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From: Andrew Morton <akpm@linux-foundation.org>
To: Jiri Kosina <jkosina@suse.cz>
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 14:41:17 -0700	[thread overview]
Message-ID: <20140423144117.e5ce4b29a272b324b61d512c@linux-foundation.org> (raw)
In-Reply-To: <alpine.LRH.2.00.1404232338200.1491@twin.jikos.cz>

On Wed, 23 Apr 2014 23:39:43 +0200 (CEST) Jiri Kosina <jkosina@suse.cz> wrote:

> 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.
> 

I'm talking about /proc/sysrq-trigger, not the magic key combo.


  reply	other threads:[~2014-04-23 21:41 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
2014-04-23 21:41     ` Andrew Morton [this message]
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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