linux-kernel - Re: [PATCH 19/21] workqueue: introduce worker

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Date:	Tue, 17 Nov 2009 12:51:37 +0100
From:	Louis Rilling <Louis.Rilling@...labs.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	linux-kernel@...r.kernel.org, jeff@...zik.org, mingo@...e.hu,
	akpm@...ux-foundation.org, jens.axboe@...cle.com,
	rusty@...tcorp.com.au, cl@...ux-foundation.org,
	dhowells@...hat.com, arjan@...ux.intel.com,
	torvalds@...ux-foundation.org, avi@...hat.com,
	peterz@...radead.org, andi@...stfloor.org, fweisbec@...il.com
Subject: Re: [PATCH 19/21] workqueue: introduce worker

On 17/11/09 12:39 +0100, Louis Rilling wrote:
> Hi Tejun,
> 
> On 17/11/09  2:15 +0900, Tejun Heo wrote:
> > Separate out worker thread related information to struct worker from
> > struct cpu_workqueue_struct and implement helper functions to deal
> > with the new struct worker.  The only change which is visible outside
> > is that now workqueue worker are all named "kworker/CPUID:WORKERID"
> > where WORKERID is allocated from per-cpu ida.
> > 
> > This is in preparation of concurrency managed workqueue where shared
> > multiple workers would be available per cpu.
> > 
> > Signed-off-by: Tejun Heo <tj@...nel.org>
> > ---
> >  kernel/workqueue.c |  219 +++++++++++++++++++++++++++++++++++++---------------
> >  1 files changed, 157 insertions(+), 62 deletions(-)
> > 
> > diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> > index dce5ad5..6694b3e 100644
> > --- a/kernel/workqueue.c
> > +++ b/kernel/workqueue.c
> 
> [...]
> 
> > @@ -413,6 +426,105 @@ int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
> >  }
> >  EXPORT_SYMBOL_GPL(queue_delayed_work_on);
> >  
> > +static struct worker *alloc_worker(void)
> > +{
> > +	struct worker *worker;
> > +
> > +	worker = kzalloc(sizeof(*worker), GFP_KERNEL);
> > +	return worker;
> > +}
> > +
> > +/**
> > + * create_worker - create a new workqueue worker
> > + * @cwq: cwq the new worker will belong to
> > + * @bind: whether to set affinity to @cpu or not
> > + *
> > + * Create a new worker which is bound to @cwq.  The returned worker
> > + * can be started by calling start_worker() or destroyed using
> > + * destroy_worker().
> > + *
> > + * CONTEXT:
> > + * Might sleep.  Does GFP_KERNEL allocations.
> > + *
> > + * RETURNS:
> > + * Pointer to the newly created worker.
> > + */
> > +static struct worker *create_worker(struct cpu_workqueue_struct *cwq, bool bind)
> > +{
> > +	int id = -1;
> > +	struct worker *worker = NULL;
> > +
> > +	spin_lock(&workqueue_lock);
> > +	while (ida_get_new(&per_cpu(worker_ida, cwq->cpu), &id)) {
> > +		spin_unlock_irq(&workqueue_lock);
> > +		if (!ida_pre_get(&per_cpu(worker_ida, cwq->cpu), GFP_KERNEL))
> > +			goto fail;
> > +		spin_lock(&workqueue_lock);
> > +	}
> > +	spin_unlock_irq(&workqueue_lock);
> > +
> > +	worker = alloc_worker();
> > +	if (!worker)
> > +		goto fail;
> > +
> > +	worker->cwq = cwq;
> > +	worker->id = id;
> > +
> > +	worker->task = kthread_create(worker_thread, worker, "kworker/%u:%d",
> > +				      cwq->cpu, id);
> > +	if (IS_ERR(worker->task))
> > +		goto fail;
> > +
> > +	if (bind)
> > +		kthread_bind(worker->task, cwq->cpu);
> > +
> > +	return worker;
> > +fail:
> > +	if (id >= 0) {
> > +		spin_lock(&workqueue_lock);
> > +		ida_remove(&per_cpu(worker_ida, cwq->cpu), id);
> > +		spin_unlock_irq(&workqueue_lock);
> > +	}
> > +	kfree(worker);
> > +	return NULL;
> > +}
> 
> AFAIU create_worker() should call spin_lock_irq() instead of spin_lock().

spin_unlock() instead of spin_unlock_irq() looks better in fact ;).

Louis

-- 
Dr Louis Rilling			Kerlabs
Skype: louis.rilling			Batiment Germanium
Phone: (+33|0) 6 80 89 08 23		80 avenue des Buttes de Coesmes
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