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

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Message-ID: <20141208184035.GE12274@htj.dyndns.org>
Date:	Mon, 8 Dec 2014 13:40:35 -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>
Subject: Re: [PATCH wq/for-3.19 3/3] workqueue: dump workqueues on sysrq-t

Hello, Andrew.

On Mon, Dec 08, 2014 at 10:06:13AM -0800, Andrew Morton wrote:
> sysrq-t already produces thousands of lines of output.  Maybe create a
> new keycode for this?

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.

...
> > +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().

> > +static void pr_cont_work(bool comma, struct work_struct *work)
> > +{
> > +	if (work->func == wq_barrier_func) {
> > +		struct wq_barrier *barr =
> > +			container_of(work, struct wq_barrier, work);
> 
> Can avoid the 80-col contortions with
> 
> 		struct wq_barrier *barr;
> 
> 		barr = container_of(work, struct wq_barrier, work);

I'm not sure either is any better, but sure.

> > +	if (has_in_flight) {
> > +		bool comma = false;
> > +
> > +		printk("    in-flight:");
> 
> pr_something?  show_state() uses KERN_INFO, which may or may not be
> appropriate.

Hmmm, best to match show_state().  I'll convert to pr_info().

Thanks.

-- 
tejun
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