Re: [PATCH net-next] sfc: trace_xdp_exception on XDP failure

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

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Hi Arthur,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on net-next/master]
[also build test WARNING on next-20191112]
[cannot apply to v5.4-rc7]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Arthur-Fabre/sfc-trace_xdp_exception-on-XDP-failure/20191113-021808
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git ca22d6977b9b4ab0fd2e7909b57e32ba5b95046f
config: mips-allmodconfig (attached as .config)
compiler: mips-linux-gcc (GCC) 7.4.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=7.4.0 make.cross ARCH=mips 

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

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   In file included from include/trace/events/xdp.h:10:0,
                    from include/linux/bpf_trace.h:5,
                    from drivers/net/ethernet/sfc/rx.c:21:
   drivers/net/ethernet/sfc/rx.c: In function '__efx_rx_packet':
>> include/linux/tracepoint.h:193:6: warning: 'xdp_act' may be used uninitialized in this function [-Wmaybe-uninitialized]
        ((void(*)(proto))(it_func))(args); \
         ^
   drivers/net/ethernet/sfc/rx.c:658:6: note: 'xdp_act' was declared here
     u32 xdp_act;
         ^~~~~~~
--
   In file included from include/trace/events/xdp.h:10:0,
                    from include/linux/bpf_trace.h:5,
                    from drivers/net//ethernet/sfc/rx.c:21:
   drivers/net//ethernet/sfc/rx.c: In function '__efx_rx_packet':
>> include/linux/tracepoint.h:193:6: warning: 'xdp_act' may be used uninitialized in this function [-Wmaybe-uninitialized]
        ((void(*)(proto))(it_func))(args); \
         ^
   drivers/net//ethernet/sfc/rx.c:658:6: note: 'xdp_act' was declared here
     u32 xdp_act;
         ^~~~~~~

vim +/xdp_act +193 include/linux/tracepoint.h

97e1c18e8d17bd Mathieu Desnoyers       2008-07-18  151  
97e1c18e8d17bd Mathieu Desnoyers       2008-07-18  152  /*
97e1c18e8d17bd Mathieu Desnoyers       2008-07-18  153   * it_func[0] is never NULL because there is at least one element in the array
97e1c18e8d17bd Mathieu Desnoyers       2008-07-18  154   * when the array itself is non NULL.
38516ab59fbc5b Steven Rostedt          2010-04-20  155   *
38516ab59fbc5b Steven Rostedt          2010-04-20  156   * Note, the proto and args passed in includes "__data" as the first parameter.
38516ab59fbc5b Steven Rostedt          2010-04-20  157   * The reason for this is to handle the "void" prototype. If a tracepoint
38516ab59fbc5b Steven Rostedt          2010-04-20  158   * has a "void" prototype, then it is invalid to declare a function
38516ab59fbc5b Steven Rostedt          2010-04-20  159   * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
38516ab59fbc5b Steven Rostedt          2010-04-20  160   * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
97e1c18e8d17bd Mathieu Desnoyers       2008-07-18  161   */
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  162) #define __DO_TRACE(tp, proto, args, cond, rcuidle)			\
97e1c18e8d17bd Mathieu Desnoyers       2008-07-18  163  	do {								\
38516ab59fbc5b Steven Rostedt          2010-04-20  164  		struct tracepoint_func *it_func_ptr;			\
38516ab59fbc5b Steven Rostedt          2010-04-20  165  		void *it_func;						\
38516ab59fbc5b Steven Rostedt          2010-04-20  166  		void *__data;						\
0c7a52e4d4b5c4 Zenghui Yu              2018-11-28  167  		int __maybe_unused __idx = 0;				\
97e1c18e8d17bd Mathieu Desnoyers       2008-07-18  168  									\
287050d3902644 Steven Rostedt          2010-12-02  169  		if (!(cond))						\
287050d3902644 Steven Rostedt          2010-12-02  170  			return;						\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  171) 									\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  172) 		/* srcu can't be used from NMI */			\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  173) 		WARN_ON_ONCE(rcuidle && in_nmi());			\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  174) 									\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  175) 		/* keep srcu and sched-rcu usage consistent */		\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  176) 		preempt_disable_notrace();				\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  177) 									\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  178) 		/*							\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  179) 		 * For rcuidle callers, use srcu since sched-rcu	\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  180) 		 * doesn't work from the idle path.			\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  181) 		 */							\
865e63b04e9b2a Steven Rostedt (VMware  2018-09-04  182) 		if (rcuidle) {						\
0c7a52e4d4b5c4 Zenghui Yu              2018-11-28  183  			__idx = srcu_read_lock_notrace(&tracepoint_srcu);\
865e63b04e9b2a Steven Rostedt (VMware  2018-09-04  184) 			rcu_irq_enter_irqson();				\
865e63b04e9b2a Steven Rostedt (VMware  2018-09-04  185) 		}							\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  186) 									\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  187) 		it_func_ptr = rcu_dereference_raw((tp)->funcs);		\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  188) 									\
38516ab59fbc5b Steven Rostedt          2010-04-20  189  		if (it_func_ptr) {					\
97e1c18e8d17bd Mathieu Desnoyers       2008-07-18  190  			do {						\
38516ab59fbc5b Steven Rostedt          2010-04-20  191  				it_func = (it_func_ptr)->func;		\
38516ab59fbc5b Steven Rostedt          2010-04-20  192  				__data = (it_func_ptr)->data;		\
38516ab59fbc5b Steven Rostedt          2010-04-20 @193  				((void(*)(proto))(it_func))(args);	\
38516ab59fbc5b Steven Rostedt          2010-04-20  194  			} while ((++it_func_ptr)->func);		\
97e1c18e8d17bd Mathieu Desnoyers       2008-07-18  195  		}							\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  196) 									\
865e63b04e9b2a Steven Rostedt (VMware  2018-09-04  197) 		if (rcuidle) {						\
865e63b04e9b2a Steven Rostedt (VMware  2018-09-04  198) 			rcu_irq_exit_irqson();				\
0c7a52e4d4b5c4 Zenghui Yu              2018-11-28  199  			srcu_read_unlock_notrace(&tracepoint_srcu, __idx);\
865e63b04e9b2a Steven Rostedt (VMware  2018-09-04  200) 		}							\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  201) 									\
e6753f23d961d6 Joel Fernandes (Google  2018-07-30  202) 		preempt_enable_notrace();				\
97e1c18e8d17bd Mathieu Desnoyers       2008-07-18  203  	} while (0)
97e1c18e8d17bd Mathieu Desnoyers       2008-07-18  204  

:::::: The code at line 193 was first introduced by commit
:::::: 38516ab59fbc5b3bb278cf5e1fe2867c70cff32e tracing: Let tracepoints have data passed to tracepoint callbacks

:::::: TO: Steven Rostedt <srostedt@redhat.com>
:::::: CC: Steven Rostedt <rostedt@goodmis.org>

---
0-DAY kernel test infrastructure                 Open Source Technology Center
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org Intel Corporation

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