linux-kernel - Re: [PATCH 3.9-stable] NTB: memcpy lockup workaround

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Date:	Sat, 18 May 2013 07:48:49 -0700
From:	Jon Mason <jon.mason@...el.com>
To:	Jonghwan Choi <jhbird.choi@...il.com>
Cc:	stable@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jonghwan Choi <jhbird.choi@...sung.com>
Subject: Re: [PATCH 3.9-stable] NTB: memcpy lockup workaround

On Sat, May 18, 2013 at 11:52:17AM +0900, Jonghwan Choi wrote:
> From: Jon Mason <jon.mason@...el.com>
> 
> This patch looks like it should be in the 3.9-stable tree, should we apply
> it?

Yes, thanks.

> 
> ------------------
> 
> From: "Jon Mason <jon.mason@...el.com>"
> 
> commit c336acd3331dcc191a97dbc66a557d47741657c7 upstream
> 
> The system will appear to lockup for long periods of time due to the NTB
> driver spending too much time in memcpy.  Avoid this by reducing the
> number of packets that can be serviced on a given interrupt.
> 
> Cc: <stable@...r.kernel.org> # 3.9.x: ad3e2751: ntb: off by one
> Cc: <stable@...r.kernel.org> # 3.9.x: cc0f868d: NTB: fix pointer math
> Cc: <stable@...r.kernel.org> # 3.9.x: 113fc505: NTB: Handle 64bit BAR
> Cc: <stable@...r.kernel.org> # 3.9.x: b77b2637: NTB: Link toggle memory
> Cc: <stable@...r.kernel.org> # 3.9.x: 90f9e934: NTB: reset tx_index on
> Cc: <stable@...r.kernel.org> # 3.9.x: c9d534c8: NTB: Correctly handle receive
> Signed-off-by: Jon Mason <jon.mason@...el.com>
> Signed-off-by: Jonghwan Choi <jhbird.choi@...sung.com>
> ---
>  drivers/ntb/ntb_transport.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c
> index a288a26..0f66daa 100644
> --- a/drivers/ntb/ntb_transport.c
> +++ b/drivers/ntb/ntb_transport.c
> @@ -1034,11 +1034,16 @@ out:
>  static void ntb_transport_rx(unsigned long data)
>  {
>  	struct ntb_transport_qp *qp = (struct ntb_transport_qp *)data;
> -	int rc;
> +	int rc, i;
>  
> -	do {
> +	/* Limit the number of packets processed in a single interrupt to
> +	 * provide fairness to others
> +	 */
> +	for (i = 0; i < qp->rx_max_entry; i++) {
>  		rc = ntb_process_rxc(qp);
> -	} while (!rc);
> +		if (rc)
> +			break;
> +	}
>  }
>  
>  static void ntb_transport_rxc_db(void *data, int db_num)
> -- 
> 1.8.1.2
> 
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