tree: https://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git ftrace/fgraph-multi head: 978dc256bd4d08df876d58b4fa01ba4cb3926242 commit: a436705d3d66255f8e32aa715dca3fcabe9cb0a9 [31/40] ftrace/function_graph: Pass fgraph_ops to function graph callbacks config: i386-randconfig-r035-20210416 (attached as .config) compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 reproduce (this is a W=1 build): # https://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git/c... git remote add trace https://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git git fetch --no-tags trace ftrace/fgraph-multi git checkout a436705d3d66255f8e32aa715dca3fcabe9cb0a9 # save the attached .config to linux build tree make W=1 W=1 ARCH=i386 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>): kernel/trace/fgraph.c:491:15: warning: no previous prototype for 'ftrace_return_to_handler' [-Wmissing-prototypes] 491 | unsigned long ftrace_return_to_handler(unsigned long frame_pointer) | ^~~~~~~~~~~~~~~~~~~~~~~~ kernel/trace/fgraph.c: In function 'ftrace_return_to_handler': kernel/trace/fgraph.c:493:27: warning: variable 'ret_stack' set but not used [-Wunused-but-set-variable] 493 | struct ftrace_ret_stack *ret_stack; | ^~~~~~~~~ kernel/trace/fgraph.c: At top level: kernel/trace/fgraph.c:635:6: warning: no previous prototype for 'ftrace_graph_sleep_time_control' [-Wmissing-prototypes] 635 | void ftrace_graph_sleep_time_control(bool enable) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 647 | trace_func_graph_ret_t ftrace_graph_return = ftrace_stub_graph; | ^~~~~~~~~~~~~~~~~ kernel/trace/fgraph.c: In function 'unregister_ftrace_graph': 909 | ftrace_graph_return = ftrace_stub_graph; | ^ cc1: some warnings being treated as errors vim +647 kernel/trace/fgraph.c b83b43ffc6e4b5 Steven Rostedt (VMware 2019-10-15 645) e73e679f656e67 Steven Rostedt (VMware 2018-11-15 646) /* The callbacks that hook a function */ 46f9469247c6f4 Steven Rostedt (VMware 2019-11-18 @647) trace_func_graph_ret_t ftrace_graph_return = ftrace_stub_graph; e73e679f656e67 Steven Rostedt (VMware 2018-11-15 648) trace_func_graph_ent_t ftrace_graph_entry = ftrace_graph_entry_stub; e73e679f656e67 Steven Rostedt (VMware 2018-11-15 649) :::::: The code at line 647 was first introduced by commit :::::: 46f9469247c6f4697cbbf37e4b3961120bf07f29 ftrace: Rename ftrace_graph_stub to ftrace_stub_graph :::::: TO: Steven Rostedt (VMware) <rostedt(a)goodmis.org&gt; :::::: CC: Steven Rostedt (VMware) <rostedt(a)goodmis.org&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org