH.2.00.1404232338200.1491@twin.jikos.cz> (raw)
In-Reply-To: <20140423130453.32361ca9ceef591b9b184926@linux-foundation.org>
On Wed, 23 Apr 2014, Andrew Morton wrote:
> > Echoing values into /proc/sysrq-trigger seems to be a popular way to
> > get information out of the kernel. However, dumping information about
> > thousands of processes, or hundreds of CPUs to serial console can
> > result in IRQs being blocked for minutes, resulting in various kinds
> > of cascade failures.
> >
> > The most common failure is due to interrupts being blocked for a very
> > long time. This can lead to things like failed IO requests, and other
> > things the system cannot easily recover from.
>
> I bet nobody wants that console output anyway. You do the sysrq then
> run dmesg or look in /var/log/messages to see what happened. People
> who are experiencing problems such as this should run `dmesg -n 1'
> before writing to sysrq-trigger.
I don't agree. I have used sysrq-t multiple times in situations where
userspace was already dead, but sysrq was still able to provide valuable
information about the state of the kernel.
--
Jiri Kosina
SUSE Labs
next prev parent reply other threads:[~2014-04-23 21:39 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-23 16:53 [PATCH RFC] sysrq: rcu-ify __handle_sysrq Rik van Riel
2014-04-23 20:04 ` Andrew Morton
2014-04-23 20:44 ` Rik van Riel
2014-04-23 21:39 ` Jiri Kosina [this message]
2014-04-23 21:41 ` Andrew Morton
2014-04-23 21:44 ` Jiri Kosina
2014-04-23 21:49 ` Andrew Morton
2014-04-23 21:37 ` Jiri Kosina
2014-04-23 21:42 ` Rik van Riel
2014-04-23 21:51 ` Jiri Kosina
2014-04-24 1:46 ` Paul E. McKenney
2014-04-24 13:04 ` [PATCH RFC] sysrq,rcu: suppress RCU stall warnings while sysrq runs Rik van Riel
2014-04-24 15:16 ` Paul E. McKenney
2014-04-25 5:35 ` Mike Galbraith
2014-04-24 0:52 ` [PATCH RFC] sysrq: rcu-ify __handle_sysrq Jörn Engel
2014-04-24 19:40 ` [PATCH] printk: Print cpu number along with time Jörn Engel
2014-04-24 19:58 ` Greg Kroah-Hartman
2014-04-24 21:23 ` Jörn Engel
2014-04-24 22:12 ` Jiri Kosina
2014-04-24 22:18 ` David Rientjes
2014-04-24 22:21 ` Jiri Kosina
2014-04-24 23:29 ` Jörn Engel
2014-04-24 22:20 ` Greg Kroah-Hartman
2014-04-28 23:40 ` Jörn Engel
2014-04-29 0:22 ` Andrew Morton
2014-06-04 23:15 ` Jörn Engel
2014-06-04 23:28 ` Andrew Morton
2014-06-04 23:49 ` Jörn Engel
2014-09-09 17:16 ` Jörn Engel
2014-09-10 21:26 ` Andrew Morton
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