linux-kernel - [PATCH v3 ] remoteproc: Use unbounded workqueue for recovery work

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Date:   Thu, 14 Apr 2022 17:44:17 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Mukesh Ojha <quic_mojha@...cinc.com>
Cc:     linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        bjorn.andersson@...aro.org, mathieu.poirier@...aro.org,
        Saravana Kannan <saravanak@...gle.com>, kernel-team@...roid.com
Subject: [PATCH v3 ] remoteproc: Use unbounded workqueue for recovery work

Mukesh Ojha <quic_mojha@...cinc.com> wrote:
> There could be a scenario where there is too much load on a core
> (n number of tasks which is affined) or in a case when multiple
> rproc subsystem is going for a recovery and they queued recovery
> work to one core so even though subsystem are independent there
> recovery will be delayed if one of the subsystem recovery work
> is taking more time in completing.
> 
> If we make this queue unbounded, the recovery work could be picked
> on any cpu. This patch try to address this.
> 
> Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
> ---
> Changes in v3:
>   - Add fallback option to go back to earlier path incase recovery wq
>     creation fails.
> 
> Changes in v2:
>   - Removed WQ_HIGHPRI.
>   - Updated commit text.
> 
>  drivers/remoteproc/remoteproc_core.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index c510125..6446c84 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -59,6 +59,7 @@ static int rproc_release_carveout(struct rproc *rproc,
>  
>  /* Unique indices for remoteproc devices */
>  static DEFINE_IDA(rproc_dev_index);
> +static struct workqueue_struct *rproc_recovery_wq;
>  
>  static const char * const rproc_crash_names[] = {
>  	[RPROC_MMUFAULT]	= "mmufault",
> @@ -2755,8 +2756,11 @@ void rproc_report_crash(struct rproc *rproc, enum rproc_crash_type type)
>  	dev_err(&rproc->dev, "crash detected in %s: type %s\n",
>  		rproc->name, rproc_crash_to_string(type));
>  
> -	/* Have a worker handle the error; ensure system is not suspended */
> -	queue_work(system_freezable_wq, &rproc->crash_handler);
> +	if (rproc_recovery_wq)
> +		queue_work(rproc_recovery_wq, &rproc->crash_handler);
> +	else
> +		queue_work(system_freezable_wq, &rproc->crash_handler);

This is unnecessarily complicated. If you can't create a workqueue you
have bigger problems with the system. Just stick with the new rproc
workqueue.

> +
>  }
>  EXPORT_SYMBOL(rproc_report_crash);
>  
> @@ -2805,6 +2809,11 @@ static void __exit rproc_exit_panic(void)
>  
>  static int __init remoteproc_init(void)
>  {
> +	rproc_recovery_wq = alloc_workqueue("rproc_recovery_wq",
> +						WQ_UNBOUND | WQ_FREEZABLE, 0);
> +	if (!rproc_recovery_wq)
> +		pr_err("remoteproc: creation of rproc_recovery_wq failed\n");

Fail the init if you can't create a workqueue.

> +
>  	rproc_init_sysfs();
>  	rproc_init_debugfs();
>  	rproc_init_cdev();
> @@ -2821,6 +2830,8 @@ static void __exit remoteproc_exit(void)
>  	rproc_exit_panic();
>  	rproc_exit_debugfs();
>  	rproc_exit_sysfs();
> +	if (rproc_recovery_wq)
> +		destroy_workqueue(rproc_recovery_wq);

Will need a fix here too.

-Saravana

>  }
>  module_exit(remoteproc_exit);
>  
> -- 
> 2.7.4