Re: [PATCH net-next v2] net: skb: prevent the split of kfree_skb_reason() by gcc

From: kernel test robot
Date: Fri Aug 12 2022 - 22:09:15 EST


Hi,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on net-next/master]

url: https://github.com/intel-lab-lkp/linux/commits/menglong8-dong-gmail-com/net-skb-prevent-the-split-of-kfree_skb_reason-by-gcc/20220812-105214
base: https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git 7ebfc85e2cd7b08f518b526173e9a33b56b3913b
config: i386-randconfig-a002 (https://download.01.org/0day-ci/archive/20220813/202208131003.M7FBGBna-lkp@xxxxxxxxx/config)
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 5f1c7e2cc5a3c07cbc2412e851a7283c1841f520)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/intel-lab-lkp/linux/commit/ec98116fd4b985103e65c71d47f9390fee025cb9
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review menglong8-dong-gmail-com/net-skb-prevent-the-split-of-kfree_skb_reason-by-gcc/20220812-105214
git checkout ec98116fd4b985103e65c71d47f9390fee025cb9
# save the config file
mkdir build_dir && cp config build_dir/.config
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash net/core/

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All warnings (new ones prefixed by >>):

>> net/core/skbuff.c:780:6: warning: unknown attribute '__optimize__' ignored [-Wunknown-attributes]
void __nofnsplit
^~~~~~~~~~~
include/linux/compiler_attributes.h:273:56: note: expanded from macro '__nofnsplit'
#define __nofnsplit __attribute__((__optimize__("O1")))
^~~~~~~~~~~~~~~~~~
1 warning generated.


vim +/__optimize__ +780 net/core/skbuff.c

770
771 /**
772 * kfree_skb_reason - free an sk_buff with special reason
773 * @skb: buffer to free
774 * @reason: reason why this skb is dropped
775 *
776 * Drop a reference to the buffer and free it if the usage count has
777 * hit zero. Meanwhile, pass the drop reason to 'kfree_skb'
778 * tracepoint.
779 */
> 780 void __nofnsplit
781 kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason)
782 {
783 if (!skb_unref(skb))
784 return;
785
786 DEBUG_NET_WARN_ON_ONCE(reason <= 0 || reason >= SKB_DROP_REASON_MAX);
787
788 trace_kfree_skb(skb, __builtin_return_address(0), reason);
789 __kfree_skb(skb);
790 }
791 EXPORT_SYMBOL(kfree_skb_reason);
792

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