Re: [PATCH] tty: n_tty: annotate lockless read of ldata->icanon in input_available_p()

[kernel test robot <lkp@intel.com>]

Hi Ziyu,

kernel test robot noticed the following build errors:

[auto build test ERROR on tty/tty-testing]
[also build test ERROR on tty/tty-next tty/tty-linus linus/master v6.16-rc1 next-20260316]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Ziyu-Zhang/tty-n_tty-annotate-lockless-read-of-ldata-icanon-in-input_available_p/20260316-224221
base:   https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git tty-testing
patch link:    https://lore.kernel.org/r/20260316132827.17855-1-ziyuzhang201%40gmail.com
patch subject: [PATCH] tty: n_tty: annotate lockless read of ldata->icanon in input_available_p()
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20260316/202603162328.vY9JOJWL-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260316/202603162328.vY9JOJWL-lkp@intel.com/reproduce)

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/202603162328.vY9JOJWL-lkp@intel.com/

All errors (new ones prefixed by >>):

>> drivers/tty/n_tty.c:1913:6: error: cannot pass bit-field as __auto_type initializer in C
    1913 |         if (data_race(ldata->icanon) && !L_EXTPROC(tty))
         |             ^
   include/linux/compiler.h:194:13: note: expanded from macro 'data_race'
     194 |         auto __v = (expr);                                              \
         |                    ^
   1 error generated.


vim +1913 drivers/tty/n_tty.c

  1906	
  1907	static inline int input_available_p(const struct tty_struct *tty, int poll)
  1908	{
  1909		const struct n_tty_data *ldata = tty->disc_data;
  1910		int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
  1911	
  1912		/* data_race: benign race, poll readiness is best-effort */
> 1913		if (data_race(ldata->icanon) && !L_EXTPROC(tty))
  1914			return ldata->canon_head != ldata->read_tail;
  1915		else
  1916			return ldata->commit_head - ldata->read_tail >= amt;
  1917	}
  1918	

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