linux-kernel - Re: [RFC PATCH v3 07/15] perf workqueue: implement worker thread and management

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Date:   Mon, 30 Aug 2021 09:22:47 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Riccardo Mancini <rickyman7@...il.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Alexey Bayduraev <alexey.v.bayduraev@...ux.intel.com>
Subject: Re: [RFC PATCH v3 07/15] perf workqueue: implement worker thread and
 management

On Fri, Aug 20, 2021 at 12:53:53PM +0200, Riccardo Mancini wrote:

SNIP

>  /**
>   * create_workqueue - create a workqueue associated to @pool
>   *
> @@ -41,7 +361,8 @@ static const char * const workqueue_errno_str[] = {
>   */
>  struct workqueue_struct *create_workqueue(int nr_threads)
>  {
> -	int ret, err = 0;
> +	int ret, err = 0, t;
> +	struct worker *worker;
>  	struct workqueue_struct *wq = zalloc(sizeof(struct workqueue_struct));
>  
>  	if (!wq) {
> @@ -56,10 +377,16 @@ struct workqueue_struct *create_workqueue(int nr_threads)
>  		goto out_free_wq;
>  	}
>  
> +	wq->workers = calloc(nr_threads, sizeof(*wq->workers));
> +	if (!wq->workers) {
> +		err = -ENOMEM;
> +		goto out_delete_pool;
> +	}
> +
>  	ret = pthread_mutex_init(&wq->lock, NULL);
>  	if (ret) {
>  		err = -ret;
> -		goto out_delete_pool;
> +		goto out_free_workers;
>  	}
>  
>  	ret = pthread_cond_init(&wq->idle_cond, NULL);
> @@ -77,12 +404,41 @@ struct workqueue_struct *create_workqueue(int nr_threads)
>  		goto out_destroy_cond;
>  	}
>  
> +	wq->task.fn = worker_thread;
> +
> +	wq->pool_errno = threadpool__execute(wq->pool, &wq->task);
> +	if (wq->pool_errno) {
> +		err = -WORKQUEUE_ERROR__POOLEXE;
> +		goto out_close_pipe;
> +	}

hum, why the threadpool__execute in here? threads are not runnig at this
point, so nothing will happen right?

jirka

> +
> +	for (t = 0; t < nr_threads; t++) {
> +		err = spinup_worker(wq, t);
> +		if (err)
> +			goto out_stop_pool;
> +	}
> +
>  	return wq;
>  
> +out_stop_pool:
> +	lock_workqueue(wq);
> +	for_each_idle_worker(wq, worker) {
> +		ret = stop_worker(worker);
> +		if (ret)
> +			err = ret;
> +	}
> +	unlock_workqueue(wq);
> +out_close_pipe:
> +	close(wq->msg_pipe[0]);
> +	wq->msg_pipe[0] = -1;
> +	close(wq->msg_pipe[1]);
> +	wq->msg_pipe[1] = -1;
>  out_destroy_cond:
>  	pthread_cond_destroy(&wq->idle_cond);
>  out_destroy_mutex:
>  	pthread_mutex_destroy(&wq->lock);
> +out_free_workers:
> +	free(wq->workers);
>  out_delete_pool:
>  	threadpool__delete(wq->pool);
>  out_free_wq:
> @@ -96,12 +452,27 @@ struct workqueue_struct *create_workqueue(int nr_threads)
>   */

SNIP