linux-kernel - Re: [PATCH v1 2/3] async: Introduce async_schedule_dev

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Date: Thu, 28 Dec 2023 21:29:45 +0100
From: Stanislaw Gruszka <stanislaw.gruszka@...ux.intel.com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Greg KH <gregkh@...uxfoundation.org>, linux-pm@...r.kernel.org,
	Youngmin Nam <youngmin.nam@...sung.com>, rafael@...nel.org,
	linux-kernel@...r.kernel.org, d7271.choe@...sung.com,
	janghyuck.kim@...sung.com, hyesoo.yu@...sung.com,
	Alan Stern <stern@...land.harvard.edu>,
	Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH v1 2/3] async: Introduce async_schedule_dev_nocall()

On Wed, Dec 27, 2023 at 09:38:23PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> In preparation for subsequent changes, introduce a specialized variant
> of async_schedule_dev() that will not invoke the argument function
> synchronously when it cannot be scheduled for asynchronous execution.
> 
> The new function, async_schedule_dev_nocall(), will be used for fixing
> possible deadlocks in the system-wide power management core code.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/base/power/main.c |   12 ++++++++----
>  include/linux/async.h     |    2 ++
>  kernel/async.c            |   29 +++++++++++++++++++++++++++++
>  3 files changed, 39 insertions(+), 4 deletions(-)
> 
> Index: linux-pm/kernel/async.c
> ===================================================================
> --- linux-pm.orig/kernel/async.c
> +++ linux-pm/kernel/async.c
> @@ -244,6 +244,35 @@ async_cookie_t async_schedule_node(async
>  EXPORT_SYMBOL_GPL(async_schedule_node);
>  
>  /**
> + * async_schedule_dev_nocall - A simplified variant of async_schedule_dev()
> + * @func: function to execute asynchronously
> + * @dev: device argument to be passed to function
> + *
> + * @dev is used as both the argument for the function and to provide NUMA
> + * context for where to run the function.
> + *
> + * If the asynchronous execution of @func is scheduled successfully, return
> + * true. Otherwise, do nothing and return false, unlike async_schedule_dev()
> + * that will run the function synchronously then.
> + */
> +bool async_schedule_dev_nocall(async_func_t func, struct device *dev)
> +{
> +	struct async_entry *entry;
> +
> +	entry = kzalloc(sizeof(struct async_entry), GFP_KERNEL);

Is GFP_KERNEL intended here ? I think it's not safe since will
be called from device_resume_noirq() .

Regards
Stanislaw