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From: Leonardo Bras <leobras@redhat.com>
To: kernel test robot <lkp@intel.com>
Cc: Leonardo Bras <leobras@redhat.com>,
	Will Deacon <will@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Boqun Feng <boqun.feng@gmail.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Guo Ren <guoren@kernel.org>,
	Andrea Parri <parri.andrea@gmail.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Ingo Molnar <mingo@kernel.org>,
	Andrzej Hajda <andrzej.hajda@intel.com>,
	oe-kbuild-all@lists.linux.dev,
	linux-kernel@vger.kernel.org,
	linux-riscv@lists.infradead.org
Subject: Re: [PATCH v1 1/5] riscv/cmpxchg: Deduplicate xchg() asm functions
Date: Tue, 16 Jan 2024 16:27:07 -0300
Message-ID: <ZabYi5NoTiXJ4Hf2@LeoBras>
In-Reply-To: <202401131438.f8SELM0W-lkp@intel.com>
References: <20240103163203.72768-3-leobras@redhat.com> <202401131438.f8SELM0W-lkp@intel.com>
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On Sat, Jan 13, 2024 at 02:54:17PM +0800, kernel test robot wrote:
> Hi Leonardo,
> 
> kernel test robot noticed the following build warnings:
> 
> [auto build test WARNING on 610a9b8f49fbcf1100716370d3b5f6f884a2835a]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Leonardo-Bras/riscv-cmpxchg-Deduplicate-xchg-asm-functions/20240104-003501

Cloned this repo

> base:   610a9b8f49fbcf1100716370d3b5f6f884a2835a
> patch link:    https://lore.kernel.org/r/20240103163203.72768-3-leobras%40redhat.com
> patch subject: [PATCH v1 1/5] riscv/cmpxchg: Deduplicate xchg() asm functions
> config: riscv-randconfig-r111-20240112 (https://download.01.org/0day-ci/archive/20240113/202401131438.f8SELM0W-lkp@intel.com/config)
> compiler: clang version 18.0.0git (https://github.com/llvm/llvm-project 9bde5becb44ea071f5e1fa1f5d4071dc8788b18c)
> reproduce: (https://download.01.org/0day-ci/archive/20240113/202401131438.f8SELM0W-lkp@intel.com/reproduce)

And followed those instructions, while using sparse v0.6.4-52-g1cf3d98c.

> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202401131438.f8SELM0W-lkp@intel.com/
> 
> sparse warnings: (new ones prefixed by >>)
> >> net/ipv4/tcp_cong.c:300:24: sparse: sparse: incorrect type in initializer (different address spaces) @@     expected struct tcp_congestion_ops const [noderef] __rcu *__new @@     got struct tcp_congestion_ops *[assigned] ca @@
>    net/ipv4/tcp_cong.c:300:24: sparse:     expected struct tcp_congestion_ops const [noderef] __rcu *__new
>    net/ipv4/tcp_cong.c:300:24: sparse:     got struct tcp_congestion_ops *[assigned] ca
>    net/ipv4/tcp_cong.c:300:22: sparse: sparse: incorrect type in assignment (different address spaces) @@     expected struct tcp_congestion_ops const *prev @@     got struct tcp_congestion_ops const [noderef] __rcu * @@
>    net/ipv4/tcp_cong.c:300:22: sparse:     expected struct tcp_congestion_ops const *prev
>    net/ipv4/tcp_cong.c:300:22: sparse:     got struct tcp_congestion_ops const [noderef] __rcu *
>    net/ipv4/tcp_cong.c: note: in included file (through include/linux/module.h):
>    include/linux/list.h:83:21: sparse: sparse: self-comparison always evaluates to true
>    include/linux/list.h:83:21: sparse: sparse: self-comparison always evaluates to true
> 
> vim +300 net/ipv4/tcp_cong.c
> 
> 317a76f9a44b43 Stephen Hemminger 2005-06-23  281  
> 317a76f9a44b43 Stephen Hemminger 2005-06-23  282  /* Used by sysctl to change default congestion control */
> 6670e152447732 Stephen Hemminger 2017-11-14  283  int tcp_set_default_congestion_control(struct net *net, const char *name)
> 317a76f9a44b43 Stephen Hemminger 2005-06-23  284  {
> 317a76f9a44b43 Stephen Hemminger 2005-06-23  285  	struct tcp_congestion_ops *ca;
> 6670e152447732 Stephen Hemminger 2017-11-14  286  	const struct tcp_congestion_ops *prev;
> 6670e152447732 Stephen Hemminger 2017-11-14  287  	int ret;
> 317a76f9a44b43 Stephen Hemminger 2005-06-23  288  
> 6670e152447732 Stephen Hemminger 2017-11-14  289  	rcu_read_lock();
> 6670e152447732 Stephen Hemminger 2017-11-14  290  	ca = tcp_ca_find_autoload(net, name);
> 6670e152447732 Stephen Hemminger 2017-11-14  291  	if (!ca) {
> 6670e152447732 Stephen Hemminger 2017-11-14  292  		ret = -ENOENT;
> 0baf26b0fcd74b Martin KaFai Lau  2020-01-08  293  	} else if (!bpf_try_module_get(ca, ca->owner)) {
> 6670e152447732 Stephen Hemminger 2017-11-14  294  		ret = -EBUSY;
> 8d432592f30fcc Jonathon Reinhart 2021-05-01  295  	} else if (!net_eq(net, &init_net) &&
> 8d432592f30fcc Jonathon Reinhart 2021-05-01  296  			!(ca->flags & TCP_CONG_NON_RESTRICTED)) {
> 8d432592f30fcc Jonathon Reinhart 2021-05-01  297  		/* Only init netns can set default to a restricted algorithm */
> 8d432592f30fcc Jonathon Reinhart 2021-05-01  298  		ret = -EPERM;
> 6670e152447732 Stephen Hemminger 2017-11-14  299  	} else {
> 6670e152447732 Stephen Hemminger 2017-11-14 @300  		prev = xchg(&net->ipv4.tcp_congestion_control, ca);
> 6670e152447732 Stephen Hemminger 2017-11-14  301  		if (prev)
> 0baf26b0fcd74b Martin KaFai Lau  2020-01-08  302  			bpf_module_put(prev, prev->owner);
> 317a76f9a44b43 Stephen Hemminger 2005-06-23  303  
> 6670e152447732 Stephen Hemminger 2017-11-14  304  		ca->flags |= TCP_CONG_NON_RESTRICTED;
> 317a76f9a44b43 Stephen Hemminger 2005-06-23  305  		ret = 0;
> 317a76f9a44b43 Stephen Hemminger 2005-06-23  306  	}
> 6670e152447732 Stephen Hemminger 2017-11-14  307  	rcu_read_unlock();
> 317a76f9a44b43 Stephen Hemminger 2005-06-23  308  
> 317a76f9a44b43 Stephen Hemminger 2005-06-23  309  	return ret;
> 317a76f9a44b43 Stephen Hemminger 2005-06-23  310  }
> 317a76f9a44b43 Stephen Hemminger 2005-06-23  311  
> 
> -- 
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki
> 

I did some testing using the instructions above on above file, and patch 
1/5 haven't introduced anything new.


Command for gathering sparse warnings:
COMPILER_INSTALL_PATH=$HOME/0day ~/lkp-tests/kbuild/make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=riscv SHELL=/bin/bash net/ipv4/tcp_cong.o 2> sparse

I ran this for the commit mentioned in the reproduction instructions 
(7931dc023 : riscv/cmpxchg: Deduplicate xchg() asm functions ) and for it's 
parent (610a9b8f49 : Linux 6.7-rc8). The diff -u on the output was:

# diff -u sparse_vanilla sparse_p1_5    
--- sparse_vanilla      2024-01-16 14:16:36.217965076 -0500              
+++ sparse_p1_5 2024-01-16 14:15:29.942712160 -0500                      
@@ -1,5 +1,5 @@                                                          
 ../net/ipv4/tcp_cong.c:300:24: sparse: warning: incorrect type in initializer (different address spaces)
-../net/ipv4/tcp_cong.c:300:24: sparse:    expected struct tcp_congestion_ops const [noderef] __rcu *_x_
+../net/ipv4/tcp_cong.c:300:24: sparse:    expected struct tcp_congestion_ops const [noderef] __rcu *__new
 ../net/ipv4/tcp_cong.c:300:24: sparse:    got struct tcp_congestion_ops *[assigned] ca
 ../net/ipv4/tcp_cong.c:300:22: sparse: warning: incorrect type in assignment (different address spaces)
 ../net/ipv4/tcp_cong.c:300:22: sparse:    expected struct tcp_congestion_ops const *prev

So I did not introduce anything new, as per sparse v0.6.4-52-g1cf3d98c .

I noticed the output is slightly different, and that in the reproduction 
steps this used:
# sparse version: v0.6.4-52-g1cf3d98c-dirty

Since there is no indicator on what the -dirty stands for, it's hard for me 
to get the same reproduction, but as far as I could test there is not 
any new error. 

Thanks!
Leo