linux-kernel - Re: [PATCH 5/9] usb: don't use PREPARE_DELAYED

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Date:	Thu, 20 Feb 2014 12:59:21 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Tejun Heo <tj@...nel.org>, Alan Stern <stern@...land.harvard.edu>
Cc:	laijs@...fujitsu.com, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org
Subject: Re: [PATCH 5/9] usb: don't use PREPARE_DELAYED_WORK

On Thu, Feb 20, 2014 at 03:44:27PM -0500, Tejun Heo wrote:
> PREPARE_[DELAYED_]WORK() are being phased out.  They have few users
> and a nasty surprise in terms of reentrancy guarantee as workqueue
> considers work items to be different if they don't have the same work
> function.
> 
> usb_hub->init_work is multiplexed with multiple work functions.
> Introduce hub_init_workfn() which invokes usb_hub->init_workfn and
> always use it as the work function and update the users to set the
> ->init_workfn field instead of overriding the work function using
> PREPARE_DELAYED_WORK().
> 
> It looks like that the work items are never queued while in-flight, so
> simply using INIT_DELAYED_WORK() before each queueing could be enough.
> This patch performs equivalent conversion just in case but we probably
> wanna clean it up later if that's the case.

I think it should be fine to use INIT_DELAYED_WORK(), but Alan would
know best.  Alan?

> 
> It would probably be best to route this with other related updates
> through the workqueue tree.
> 
> Lightly tested.
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: linux-usb@...r.kernel.org

Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

> ---
>  drivers/usb/core/hub.c | 13 ++++++++++---
>  drivers/usb/core/hub.h |  1 +
>  2 files changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 64ea219..2bc61c0 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -1040,7 +1040,7 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
>  		 */
>  		if (type == HUB_INIT) {
>  			delay = hub_power_on(hub, false);
> -			PREPARE_DELAYED_WORK(&hub->init_work, hub_init_func2);
> +			hub->init_workfn = hub_init_func2;
>  			schedule_delayed_work(&hub->init_work,
>  					msecs_to_jiffies(delay));
>  
> @@ -1194,7 +1194,7 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
>  
>  		/* Don't do a long sleep inside a workqueue routine */
>  		if (type == HUB_INIT2) {
> -			PREPARE_DELAYED_WORK(&hub->init_work, hub_init_func3);
> +			hub->init_workfn = hub_init_func3;
>  			schedule_delayed_work(&hub->init_work,
>  					msecs_to_jiffies(delay));
>  			return;		/* Continues at init3: below */
> @@ -1634,6 +1634,13 @@ static void hub_disconnect(struct usb_interface *intf)
>  	kref_put(&hub->kref, hub_release);
>  }
>  
> +static void hub_init_workfn(struct work_struct *work)
> +{
> +	struct usb_hub *hub = container_of(to_delayed_work(work),
> +					   struct usb_hub, init_work);
> +	hub->init_workfn(work);
> +}
> +
>  static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id)
>  {
>  	struct usb_host_interface *desc;
> @@ -1728,7 +1735,7 @@ descriptor_error:
>  	hub->intfdev = &intf->dev;
>  	hub->hdev = hdev;
>  	INIT_DELAYED_WORK(&hub->leds, led_work);
> -	INIT_DELAYED_WORK(&hub->init_work, NULL);
> +	INIT_DELAYED_WORK(&hub->init_work, hub_init_workfn);
>  	usb_get_intf(intf);
>  
>  	usb_set_intfdata (intf, hub);
> diff --git a/drivers/usb/core/hub.h b/drivers/usb/core/hub.h
> index df629a3..ef81463 100644
> --- a/drivers/usb/core/hub.h
> +++ b/drivers/usb/core/hub.h
> @@ -72,6 +72,7 @@ struct usb_hub {
>  	unsigned		has_indicators:1;
>  	u8			indicator[USB_MAXCHILDREN];
>  	struct delayed_work	leds;
> +	work_func_t		init_workfn;
>  	struct delayed_work	init_work;
>  	struct usb_port		**ports;
>  };
> -- 
> 1.8.5.3
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