linux-kernel - Re: [PATCH wq/for-3.19 3/3] workqueue: dump workqueues on sysrq-t

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Message-ID: <20141208192229.GF12274@htj.dyndns.org>
Date:	Mon, 8 Dec 2014 14:22:29 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Lai Jiangshan <laijs@...fujitsu.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH wq/for-3.19 3/3] workqueue: dump workqueues on sysrq-t

(cc'ing Greg for tty)

On Mon, Dec 08, 2014 at 11:05:15AM -0800, Andrew Morton wrote:
> > Believe it or not, we already used up all alphanumerics if we count in
> > the arch-specific ones.  Given that the workqueue information would
> > primarily be useful in tracking down hangs and we'd want to see the
> > dump of tasks in that case anyway, sysrq-t isn't a bad fit for
> > appending workqueue dump.  If anybody has a better idea, I'm all ears.
> 
> Really.  Upper case?

Greg, would using uppercase chars for sysrq work over the different
types of ttys?

> > > > +static void pr_cont_pool_info(struct worker_pool *pool)
> > > > +{
> > > > +	if (pool->cpu >= 0)
> > > > +		pr_cont(" cpu=%d", pool->cpu);
> > > > +	else if (pool->node != NUMA_NO_NODE)
> > > > +		pr_cont(" node=%d", pool->node);
> > > > +
> > > > +	if (pool->cpu < 0) {
> > > > +		static char cpus_buf[PAGE_SIZE];
> > > 
> > > Ouch.  This could be [NR_CPUS + epsilon]?
> > 
> > It's bitmap mask printing so each char can show four cpus.  PAGE_SIZE
> > should be enough for now but I think we need cpumask_prcont().
> 
> I'm not concerned about it being too small ;) Not many people have 16k
> CPUs - can it be shrunk?  It's particularly gross when CONFIG_SMP=n!

Heh, lemme just go ahead and implement bitmap_pr_cont() and
cpumask_pr_cont().

Thanks.

-- 
tejun
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