Re: [PATCH] fprobe: Add unregister_fprobe_sync() for synchronous unregistration

Re: [PATCH] fprobe: Add unregister_fprobe_sync() for synchronous unregistration

[kernel test robot]

Hi Masami,

kernel test robot noticed the following build errors:

[auto build test ERROR on trace/for-next]
[cannot apply to linus/master v7.1-rc1 next-20260430]
[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/Masami-Hiramatsu-Google/fprobe-Add-unregister_fprobe_sync-for-synchronous-unregistration/20260427-214258
base:   https://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace for-next
patch link:    https://lore.kernel.org/r/177729179863.401400.6063130067239479972.stgit%40mhiramat.tok.corp.google.com
patch subject: [PATCH] fprobe: Add unregister_fprobe_sync() for synchronous unregistration
config: s390-allmodconfig (https://download.01.org/0day-ci/archive/20260503/202605031133.LJkoT4xo-lkp@intel.com/config)
compiler: clang version 18.1.8 (https://github.com/llvm/llvm-project 3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260503/202605031133.LJkoT4xo-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/202605031133.LJkoT4xo-lkp@intel.com/

All errors (new ones prefixed by >>):

>> kernel/trace/fprobe.c:983:14: error: call to undeclared function 'fprobe_registered'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     983 |         if (!fp || !fprobe_registered(fp))
         |                     ^
>> kernel/trace/fprobe.c:986:8: error: call to undeclared function 'unregister_fprobe_nolock'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     986 |         ret = unregister_fprobe_nolock(fp);
         |               ^
   kernel/trace/fprobe.c:986:8: note: did you mean 'unregister_fprobe_sync'?
   kernel/trace/fprobe.c:978:5: note: 'unregister_fprobe_sync' declared here
     978 | int unregister_fprobe_sync(struct fprobe *fp)
         |     ^
     979 | {
     980 |         int ret;
     981 | 
     982 |         guard(mutex)(&fprobe_mutex);
     983 |         if (!fp || !fprobe_registered(fp))
     984 |                 return -EINVAL;
     985 | 
     986 |         ret = unregister_fprobe_nolock(fp);
         |               ~~~~~~~~~~~~~~~~~~~~~~~~
         |               unregister_fprobe_sync
   2 errors generated.


vim +/fprobe_registered +983 kernel/trace/fprobe.c

   967	
   968	/**
   969	 * unregister_fprobe_sync() - Unregister fprobe synchronously with RCU grace period.
   970	 * @fp: A fprobe data structure to be unregistered.
   971	 *
   972	 * Unregister fprobe (and remove ftrace hooks from the function entries) and
   973	 * wait for the RCU grace period to finish. This is useful for preventing
   974	 * the fprobe from being used after it is unregistered.
   975	 *
   976	 * Return 0 if @fp is unregistered successfully, -errno if not.
   977	 */
   978	int unregister_fprobe_sync(struct fprobe *fp)
   979	{
   980		int ret;
   981	
   982		guard(mutex)(&fprobe_mutex);
 > 983		if (!fp || !fprobe_registered(fp))
   984			return -EINVAL;
   985	
 > 986		ret = unregister_fprobe_nolock(fp);
   987		if (ret)
   988			return ret;
   989	
   990		synchronize_rcu();
   991		return 0;
   992	}
   993	EXPORT_SYMBOL_GPL(unregister_fprobe_sync);
   994	

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