linux-kernel - Re: [PATCH 2/2] sysrq,rcu: suppress RCU stall warnings while sysrq runs

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Date:	Thu, 15 May 2014 16:48:50 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	riel@...hat.com, linux-kernel@...r.kernel.org,
	rdunlap@...radead.org, richard@....at, umgwanakikbuti@...il.com
Subject: Re: [PATCH 2/2] sysrq,rcu: suppress RCU stall warnings while sysrq
 runs

On Thu, May 15, 2014 at 04:24:12PM -0700, Andrew Morton wrote:
> On Tue, 29 Apr 2014 14:06:36 -0400 riel@...hat.com wrote:
> 
> > From: Rik van Riel <riel@...hat.com>
> > 
> > Some sysrq handlers can run for a long time, because they dump a lot
> > of data onto a serial console. Having RCU stall warnings pop up in
> > the middle of them only makes the problem worse.
> > 
> > This patch temporarily disables RCU stall warnings while a sysrq
> > request is handled.
> >
> > ...
> >
> >  drivers/tty/sysrq.c      |  3 +++
> >  include/linux/rcupdate.h | 12 ++++++++++++
> >  kernel/rcu/update.c      | 12 ++++++++++++
> 
> OK, what's going on here.  Someone (of, I suspect, a Paulish nature)
> has plucked out the rcu parts of this patch, put them in linux-next and
> omitted the drivers/tty part.  Very tricky!

Sounds like something I might do...  ;-)

I intend to push this for the upcoming merge window, in case it matters.

> I have done the opposite and have staged two patches against linux-next:
> 
> http://ozlabs.org/~akpm/mmots/broken-out/sysrq-rcu-ify-__handle_sysrq.patch

I defer to Rik for this one.

> http://ozlabs.org/~akpm/mmots/broken-out/sysrqrcu-suppress-rcu-stall-warnings-while-sysrq-runs.patch

The "[paulmck@...ux.vnet.ibm.com: fix TINY_RCU build error]" should be
removed, since it goes with the patch I queued.  Not that it matters
that much, I suppose.

							Thanx, Paul

> Please check, review, comment, etc.
> 

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