netdev - Re: [PATCH net-next V2 3/4] net/mlx5e: Add HW timestamping (TS) support

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Message-ID: <20151221091509.GA2297@localhost.localdomain>
Date:	Mon, 21 Dec 2015 10:15:09 +0100
From:	Richard Cochran <richardcochran@...il.com>
To:	Saeed Mahameed <saeedm@...lanox.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Eran Ben Elisha <eranbe@...lanox.com>,
	Tal Alon <talal@...lanox.com>,
	Majd Dibbiny <majd@...lanox.com>,
	Achiad Shochat <achiad@...lanox.com>, saeedm@....mellanox.co.il
Subject: Re: [PATCH net-next V2 3/4] net/mlx5e: Add HW timestamping (TS)
 support

On Sun, Dec 20, 2015 at 11:46:30PM +0200, Saeed Mahameed wrote:
> +/* Should run once every mlx5e_tstamp->overflow_period */
> +static void mlx5e_timestamp_overflow(struct work_struct *work)
> +{
> +	struct delayed_work *dwork = to_delayed_work(work);
> +	struct mlx5e_tstamp *tstamp = container_of(dwork, struct mlx5e_tstamp, overflow_work);
> +	unsigned long flags;
> +
> +	write_lock_irqsave(&tstamp->lock, flags);
> +	timecounter_read(&tstamp->clock);
> +	if (tstamp->overflow_period)
> +		schedule_delayed_work(&tstamp->overflow_work, tstamp->overflow_period);

You don't need this test, and the call to schedule_delayed_work can be
outside of the lock.

> +	write_unlock_irqrestore(&tstamp->lock, flags);
> +}

> +void mlx5e_timestamp_cleanup(struct mlx5e_priv *priv)
> +{
> +	struct mlx5e_tstamp *tstamp = &priv->tstamp;
> +
> +	if (!MLX5_CAP_GEN(priv->mdev, device_frequency_khz))
> +		return;
> +
> +	write_lock(&tstamp->lock);
> +	tstamp->overflow_period = 0; /* Signal overflow_check to stop */
> +	write_unlock(&tstamp->lock);

This is unnecessary because

> +
> +	cancel_delayed_work_sync(&tstamp->overflow_work);

this will block until the work is cancelled.

> +}

Thanks,
Richard


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