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Date:   Wed, 16 Aug 2023 09:07:48 -0500
From:   David Vernet <void@manifault.com>
To:     kernel test robot <lkp@intel.com>
Cc:     oe-kbuild-all@lists.linux.dev, linux-kernel@vger.kernel.org,
        Alexei Starovoitov <ast@kernel.org>
Subject: Re: kernel/bpf/cpumask.c:41:21: warning: no previous declaration for
 'bpf_cpumask_create'
Message-ID: <20230816140748.GA759901@maniforge>
References: <202308162115.Hn23vv3n-lkp@intel.com>
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On Wed, Aug 16, 2023 at 09:25:30PM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   4853c74bd7ab7fdb83f319bd9ace8a08c031e9b6
> commit: 516f4d3397c9e90f4da04f59986c856016269aa1 bpf: Enable cpumasks to be queried and used as kptrs
> date:   7 months ago
> config: x86_64-randconfig-x076-20230816 (https://download.01.org/0day-ci/archive/20230816/202308162115.Hn23vv3n-lkp@intel.com/config)
> compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
> reproduce: (https://download.01.org/0day-ci/archive/20230816/202308162115.Hn23vv3n-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/202308162115.Hn23vv3n-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
> >> kernel/bpf/cpumask.c:41:21: warning: no previous declaration for 'bpf_cpumask_create' [-Wmissing-declarations]
>     struct bpf_cpumask *bpf_cpumask_create(void)

Meh, more noise from lkp because of kfuncs. It would be nice if as a
courtesy, these warnings were fixed before they got turned on and the
email list got spammed 7 months after the commit landed; especially
given that this is essentially redundant with -Wmissing-prototypes.

Anyways, the solution here is to just add the following around all
kfuncs that already have -Wmissing-prototypes disabled:

__diag_push();
__diag_ignore_all("-Wmissing-declarations",
                  "Global kfuncs as their definitions will be in BTF");

I'll send out a patch that adds this around all kfuncs so we can avoid
all of these warnings in one go.

>                         ^~~~~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:55:21: warning: no previous declaration for 'bpf_cpumask_acquire' [-Wmissing-declarations]
>     struct bpf_cpumask *bpf_cpumask_acquire(struct bpf_cpumask *cpumask)
>                         ^~~~~~~~~~~~~~~~~~~
>    kernel/bpf/cpumask.c:61:21: warning: no previous declaration for 'bpf_cpumask_kptr_get' [-Wmissing-declarations]
>     struct bpf_cpumask *bpf_cpumask_kptr_get(struct bpf_cpumask **cpumaskp)
>                         ^~~~~~~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:79:6: warning: no previous declaration for 'bpf_cpumask_release' [-Wmissing-declarations]
>     void bpf_cpumask_release(struct bpf_cpumask *cpumask)
>          ^~~~~~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:91:5: warning: no previous declaration for 'bpf_cpumask_first' [-Wmissing-declarations]
>     u32 bpf_cpumask_first(const struct cpumask *cpumask)
>         ^~~~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:96:5: warning: no previous declaration for 'bpf_cpumask_first_zero' [-Wmissing-declarations]
>     u32 bpf_cpumask_first_zero(const struct cpumask *cpumask)
>         ^~~~~~~~~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:101:6: warning: no previous declaration for 'bpf_cpumask_set_cpu' [-Wmissing-declarations]
>     void bpf_cpumask_set_cpu(u32 cpu, struct bpf_cpumask *cpumask)
>          ^~~~~~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:109:6: warning: no previous declaration for 'bpf_cpumask_clear_cpu' [-Wmissing-declarations]
>     void bpf_cpumask_clear_cpu(u32 cpu, struct bpf_cpumask *cpumask)
>          ^~~~~~~~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:117:6: warning: no previous declaration for 'bpf_cpumask_test_cpu' [-Wmissing-declarations]
>     bool bpf_cpumask_test_cpu(u32 cpu, const struct cpumask *cpumask)
>          ^~~~~~~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:125:6: warning: no previous declaration for 'bpf_cpumask_test_and_set_cpu' [-Wmissing-declarations]
>     bool bpf_cpumask_test_and_set_cpu(u32 cpu, struct bpf_cpumask *cpumask)
>          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:133:6: warning: no previous declaration for 'bpf_cpumask_test_and_clear_cpu' [-Wmissing-declarations]
>     bool bpf_cpumask_test_and_clear_cpu(u32 cpu, struct bpf_cpumask *cpumask)
>          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:141:6: warning: no previous declaration for 'bpf_cpumask_setall' [-Wmissing-declarations]
>     void bpf_cpumask_setall(struct bpf_cpumask *cpumask)
>          ^~~~~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:146:6: warning: no previous declaration for 'bpf_cpumask_clear' [-Wmissing-declarations]
>     void bpf_cpumask_clear(struct bpf_cpumask *cpumask)
>          ^~~~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:151:6: warning: no previous declaration for 'bpf_cpumask_and' [-Wmissing-declarations]
>     bool bpf_cpumask_and(struct bpf_cpumask *dst,
>          ^~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:158:6: warning: no previous declaration for 'bpf_cpumask_or' [-Wmissing-declarations]
>     void bpf_cpumask_or(struct bpf_cpumask *dst,
>          ^~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:165:6: warning: no previous declaration for 'bpf_cpumask_xor' [-Wmissing-declarations]
>     void bpf_cpumask_xor(struct bpf_cpumask *dst,
>          ^~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:172:6: warning: no previous declaration for 'bpf_cpumask_equal' [-Wmissing-declarations]
>     bool bpf_cpumask_equal(const struct cpumask *src1, const struct cpumask *src2)
>          ^~~~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:177:6: warning: no previous declaration for 'bpf_cpumask_intersects' [-Wmissing-declarations]
>     bool bpf_cpumask_intersects(const struct cpumask *src1, const struct cpumask *src2)
>          ^~~~~~~~~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:182:6: warning: no previous declaration for 'bpf_cpumask_subset' [-Wmissing-declarations]
>     bool bpf_cpumask_subset(const struct cpumask *src1, const struct cpumask *src2)
>          ^~~~~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:187:6: warning: no previous declaration for 'bpf_cpumask_empty' [-Wmissing-declarations]
>     bool bpf_cpumask_empty(const struct cpumask *cpumask)
>          ^~~~~~~~~~~~~~~~~
> >> kernel/bpf/cpumask.c:192:6: warning: no previous declaration for 'bpf_cpumask_full' [-Wmissing-declarations]
>     bool bpf_cpumask_full(const struct cpumask *cpumask)
>          ^~~~~~~~~~~~~~~~
>    kernel/bpf/cpumask.c:197:6: warning: no previous declaration for 'bpf_cpumask_copy' [-Wmissing-declarations]
>     void bpf_cpumask_copy(struct bpf_cpumask *dst, const struct cpumask *src)
>          ^~~~~~~~~~~~~~~~
>    kernel/bpf/cpumask.c:202:5: warning: no previous declaration for 'bpf_cpumask_any' [-Wmissing-declarations]
>     u32 bpf_cpumask_any(const struct cpumask *cpumask)
>         ^~~~~~~~~~~~~~~
>    kernel/bpf/cpumask.c:207:5: warning: no previous declaration for 'bpf_cpumask_any_and' [-Wmissing-declarations]
>     u32 bpf_cpumask_any_and(const struct cpumask *src1, const struct cpumask *src2)
>         ^~~~~~~~~~~~~~~~~~~
> 
> 
> vim +/bpf_cpumask_create +41 kernel/bpf/cpumask.c
> 
>     36	
>     37	__diag_push();
>     38	__diag_ignore_all("-Wmissing-prototypes",
>     39			  "Global kfuncs as their definitions will be in BTF");
>     40	
>   > 41	struct bpf_cpumask *bpf_cpumask_create(void)
>     42	{
>     43		struct bpf_cpumask *cpumask;
>     44	
>     45		cpumask = bpf_mem_alloc(&bpf_cpumask_ma, sizeof(*cpumask));
>     46		if (!cpumask)
>     47			return NULL;
>     48	
>     49		memset(cpumask, 0, sizeof(*cpumask));
>     50		refcount_set(&cpumask->usage, 1);
>     51	
>     52		return cpumask;
>     53	}
>     54	
>   > 55	struct bpf_cpumask *bpf_cpumask_acquire(struct bpf_cpumask *cpumask)
>     56	{
>     57		refcount_inc(&cpumask->usage);
>     58		return cpumask;
>     59	}
>     60	
>   > 61	struct bpf_cpumask *bpf_cpumask_kptr_get(struct bpf_cpumask **cpumaskp)
>     62	{
>     63		struct bpf_cpumask *cpumask;
>     64	
>     65		/* The BPF memory allocator frees memory backing its caches in an RCU
>     66		 * callback. Thus, we can safely use RCU to ensure that the cpumask is
>     67		 * safe to read.
>     68		 */
>     69		rcu_read_lock();
>     70	
>     71		cpumask = READ_ONCE(*cpumaskp);
>     72		if (cpumask && !refcount_inc_not_zero(&cpumask->usage))
>     73			cpumask = NULL;
>     74	
>     75		rcu_read_unlock();
>     76		return cpumask;
>     77	}
>     78	
>   > 79	void bpf_cpumask_release(struct bpf_cpumask *cpumask)
>     80	{
>     81		if (!cpumask)
>     82			return;
>     83	
>     84		if (refcount_dec_and_test(&cpumask->usage)) {
>     85			migrate_disable();
>     86			bpf_mem_free(&bpf_cpumask_ma, cpumask);
>     87			migrate_enable();
>     88		}
>     89	}
>     90	
>   > 91	u32 bpf_cpumask_first(const struct cpumask *cpumask)
>     92	{
>     93		return cpumask_first(cpumask);
>     94	}
>     95	
>   > 96	u32 bpf_cpumask_first_zero(const struct cpumask *cpumask)
>     97	{
>     98		return cpumask_first_zero(cpumask);
>     99	}
>    100	
>  > 101	void bpf_cpumask_set_cpu(u32 cpu, struct bpf_cpumask *cpumask)
>    102	{
>    103		if (!cpu_valid(cpu))
>    104			return;
>    105	
>    106		cpumask_set_cpu(cpu, (struct cpumask *)cpumask);
>    107	}
>    108	
>  > 109	void bpf_cpumask_clear_cpu(u32 cpu, struct bpf_cpumask *cpumask)
>    110	{
>    111		if (!cpu_valid(cpu))
>    112			return;
>    113	
>    114		cpumask_clear_cpu(cpu, (struct cpumask *)cpumask);
>    115	}
>    116	
>  > 117	bool bpf_cpumask_test_cpu(u32 cpu, const struct cpumask *cpumask)
>    118	{
>    119		if (!cpu_valid(cpu))
>    120			return false;
>    121	
>    122		return cpumask_test_cpu(cpu, (struct cpumask *)cpumask);
>    123	}
>    124	
>  > 125	bool bpf_cpumask_test_and_set_cpu(u32 cpu, struct bpf_cpumask *cpumask)
>    126	{
>    127		if (!cpu_valid(cpu))
>    128			return false;
>    129	
>    130		return cpumask_test_and_set_cpu(cpu, (struct cpumask *)cpumask);
>    131	}
>    132	
>  > 133	bool bpf_cpumask_test_and_clear_cpu(u32 cpu, struct bpf_cpumask *cpumask)
>    134	{
>    135		if (!cpu_valid(cpu))
>    136			return false;
>    137	
>    138		return cpumask_test_and_clear_cpu(cpu, (struct cpumask *)cpumask);
>    139	}
>    140	
>  > 141	void bpf_cpumask_setall(struct bpf_cpumask *cpumask)
>    142	{
>    143		cpumask_setall((struct cpumask *)cpumask);
>    144	}
>    145	
>  > 146	void bpf_cpumask_clear(struct bpf_cpumask *cpumask)
>    147	{
>    148		cpumask_clear((struct cpumask *)cpumask);
>    149	}
>    150	
>  > 151	bool bpf_cpumask_and(struct bpf_cpumask *dst,
>    152			     const struct cpumask *src1,
>    153			     const struct cpumask *src2)
>    154	{
>    155		return cpumask_and((struct cpumask *)dst, src1, src2);
>    156	}
>    157	
>  > 158	void bpf_cpumask_or(struct bpf_cpumask *dst,
>    159			    const struct cpumask *src1,
>    160			    const struct cpumask *src2)
>    161	{
>    162		cpumask_or((struct cpumask *)dst, src1, src2);
>    163	}
>    164	
>  > 165	void bpf_cpumask_xor(struct bpf_cpumask *dst,
>    166			     const struct cpumask *src1,
>    167			     const struct cpumask *src2)
>    168	{
>    169		cpumask_xor((struct cpumask *)dst, src1, src2);
>    170	}
>    171	
>  > 172	bool bpf_cpumask_equal(const struct cpumask *src1, const struct cpumask *src2)
>    173	{
>    174		return cpumask_equal(src1, src2);
>    175	}
>    176	
>  > 177	bool bpf_cpumask_intersects(const struct cpumask *src1, const struct cpumask *src2)
>    178	{
>    179		return cpumask_intersects(src1, src2);
>    180	}
>    181	
>  > 182	bool bpf_cpumask_subset(const struct cpumask *src1, const struct cpumask *src2)
>    183	{
>    184		return cpumask_subset(src1, src2);
>    185	}
>    186	
>  > 187	bool bpf_cpumask_empty(const struct cpumask *cpumask)
>    188	{
>    189		return cpumask_empty(cpumask);
>    190	}
>    191	
>  > 192	bool bpf_cpumask_full(const struct cpumask *cpumask)
>    193	{
>    194		return cpumask_full(cpumask);
>    195	}
>    196	
>  > 197	void bpf_cpumask_copy(struct bpf_cpumask *dst, const struct cpumask *src)
>    198	{
>    199		cpumask_copy((struct cpumask *)dst, src);
>    200	}
>    201	
> 
> -- 
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki