Re: [PATCH] tracing: Add system trigger file to enable triggers for all the system's events

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

Hi Steven,

kernel test robot noticed the following build warnings:

[auto build test WARNING on trace/for-next]
[also build test WARNING on linus/master v6.18-rc6 next-20251121]
[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-Add-system-trigger-file-to-enable-triggers-for-all-the-system-s-events/20251121-050454
base:   https://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace for-next
patch link:    https://lore.kernel.org/r/20251120160003.2fa33d80%40gandalf.local.home
patch subject: [PATCH] tracing: Add system trigger file to enable triggers for all the system's events
config: sparc64-defconfig (https://download.01.org/0day-ci/archive/20251122/202511220730.PQFWRcck-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/20251122/202511220730.PQFWRcck-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/202511220730.PQFWRcck-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> kernel/trace/trace_events_trigger.c:432:6: warning: variable 'len' set but not used [-Wunused-but-set-variable]
     432 |         int len;
         |             ^
   1 warning generated.


vim +/len +432 kernel/trace/trace_events_trigger.c

   420	
   421	static ssize_t
   422	event_system_trigger_write(struct file *filp, const char __user *ubuf,
   423			    size_t cnt, loff_t *ppos)
   424	{
   425		struct trace_subsystem_dir *dir = filp->private_data;
   426		struct event_command *p;
   427		char *command, *next;
   428		char *buf __free(kfree) = get_user_buf(ubuf, cnt);
   429		bool remove = false;
   430		bool found = false;
   431		ssize_t ret;
 > 432		int len;
   433	
   434		if (!buf)
   435			return 0;
   436	
   437		if (IS_ERR(buf))
   438			return PTR_ERR(buf);
   439	
   440		/* system triggers are not allowed to have counters */
   441		if (strchr(buf, ':'))
   442			return -EINVAL;
   443	
   444		/* If opened for read too, dir is in the seq_file descriptor */
   445		if (filp->f_mode & FMODE_READ) {
   446			struct seq_file *m = filp->private_data;
   447			dir = m->private;
   448		}
   449	
   450		/* Skip added space at beginning of buf */
   451		next = buf;
   452		strim(next);
   453	
   454		command = strsep(&next, " \t");
   455		if (next) {
   456			next = skip_spaces(next);
   457			if (!*next)
   458				next = NULL;
   459		}
   460		if (command[0] == '!') {
   461			remove = true;
   462			command++;
   463		}
   464	
   465		len = strlen(command);
   466		if (next)
   467			len += strlen(next) + 1;
   468	
   469		guard(mutex)(&event_mutex);
   470		guard(mutex)(&trigger_cmd_mutex);
   471	
   472		list_for_each_entry(p, &trigger_commands, list) {
   473			/* Allow to remove any trigger */
   474			if (!remove && !(p->flags & EVENT_CMD_FL_SYSTEM))
   475				continue;
   476			if (strcmp(p->name, command) == 0) {
   477				found = true;
   478				ret = process_system_events(dir, p, buf, command, next);
   479				break;
   480			}
   481		}
   482	
   483		if (!found)
   484			ret = -ENODEV;
   485	
   486		if (!ret)
   487			*ppos += cnt;
   488	
   489		if (remove || ret < 0)
   490			return ret ? : cnt;
   491	
   492		return cnt;
   493	}
   494	

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