netdev - Re: [PATCH net 1/1] via-velocity: fix netif_receive

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Message-Id: <20131128.184529.1997166326512828518.davem@davemloft.net>
Date:	Thu, 28 Nov 2013 18:45:29 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	romieu@...zoreil.com
Cc:	netdev@...r.kernel.org, aaschmidt1@...il.com, michele@...syn.org,
	jamie@...ible.transient.net, Julia.Lawall@...6.fr
Subject: Re: [PATCH net 1/1] via-velocity: fix netif_receive_skb use in irq
 disabled section.

From: Francois Romieu <romieu@...zoreil.com>
Date: Tue, 26 Nov 2013 00:40:58 +0100

> 2fdac010bdcf10a30711b6924612dfc40daf19b8 ("via-velocity.c: update napi
> implementation") overlooked an irq disabling spinlock when the Rx part
> of the NAPI poll handler was converted from netif_rx to netif_receive_skb.
> 
> NAPI Rx processing can be taken out of the locked section with a pair of
> napi_{disable / enable} since it only races with the MTU change function.
> 
> An heavier rework of the NAPI locking would be able to perform NAPI Tx
> before Rx where I simply removed one of velocity_tx_srv calls.
> 
> References: https://bugzilla.redhat.com/show_bug.cgi?id=1022733
> Fixes: 2fdac010bdcf (via-velocity.c: update napi implementation)
> Signed-off-by: Francois Romieu <romieu@...zoreil.com>
> Tested-by: Alex A. Schmidt <aaschmidt1@...il.com>

Applied and queued up for -stable, thanks.

Just a note that we usually recommend to people to do TX processing
before RX in NAPI, because the TX work can liberate packets and make
them available to RX reclaim.  But that would be quite hard with the
approach you took to fix this bug simply.
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