Message ID | 20220812025015.316609-1-imagedong@tencent.com (mailing list archive) |
---|---|
State | Superseded |
Delegated to: | Netdev Maintainers |
Headers | show |
Series | [net-next,v2] net: skb: prevent the split of kfree_skb_reason() by gcc | expand |
On Fri, Aug 12, 2022 at 4:50 AM <menglong8.dong@gmail.com> wrote: > > #define __noreturn __attribute__((__noreturn__)) > > +#define __nofnsplit __attribute__((__optimize__("O1"))) This is still in the wrong place... Also, from what the bot says, Clang does not support it. I took a look, and that seems to be the case. ICC doesn't, either. Thus you would need to guard it and also add the docs as needed, like the other attributes. (Not saying that solving the issue with the attribute is a good idea, but if you really wanted to add one, it should be done properly) Cheers, Miguel
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@intel.com/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@intel.com> 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
Hello, On Fri, Aug 12, 2022 at 4:50 PM Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> wrote: > > On Fri, Aug 12, 2022 at 4:50 AM <menglong8.dong@gmail.com> wrote: > > > > #define __noreturn __attribute__((__noreturn__)) > > > > +#define __nofnsplit __attribute__((__optimize__("O1"))) > > This is still in the wrong place... > > Also, from what the bot says, Clang does not support it. I took a > look, and that seems to be the case. ICC doesn't, either. Thus you > would need to guard it and also add the docs as needed, like the other > attributes. > > (Not saying that solving the issue with the attribute is a good idea, > but if you really wanted to add one, it should be done properly) > I have dug it deeper, and found that this function-split optimization is only used by GCC. Therefore, I think I need only to consider it for GCC. I'll send a V3, thanks~ Menglong Dong > Cheers, > Miguel
diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h index 445e80517cab..b910b5775fc7 100644 --- a/include/linux/compiler_attributes.h +++ b/include/linux/compiler_attributes.h @@ -270,6 +270,8 @@ */ #define __noreturn __attribute__((__noreturn__)) +#define __nofnsplit __attribute__((__optimize__("O1"))) + /* * Optional: not supported by gcc. * Optional: not supported by icc. diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 974bbbbe7138..ff9ccbc032b9 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -777,7 +777,8 @@ EXPORT_SYMBOL(__kfree_skb); * hit zero. Meanwhile, pass the drop reason to 'kfree_skb' * tracepoint. */ -void kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason) +void __nofnsplit +kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason) { if (!skb_unref(skb)) return;