netdev - Re: [PATCH 1/1] tcp: Honor the eor bit in tcp_mtu

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Date:   Wed, 7 Feb 2018 05:29:42 +0800
From:   kbuild test robot <lkp@...el.com>
To:     Ilya Lesokhin <ilyal@...lanox.com>
Cc:     kbuild-all@...org, netdev@...r.kernel.org, kafai@...com,
        borisp@...lanox.com, Ilya Lesokhin <ilyal@...lanox.com>
Subject: Re: [PATCH 1/1] tcp: Honor the eor bit in tcp_mtu_probe

Hi Ilya,

I love your patch! Perhaps something to improve:

[auto build test WARNING on net/master]
[also build test WARNING on v4.15 next-20180206]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Ilya-Lesokhin/tcp-Honor-the-eor-bit-in-tcp_mtu_probe/20180207-045040
config: i386-randconfig-x007-201805 (attached as .config)
compiler: gcc-7 (Debian 7.2.0-12) 7.2.1 20171025
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   In file included from include/linux/tcp.h:21:0,
                    from include/net/tcp.h:24,
                    from net//ipv4/tcp_output.c:39:
   net//ipv4/tcp_output.c: In function 'tcp_write_xmit':
>> include/linux/skbuff.h:3196:12: warning: 'skb' may be used uninitialized in this function [-Wmaybe-uninitialized]
      for (tmp = skb->next;      \
               ^
   net//ipv4/tcp_output.c:2043:18: note: 'skb' was declared here
     struct sk_buff *skb, *nskb, *next;
                     ^~~
--
   In file included from include/linux/tcp.h:21:0,
                    from include/net/tcp.h:24,
                    from net/ipv4/tcp_output.c:39:
   net/ipv4/tcp_output.c: In function 'tcp_write_xmit':
>> include/linux/skbuff.h:3196:12: warning: 'skb' may be used uninitialized in this function [-Wmaybe-uninitialized]
      for (tmp = skb->next;      \
               ^
   net/ipv4/tcp_output.c:2043:18: note: 'skb' was declared here
     struct sk_buff *skb, *nskb, *next;
                     ^~~

vim +/skb +3196 include/linux/skbuff.h

18a4c0eab Eric Dumazet    2017-10-05  3168  
^1da177e4 Linus Torvalds  2005-04-16  3169  #define skb_queue_walk(queue, skb) \
^1da177e4 Linus Torvalds  2005-04-16  3170  		for (skb = (queue)->next;					\
a1e4891fd Linus Torvalds  2011-05-22  3171  		     skb != (struct sk_buff *)(queue);				\
^1da177e4 Linus Torvalds  2005-04-16  3172  		     skb = skb->next)
^1da177e4 Linus Torvalds  2005-04-16  3173  
46f8914e5 James Chapman   2007-04-30  3174  #define skb_queue_walk_safe(queue, skb, tmp)					\
46f8914e5 James Chapman   2007-04-30  3175  		for (skb = (queue)->next, tmp = skb->next;			\
46f8914e5 James Chapman   2007-04-30  3176  		     skb != (struct sk_buff *)(queue);				\
46f8914e5 James Chapman   2007-04-30  3177  		     skb = tmp, tmp = skb->next)
46f8914e5 James Chapman   2007-04-30  3178  
1164f52a2 David S. Miller 2008-09-23  3179  #define skb_queue_walk_from(queue, skb)						\
a1e4891fd Linus Torvalds  2011-05-22  3180  		for (; skb != (struct sk_buff *)(queue);			\
1164f52a2 David S. Miller 2008-09-23  3181  		     skb = skb->next)
1164f52a2 David S. Miller 2008-09-23  3182  
18a4c0eab Eric Dumazet    2017-10-05  3183  #define skb_rbtree_walk(skb, root)						\
18a4c0eab Eric Dumazet    2017-10-05  3184  		for (skb = skb_rb_first(root); skb != NULL;			\
18a4c0eab Eric Dumazet    2017-10-05  3185  		     skb = skb_rb_next(skb))
18a4c0eab Eric Dumazet    2017-10-05  3186  
18a4c0eab Eric Dumazet    2017-10-05  3187  #define skb_rbtree_walk_from(skb)						\
18a4c0eab Eric Dumazet    2017-10-05  3188  		for (; skb != NULL;						\
18a4c0eab Eric Dumazet    2017-10-05  3189  		     skb = skb_rb_next(skb))
18a4c0eab Eric Dumazet    2017-10-05  3190  
18a4c0eab Eric Dumazet    2017-10-05  3191  #define skb_rbtree_walk_from_safe(skb, tmp)					\
18a4c0eab Eric Dumazet    2017-10-05  3192  		for (; tmp = skb ? skb_rb_next(skb) : NULL, (skb != NULL);	\
18a4c0eab Eric Dumazet    2017-10-05  3193  		     skb = tmp)
18a4c0eab Eric Dumazet    2017-10-05  3194  
1164f52a2 David S. Miller 2008-09-23  3195  #define skb_queue_walk_from_safe(queue, skb, tmp)				\
1164f52a2 David S. Miller 2008-09-23 @3196  		for (tmp = skb->next;						\
1164f52a2 David S. Miller 2008-09-23  3197  		     skb != (struct sk_buff *)(queue);				\
1164f52a2 David S. Miller 2008-09-23  3198  		     skb = tmp, tmp = skb->next)
1164f52a2 David S. Miller 2008-09-23  3199  

:::::: The code at line 3196 was first introduced by commit
:::::: 1164f52a244204830c7625b3c22812781996d7b4 net: Add skb_queue_walk_from() and skb_queue_walk_from_safe().

:::::: TO: David S. Miller <davem@...emloft.net>
:::::: CC: David S. Miller <davem@...emloft.net>

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