linux-kernel - Re: [PATCH v4 10/10] ntb_perf: clear link_is

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Message-ID: <1466110623.16234.279.camel@intel.com>
Date:	Thu, 16 Jun 2016 20:57:20 +0000
From:	"Jiang, Dave" <dave.jiang@...el.com>
To:	"Allen.Hubbe@....com" <Allen.Hubbe@....com>,
	"logang@...tatee.com" <logang@...tatee.com>,
	"jdmason@...zu.us" <jdmason@...zu.us>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"shuahkh@....samsung.com" <shuahkh@....samsung.com>,
	"sudipm.mukherjee@...il.com" <sudipm.mukherjee@...il.com>,
	"linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
	"arnd@...db.de" <arnd@...db.de>,
	"linux-ntb@...glegroups.com" <linux-ntb@...glegroups.com>
Subject: Re: [PATCH v4 10/10] ntb_perf: clear link_is_up flag when the link
 goes down.

On Thu, 2016-06-16 at 14:17 -0600, Logan Gunthorpe wrote:
> When the link goes down, the link_is_up flag did not return to
> false. This could have caused some subtle corner case bugs
> when the link goes up and down quickly.
> 
> Once that was fixed, there was found to be a race if the link was
> brought down then immediately up. The link_cleanup work would
> occasionally be scheduled after the next link up event. This would
> cancel the link_work that was supposed to occur and leave ntb_perf
> in an unusable state.
> 
> To fix this we get rid of the link_cleanup work and put the actions
> directly in the link_down event.
> 
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>

Acked-by: Dave Jiang <dave.jiang@...el.com>

Also patches 1-3 Acked. 

> ---
>  drivers/ntb/test/ntb_perf.c | 28 +++++++++-------------------
>  1 file changed, 9 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/ntb/test/ntb_perf.c
> b/drivers/ntb/test/ntb_perf.c
> index f0784e5..6a50f20 100644
> --- a/drivers/ntb/test/ntb_perf.c
> +++ b/drivers/ntb/test/ntb_perf.c
> @@ -133,7 +133,6 @@ struct perf_ctx {
>  	spinlock_t		db_lock;
>  	struct perf_mw		mw;
>  	bool			link_is_up;
> -	struct work_struct	link_cleanup;
>  	struct delayed_work	link_work;
>  	wait_queue_head_t	link_wq;
>  	struct dentry		*debugfs_node_dir;
> @@ -158,10 +157,16 @@ static void perf_link_event(void *ctx)
>  {
>  	struct perf_ctx *perf = ctx;
>  
> -	if (ntb_link_is_up(perf->ntb, NULL, NULL) == 1)
> +	if (ntb_link_is_up(perf->ntb, NULL, NULL) == 1) {
>  		schedule_delayed_work(&perf->link_work, 2*HZ);
> -	else
> -		schedule_work(&perf->link_cleanup);
> +	} else {
> +		dev_dbg(&perf->ntb->pdev->dev, "link down\n");
> +
> +		if (!perf->link_is_up)
> +			cancel_delayed_work_sync(&perf->link_work);
> +
> +		perf->link_is_up = false;
> +	}
>  }
>  
>  static void perf_db_event(void *ctx, int vec)
> @@ -547,18 +552,6 @@ out:
>  				      msecs_to_jiffies(PERF_LINK_DOW
> N_TIMEOUT));
>  }
>  
> -static void perf_link_cleanup(struct work_struct *work)
> -{
> -	struct perf_ctx *perf = container_of(work,
> -					     struct perf_ctx,
> -					     link_cleanup);
> -
> -	dev_dbg(&perf->ntb->pdev->dev, "%s called\n", __func__);
> -
> -	if (!perf->link_is_up)
> -		cancel_delayed_work_sync(&perf->link_work);
> -}
> -
>  static int perf_setup_mw(struct ntb_dev *ntb, struct perf_ctx *perf)
>  {
>  	struct perf_mw *mw;
> @@ -787,7 +780,6 @@ static int perf_probe(struct ntb_client *client,
> struct ntb_dev *ntb)
>  	perf_setup_mw(ntb, perf);
>  	init_waitqueue_head(&perf->link_wq);
>  	INIT_DELAYED_WORK(&perf->link_work, perf_link_work);
> -	INIT_WORK(&perf->link_cleanup, perf_link_cleanup);
>  
>  	rc = ntb_set_ctx(ntb, perf, &perf_ops);
>  	if (rc)
> @@ -807,7 +799,6 @@ static int perf_probe(struct ntb_client *client,
> struct ntb_dev *ntb)
>  
>  err_ctx:
>  	cancel_delayed_work_sync(&perf->link_work);
> -	cancel_work_sync(&perf->link_cleanup);
>  	kfree(perf);
>  err_perf:
>  	return rc;
> @@ -823,7 +814,6 @@ static void perf_remove(struct ntb_client
> *client, struct ntb_dev *ntb)
>  	mutex_lock(&perf->run_mutex);
>  
>  	cancel_delayed_work_sync(&perf->link_work);
> -	cancel_work_sync(&perf->link_cleanup);
>  
>  	ntb_clear_ctx(ntb);
>  	ntb_link_disable(ntb);
> -- 
> 2.1.4
>