netdev - Re: [PATCH 02/11] bnx2: Call dev_kfree_skby_any instead of dev_kfree

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Date:	Mon, 10 Mar 2014 21:10:26 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	xiyou.wangcong@...il.com, mpm@...enic.com, satyam.sharma@...il.com
Subject: Re: [PATCH 02/11] bnx2: Call dev_kfree_skby_any instead of dev_kfree_skb.

Eric Dumazet <eric.dumazet@...il.com> writes:

> On Mon, 2014-03-10 at 20:18 -0700, Eric W. Biederman wrote:
>> Replace dev_kfree_skb with dev_kfree_skb_any in functions that can
>> be called in hard irq and other contexts.
>> 
>> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
>> ---
>>  drivers/net/ethernet/broadcom/bnx2.c |   10 +++++-----
>>  1 files changed, 5 insertions(+), 5 deletions(-)
>> 
>> diff --git a/drivers/net/ethernet/broadcom/bnx2.c b/drivers/net/ethernet/broadcom/bnx2.c
>> index ca6b36220d94..c94735de808d 100644
>> --- a/drivers/net/ethernet/broadcom/bnx2.c
>> +++ b/drivers/net/ethernet/broadcom/bnx2.c
>> @@ -2885,7 +2885,7 @@ bnx2_tx_int(struct bnx2 *bp, struct bnx2_napi *bnapi, int budget)
>>  		sw_cons = BNX2_NEXT_TX_BD(sw_cons);
>>  
>>  		tx_bytes += skb->len;
>> -		dev_kfree_skb(skb);
>> +		dev_kfree_skb_any(skb);
>
> This looks like a dev_consume_skb_any() candidate ?

That seems reasonable.  I am focusing on one dimension at a time.

> Anyway, why can this be called from hard irq ?

netpoll_poll_dev
   bnx2_poll
     bnx2_poll_work
       bnx2_tx_int

> I'll stop my review here, it seems either me or you are confused/tired.

I did my best to verify the code paths I am changing actually exist.  I
think I even have a stack backtrace from skb_release_head_state around
somewhere.  Transmitted packets frequently have dst cache entries,
conntrack entries, and destructores which make them actually problematic
to free in hard irq context.

Eric

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