Re: [PATCH v2 1/3] tracing: Have futex syscall trace event show specific user data

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

Hi Steven,

kernel test robot noticed the following build warnings:

[auto build test WARNING on tip/locking/core]
[also build test WARNING on trace/for-next akpm-mm/mm-everything linus/master v7.0-rc3 next-20260310]
[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/Steven-Rostedt/tracing-Have-futex-syscall-trace-event-show-specific-user-data/20260311-041422
base:   tip/locking/core
patch link:    https://lore.kernel.org/r/20260310201036.542627924%40kernel.org
patch subject: [PATCH v2 1/3] tracing: Have futex syscall trace event show specific user data
config: arc-randconfig-001-20260311 (https://download.01.org/0day-ci/archive/20260311/202603111911.zAWpiGlz-lkp@intel.com/config)
compiler: arc-linux-gcc (GCC) 14.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260311/202603111911.zAWpiGlz-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/202603111911.zAWpiGlz-lkp@intel.com/

All warnings (new ones prefixed by >>):

   kernel/trace/trace_syscalls.c: In function 'syscall_get_futex':
>> kernel/trace/trace_syscalls.c:807:15: warning: variable 'buf' set but not used [-Wunused-but-set-variable]
     807 |         char *buf;
         |               ^~~


vim +/buf +807 kernel/trace/trace_syscalls.c

   801	
   802	static int
   803	syscall_get_futex(unsigned long *args, char **buffer, int *size, int buf_size)
   804	{
   805		struct syscall_user_buffer *sbuf;
   806		const char __user *ptr;
 > 807		char *buf;
   808	
   809		/* buf_size of zero means user doesn't want user space read */
   810		if (!buf_size)
   811			return -1;
   812	
   813		/* If the syscall_buffer is NULL, tracing is being shutdown */
   814		sbuf = READ_ONCE(syscall_buffer);
   815		if (!sbuf)
   816			return -1;
   817	
   818		ptr = (char __user *)args[0];
   819	
   820		*buffer = trace_user_fault_read(&sbuf->buf, ptr, 4, NULL, NULL);
   821		if (!*buffer)
   822			return -1;
   823	
   824		/* Add room for the value */
   825		*size += 4;
   826	
   827		buf = *buffer;
   828	
   829		return 0;
   830	}
   831	

-- 
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https://github.com/intel/lkp-tests/wiki