Re: [PATCH] trace_branch: use per-cpu counters for correct/incorrect stats

Re: [PATCH] trace_branch: use per-cpu counters for correct/incorrect stats

[kernel test robot]

Hi Martin,

kernel test robot noticed the following build warnings:

[auto build test WARNING on trace/for-next]
[also build test WARNING on linus/master v7.2-rc6 next-20260806]
[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/Martin-Weiss/trace_branch-use-per-cpu-counters-for-correct-incorrect-stats/20260806-093445
base:   https://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace for-next
patch link:    https://lore.kernel.org/r/20260629095838.601926-1-Martin.weiss2410%40gmail.com
patch subject: [PATCH] trace_branch: use per-cpu counters for correct/incorrect stats
config: hexagon-randconfig-002-20260807 (https://download.01.org/0day-ci/archive/20260807/202608070317.EiUZyapo-lkp@intel.com/config)
compiler: clang version 24.0.0git (https://github.com/llvm/llvm-project 12df34b8469b8095359de8c249cb1b2753fadeea)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260807/202608070317.EiUZyapo-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/202608070317.EiUZyapo-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> kernel/trace/trace_branch.c:200:1: warning: all paths through this function will call itself [-Winfinite-recursion]
     200 | {
         | ^
   1 warning generated.


vim +200 kernel/trace/trace_branch.c

52f232cb720a7b kernel/trace/trace_unlikely.c Steven Rostedt          2008-11-12  197  
134e6a034cb004 kernel/trace/trace_branch.c   Steven Rostedt (VMware  2017-01-19  198) void ftrace_likely_update(struct ftrace_likely_data *f, int val,
d45ae1f7041ac5 kernel/trace/trace_branch.c   Steven Rostedt (VMware  2017-01-17  199) 			  int expect, int is_constant)
1f0d69a9fc815d kernel/trace/trace_unlikely.c Steven Rostedt          2008-11-12 @200  {
4a6c91fbdef846 kernel/trace/trace_branch.c   Peter Zijlstra          2019-03-07  201  	unsigned long flags = user_access_save();
4a6c91fbdef846 kernel/trace/trace_branch.c   Peter Zijlstra          2019-03-07  202  
d45ae1f7041ac5 kernel/trace/trace_branch.c   Steven Rostedt (VMware  2017-01-17  203) 	/* A constant is always correct */
134e6a034cb004 kernel/trace/trace_branch.c   Steven Rostedt (VMware  2017-01-19  204) 	if (is_constant) {
134e6a034cb004 kernel/trace/trace_branch.c   Steven Rostedt (VMware  2017-01-19  205) 		f->constant++;
d45ae1f7041ac5 kernel/trace/trace_branch.c   Steven Rostedt (VMware  2017-01-17  206) 		val = expect;
134e6a034cb004 kernel/trace/trace_branch.c   Steven Rostedt (VMware  2017-01-19  207) 	}
52f232cb720a7b kernel/trace/trace_unlikely.c Steven Rostedt          2008-11-12  208  	/*
52f232cb720a7b kernel/trace/trace_unlikely.c Steven Rostedt          2008-11-12  209  	 * I would love to have a trace point here instead, but the
52f232cb720a7b kernel/trace/trace_unlikely.c Steven Rostedt          2008-11-12  210  	 * trace point code is so inundated with unlikely and likely
52f232cb720a7b kernel/trace/trace_unlikely.c Steven Rostedt          2008-11-12  211  	 * conditions that the recursive nightmare that exists is too
52f232cb720a7b kernel/trace/trace_unlikely.c Steven Rostedt          2008-11-12  212  	 * much to try to get working. At least for now.
52f232cb720a7b kernel/trace/trace_unlikely.c Steven Rostedt          2008-11-12  213  	 */
068f530b3f274d kernel/trace/trace_branch.c   Steven Rostedt (VMware  2017-01-19  214) 	trace_likely_condition(f, val, expect);
52f232cb720a7b kernel/trace/trace_unlikely.c Steven Rostedt          2008-11-12  215  
a53c1587fa9e39 kernel/trace/trace_branch.c   Martin Weiss            2026-06-29  216  	/* use per-cpu counters to avoid contention */
1f0d69a9fc815d kernel/trace/trace_unlikely.c Steven Rostedt          2008-11-12  217  	if (val == expect)
a53c1587fa9e39 kernel/trace/trace_branch.c   Martin Weiss            2026-06-29  218  		this_cpu_inc(f->data.correct);
1f0d69a9fc815d kernel/trace/trace_unlikely.c Steven Rostedt          2008-11-12  219  	else
a53c1587fa9e39 kernel/trace/trace_branch.c   Martin Weiss            2026-06-29  220  		this_cpu_inc(f->data.incorrect);
4a6c91fbdef846 kernel/trace/trace_branch.c   Peter Zijlstra          2019-03-07  221  
4a6c91fbdef846 kernel/trace/trace_branch.c   Peter Zijlstra          2019-03-07  222  	user_access_restore(flags);
1f0d69a9fc815d kernel/trace/trace_unlikely.c Steven Rostedt          2008-11-12  223  }
1f0d69a9fc815d kernel/trace/trace_unlikely.c Steven Rostedt          2008-11-12  224  EXPORT_SYMBOL(ftrace_likely_update);
1f0d69a9fc815d kernel/trace/trace_unlikely.c Steven Rostedt          2008-11-12  225  

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