Re: [PATCH v4 bpf-next 2/4] ftrace: allow IPMODIFY and DIRECT ops on the same function

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

Hi Song,

I love your patch! Perhaps something to improve:

[auto build test WARNING on bpf-next/master]

url:    https://github.com/intel-lab-lkp/linux/commits/Song-Liu/ftrace-host-klp-and-bpf-trampoline-together/20220718-135652
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: x86_64-randconfig-a004 (https://download.01.org/0day-ci/archive/20220718/202207181552.VuKfz9zg-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-3) 11.3.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/9ef1ec8cb818d8ca70887c8c123f2d579384a6c6
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Song-Liu/ftrace-host-klp-and-bpf-trampoline-together/20220718-135652
        git checkout 9ef1ec8cb818d8ca70887c8c123f2d579384a6c6
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash kernel/trace/

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   kernel/trace/ftrace.c: In function 'register_ftrace_function':
>> kernel/trace/ftrace.c:8197:14: warning: variable 'direct_mutex_locked' set but not used [-Wunused-but-set-variable]
    8197 |         bool direct_mutex_locked = false;
         |              ^~~~~~~~~~~~~~~~~~~


vim +/direct_mutex_locked +8197 kernel/trace/ftrace.c

  8182	
  8183	/**
  8184	 * register_ftrace_function - register a function for profiling
  8185	 * @ops:	ops structure that holds the function for profiling.
  8186	 *
  8187	 * Register a function to be called by all functions in the
  8188	 * kernel.
  8189	 *
  8190	 * Note: @ops->func and all the functions it calls must be labeled
  8191	 *       with "notrace", otherwise it will go into a
  8192	 *       recursive loop.
  8193	 */
  8194	int register_ftrace_function(struct ftrace_ops *ops)
  8195		__releases(&direct_mutex)
  8196	{
> 8197		bool direct_mutex_locked = false;
  8198		int ret;
  8199	
  8200		ftrace_ops_init(ops);
  8201	
  8202		ret = prepare_direct_functions_for_ipmodify(ops);
  8203		if (ret < 0)
  8204			return ret;
  8205		else if (ret == 1)
  8206			direct_mutex_locked = true;
  8207	
  8208		mutex_lock(&ftrace_lock);
  8209	
  8210		ret = ftrace_startup(ops, 0);
  8211	
  8212		mutex_unlock(&ftrace_lock);
  8213	

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