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Message-ID: <9c8018ba-4808-73eb-a6c2-13c194097d4b@ya.ru>
Date: Sat, 14 Jan 2023 12:30:22 +0300
From: Kirill Tkhai <tkhai@...ru>
To: kernel test robot <lkp@...el.com>, davem@...emloft.net,
edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
kuniyu@...zon.com, netdev@...r.kernel.org
Cc: llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev
Subject: Re: [PATCH net-next] unix: Improve locking scheme in
unix_show_fdinfo()
On 14.01.2023 08:30, kernel test robot wrote:
> Hi Kirill,
>
> 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/Kirill-Tkhai/unix-Improve-locking-scheme-in-unix_show_fdinfo/20230114-082118
> patch link: https://lore.kernel.org/r/9d951e81-2051-5b67-a394-2cb819e5bf57%40ya.ru
> patch subject: [PATCH net-next] unix: Improve locking scheme in unix_show_fdinfo()
> config: x86_64-rhel-8.3-rust
> compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
> 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/1c3b5ffa3da1bc362d28489fc860432b09e8a451
> git remote add linux-review https://github.com/intel-lab-lkp/linux
> git fetch --no-tags linux-review Kirill-Tkhai/unix-Improve-locking-scheme-in-unix_show_fdinfo/20230114-082118
> git checkout 1c3b5ffa3da1bc362d28489fc860432b09e8a451
> # save the config file
> mkdir build_dir && cp config build_dir/.config
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 olddefconfig
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash net/unix/
>
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@...el.com>
>
> All warnings (new ones prefixed by >>):
>
>>> net/unix/af_unix.c:824:12: warning: variable 'nr_fds' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
> else if (s_state == TCP_LISTEN)
> ^~~~~~~~~~~~~~~~~~~~~
> net/unix/af_unix.c:827:34: note: uninitialized use occurs here
> seq_printf(m, "scm_fds: %u\n", nr_fds);
> ^~~~~~
> net/unix/af_unix.c:824:8: note: remove the 'if' if its condition is always true
> else if (s_state == TCP_LISTEN)
> ^~~~~~~~~~~~~~~~~~~~~~~~~~
> net/unix/af_unix.c:812:12: note: initialize the variable 'nr_fds' to silence this warning
> int nr_fds;
> ^
> = 0
Strange, my gcc didn't warn me... I will send v2.
> 1 warning generated.
>
>
> vim +824 net/unix/af_unix.c
>
> 806
> 807 static void unix_show_fdinfo(struct seq_file *m, struct socket *sock)
> 808 {
> 809 struct sock *sk = sock->sk;
> 810 unsigned char s_state;
> 811 struct unix_sock *u;
> 812 int nr_fds;
> 813
> 814 if (sk) {
> 815 s_state = READ_ONCE(sk->sk_state);
> 816 u = unix_sk(sk);
> 817
> 818 /* SOCK_STREAM and SOCK_SEQPACKET sockets never change their
> 819 * sk_state after switching to TCP_ESTABLISHED or TCP_LISTEN.
> 820 * SOCK_DGRAM is ordinary. So, no lock is needed.
> 821 */
> 822 if (sock->type == SOCK_DGRAM || s_state == TCP_ESTABLISHED)
> 823 nr_fds = atomic_read(&u->scm_stat.nr_fds);
> > 824 else if (s_state == TCP_LISTEN)
> 825 nr_fds = unix_count_nr_fds(sk);
> 826
> 827 seq_printf(m, "scm_fds: %u\n", nr_fds);
> 828 }
> 829 }
> 830 #else
> 831 #define unix_show_fdinfo NULL
> 832 #endif
> 833
>
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