Re: [PATCH v2 1/2] net: nps_enet: Sync access to packet sent flag

From	David Miller <davem@davemloft.net>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2 1/2] net: nps_enet: Sync access to packet sent flag
Date	2016-04-28 23:20 +0200
Message-ID	<rt1vR-2uF-29@gated-at.bofh.it> (permalink)
References	<rsyau-26F-7@gated-at.bofh.it> <rsyau-26F-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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From: Elad Kanfi <eladkan@mellanox.com>
Date: Wed, 27 Apr 2016 16:18:29 +0300

> From: Elad Kanfi <eladkan@mellanox.com>
> 
> Below is a description of a possible problematic
> sequence. CPU-A is sending a frame and CPU-B handles
> the interrupt that indicates the frame was sent. CPU-B
> reads an invalid value of tx_packet_sent.
> 
> 	CPU-A				CPU-B
> 	-----				-----
> 	nps_enet_send_frame
> 	.
> 	.
> 	tx_packet_sent = true
> 	order HW to start tx
> 	.
> 	.
> 	HW complete tx
> 			    ------> 	get tx complete interrupt
> 					.
> 					.
> 					if(tx_packet_sent == true)
> 
> 	end memory transaction
> 	(tx_packet_sent actually
> 	 written)
> 
> Problem solution:
> 
> Add a memory barrier after setting tx_packet_sent,
> in order to make sure that it is written before
> the packet is sent.
> 
> Signed-off-by: Elad Kanfi <eladkan@mellanox.com>
> 
> Acked-by: Noam Camus <noamca@mellanox.com>

Please address the feedback about memory barrier pairing.

Also, for both patches, do not put empty lines between the various
tags at the end of the commit message.  They should all be together
in one continuous group.

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Re: [PATCH v2 1/2] net: nps_enet: Sync access to packet sent flag David Miller <davem@davemloft.net> - 2016-04-28 23:20 +0200
  RE: [PATCH v2 1/2] net: nps_enet: Sync access to packet sent flag Elad Kanfi <eladkan@mellanox.com> - 2016-05-02 13:00 +0200
    Re: [PATCH v2 1/2] net: nps_enet: Sync access to packet sent flag Lino Sanfilippo <lsanfil@marvell.com> - 2016-05-02 13:20 +0200
      RE: [PATCH v2 1/2] net: nps_enet: Sync access to packet sent flag Elad Kanfi <eladkan@mellanox.com> - 2016-05-08 16:00 +0200
        Re: [PATCH v2 1/2] net: nps_enet: Sync access to packet sent flag Lino Sanfilippo <LinoSanfilippo@gmx.de> - 2016-05-10 20:40 +0200

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