[ast:timer 4/4] kernel/bpf/helpers.c:1022:6: warning: variable 'ret' set but not used

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

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tree:   https://git.kernel.org/pub/scm/linux/kernel/git/ast/bpf.git timer
head:   eb86df61cd52ea2e05357f8ae2b77e9bf6d63463
commit: eb86df61cd52ea2e05357f8ae2b77e9bf6d63463 [4/4] bpf: Implement verifier support for validation of async callbacks.
config: parisc-randconfig-s032-20210622 (attached as .config)
compiler: hppa-linux-gcc (GCC) 9.3.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # apt-get install sparse
        # sparse version: v0.6.3-341-g8af24329-dirty
        # https://git.kernel.org/pub/scm/linux/kernel/git/ast/bpf.git/commit/?id=eb86df61cd52ea2e05357f8ae2b77e9bf6d63463
        git remote add ast https://git.kernel.org/pub/scm/linux/kernel/git/ast/bpf.git
        git fetch --no-tags ast timer
        git checkout eb86df61cd52ea2e05357f8ae2b77e9bf6d63463
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' W=1 ARCH=parisc 

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

All warnings (new ones prefixed by >>):

   kernel/bpf/helpers.c: In function 'bpf_timer_cb':
>> kernel/bpf/helpers.c:1022:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
    1022 |  int ret;
         |      ^~~
   In file included from <command-line>:
   In function '____bpf_timer_init',
       inlined from 'bpf_timer_init' at kernel/bpf/helpers.c:1064:1:
   include/linux/compiler_types.h:328:38: error: call to '__compiletime_assert_353' declared with attribute error: BUILD_BUG_ON failed: __alignof__(struct bpf_timer_kern) != __alignof__(struct bpf_timer)
     328 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
         |                                      ^
   include/linux/compiler_types.h:309:4: note: in definition of macro '__compiletime_assert'
     309 |    prefix ## suffix();    \
         |    ^~~~~~
   include/linux/compiler_types.h:328:2: note: in expansion of macro '_compiletime_assert'
     328 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
         |  ^~~~~~~~~~~~~~~~~~~
   include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
      39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
         |                                     ^~~~~~~~~~~~~~~~~~
   include/linux/build_bug.h:50:2: note: in expansion of macro 'BUILD_BUG_ON_MSG'
      50 |  BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
         |  ^~~~~~~~~~~~~~~~
   kernel/bpf/helpers.c:1073:2: note: in expansion of macro 'BUILD_BUG_ON'
    1073 |  BUILD_BUG_ON(__alignof__(struct bpf_timer_kern) != __alignof__(struct bpf_timer));
         |  ^~~~~~~~~~~~


vim +/ret +1022 kernel/bpf/helpers.c

7e26a76313f427 Alexei Starovoitov 2021-05-17  1011  
7e26a76313f427 Alexei Starovoitov 2021-05-17  1012  static enum hrtimer_restart bpf_timer_cb(struct hrtimer *hrtimer)
7e26a76313f427 Alexei Starovoitov 2021-05-17  1013  {
7e26a76313f427 Alexei Starovoitov 2021-05-17  1014  	struct bpf_hrtimer *t = container_of(hrtimer, struct bpf_hrtimer, timer);
7e26a76313f427 Alexei Starovoitov 2021-05-17  1015  	struct bpf_map *map = t->map;
7e26a76313f427 Alexei Starovoitov 2021-05-17  1016  	void *value = t->value;
7e26a76313f427 Alexei Starovoitov 2021-05-17  1017  	struct bpf_timer_kern *timer = value + map->timer_off;
7e26a76313f427 Alexei Starovoitov 2021-05-17  1018  	struct bpf_prog *prog;
7e26a76313f427 Alexei Starovoitov 2021-05-17  1019  	void *callback_fn;
7e26a76313f427 Alexei Starovoitov 2021-05-17  1020  	void *key;
7e26a76313f427 Alexei Starovoitov 2021-05-17  1021  	u32 idx;
7e26a76313f427 Alexei Starovoitov 2021-05-17 @1022  	int ret;
7e26a76313f427 Alexei Starovoitov 2021-05-17  1023  
7e26a76313f427 Alexei Starovoitov 2021-05-17  1024  	____bpf_spin_lock(&timer->lock);
7e26a76313f427 Alexei Starovoitov 2021-05-17  1025  	/* callback_fn and prog need to match. They're updated together
7e26a76313f427 Alexei Starovoitov 2021-05-17  1026  	 * and have to be read under lock.
7e26a76313f427 Alexei Starovoitov 2021-05-17  1027  	 */
7e26a76313f427 Alexei Starovoitov 2021-05-17  1028  	prog = t->prog;
7e26a76313f427 Alexei Starovoitov 2021-05-17  1029  	callback_fn = t->callback_fn;
7e26a76313f427 Alexei Starovoitov 2021-05-17  1030  
7e26a76313f427 Alexei Starovoitov 2021-05-17  1031  	/* wrap bpf subprog invocation with prog->refcnt++ and -- to make
7e26a76313f427 Alexei Starovoitov 2021-05-17  1032  	 * sure that refcnt doesn't become zero when subprog is executing.
7e26a76313f427 Alexei Starovoitov 2021-05-17  1033  	 * Do it under lock to make sure that bpf_timer_start doesn't drop
7e26a76313f427 Alexei Starovoitov 2021-05-17  1034  	 * prev prog refcnt to zero before timer_cb has a chance to bump it.
7e26a76313f427 Alexei Starovoitov 2021-05-17  1035  	 */
7e26a76313f427 Alexei Starovoitov 2021-05-17  1036  	bpf_prog_inc(prog);
7e26a76313f427 Alexei Starovoitov 2021-05-17  1037  	____bpf_spin_unlock(&timer->lock);
7e26a76313f427 Alexei Starovoitov 2021-05-17  1038  
7e26a76313f427 Alexei Starovoitov 2021-05-17  1039  	/* bpf_timer_cb() runs in hrtimer_run_softirq. It doesn't migrate and
7e26a76313f427 Alexei Starovoitov 2021-05-17  1040  	 * cannot be preempted by another bpf_timer_cb() on the same cpu.
7e26a76313f427 Alexei Starovoitov 2021-05-17  1041  	 * Remember the timer this callback is servicing to prevent
7e26a76313f427 Alexei Starovoitov 2021-05-17  1042  	 * deadlock if callback_fn() calls bpf_timer_cancel() on the same timer.
7e26a76313f427 Alexei Starovoitov 2021-05-17  1043  	 */
7e26a76313f427 Alexei Starovoitov 2021-05-17  1044  	this_cpu_write(hrtimer_running, t);
7e26a76313f427 Alexei Starovoitov 2021-05-17  1045  	if (map->map_type == BPF_MAP_TYPE_ARRAY) {
7e26a76313f427 Alexei Starovoitov 2021-05-17  1046  		struct bpf_array *array = container_of(map, struct bpf_array, map);
7e26a76313f427 Alexei Starovoitov 2021-05-17  1047  
7e26a76313f427 Alexei Starovoitov 2021-05-17  1048  		/* compute the key */
7e26a76313f427 Alexei Starovoitov 2021-05-17  1049  		idx = ((char *)value - array->value) / array->elem_size;
7e26a76313f427 Alexei Starovoitov 2021-05-17  1050  		key = &idx;
7e26a76313f427 Alexei Starovoitov 2021-05-17  1051  	} else { /* hash or lru */
7e26a76313f427 Alexei Starovoitov 2021-05-17  1052  		key = value - round_up(map->key_size, 8);
7e26a76313f427 Alexei Starovoitov 2021-05-17  1053  	}
7e26a76313f427 Alexei Starovoitov 2021-05-17  1054  
7e26a76313f427 Alexei Starovoitov 2021-05-17  1055  	ret = BPF_CAST_CALL(callback_fn)((u64)(long)map,
7e26a76313f427 Alexei Starovoitov 2021-05-17  1056  					 (u64)(long)key,
7e26a76313f427 Alexei Starovoitov 2021-05-17  1057  					 (u64)(long)value, 0, 0);
7e26a76313f427 Alexei Starovoitov 2021-05-17  1058  	bpf_prog_put(prog);
7e26a76313f427 Alexei Starovoitov 2021-05-17  1059  
7e26a76313f427 Alexei Starovoitov 2021-05-17  1060  	this_cpu_write(hrtimer_running, NULL);
7e26a76313f427 Alexei Starovoitov 2021-05-17  1061  	return HRTIMER_NORESTART;
7e26a76313f427 Alexei Starovoitov 2021-05-17  1062  }
7e26a76313f427 Alexei Starovoitov 2021-05-17  1063  

:::::: The code at line 1022 was first introduced by commit
:::::: 7e26a76313f4274c6013a7565411f3f7b6773b29 bpf: Introduce bpf_timer

:::::: TO: Alexei Starovoitov <ast@kernel.org>
:::::: CC: Alexei Starovoitov <ast@kernel.org>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org

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