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Date: Thu, 9 Feb 2017 16:01:04 +0800
From: kbuild test robot <lkp@...el.com>
To: Hoeun Ryu <hoeun.ryu@...il.com>
Cc: kbuild-all@...org, Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.com>, Ingo Molnar <mingo@...nel.org>,
	Andy Lutomirski <luto@...nel.org>,
	Kees Cook <keescook@...omium.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Mateusz Guzik <mguzik@...hat.com>, linux-kernel@...r.kernel.org,
	kernel-hardening@...ts.openwall.com,
	Hoeun Ryu <hoeun.ryu@...il.com>
Subject: Re: [PATCH v2 1/2] fork: free vmapped stacks in cache when cpus are
 offline

Hi Hoeun,

[auto build test WARNING on next-20170208]
[also build test WARNING on v4.10-rc7]
[cannot apply to linus/master linux/master v4.9-rc8 v4.9-rc7 v4.9-rc6]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Hoeun-Ryu/fork-free-vmapped-stacks-in-cache-when-cpus-are-offline/20170209-124143
config: i386-randconfig-x004-201706 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All warnings (new ones prefixed by >>):

   kernel/fork.c: In function 'free_vm_stack_cache':
   kernel/fork.c:177:18: error: 'NR_CACHED_STACKS' undeclared (first use in this function)
     for (i = 0; i < NR_CACHED_STACKS; i++) {
                     ^~~~~~~~~~~~~~~~
   kernel/fork.c:177:18: note: each undeclared identifier is reported only once for each function it appears in
   In file included from include/asm-generic/percpu.h:6:0,
                    from arch/x86/include/asm/percpu.h:542,
                    from arch/x86/include/asm/preempt.h:5,
                    from include/linux/preempt.h:59,
                    from include/linux/spinlock.h:50,
                    from include/linux/mmzone.h:7,
                    from include/linux/gfp.h:5,
                    from include/linux/slab.h:14,
                    from kernel/fork.c:14:
   kernel/fork.c:178:46: error: 'cached_stacks' undeclared (first use in this function)
      struct vm_struct *vm_stack = this_cpu_read(cached_stacks[i]);
                                                 ^
   include/linux/percpu-defs.h:305:9: note: in definition of macro '__pcpu_size_call_return'
     typeof(variable) pscr_ret__;     \
            ^~~~~~~~
   kernel/fork.c:178:32: note: in expansion of macro 'this_cpu_read'
      struct vm_struct *vm_stack = this_cpu_read(cached_stacks[i]);
                                   ^~~~~~~~~~~~~
   include/linux/percpu-defs.h:304:1: warning: initialization makes pointer from integer without a cast [-Wint-conversion]
    ({         \
    ^
   include/linux/percpu-defs.h:494:29: note: in expansion of macro '__pcpu_size_call_return'
    #define this_cpu_read(pcp)  __pcpu_size_call_return(this_cpu_read_, pcp)
                                ^~~~~~~~~~~~~~~~~~~~~~~
   kernel/fork.c:178:32: note: in expansion of macro 'this_cpu_read'
      struct vm_struct *vm_stack = this_cpu_read(cached_stacks[i]);
                                   ^~~~~~~~~~~~~
   In file included from arch/x86/include/asm/preempt.h:5:0,
                    from include/linux/preempt.h:59,
                    from include/linux/spinlock.h:50,
                    from include/linux/mmzone.h:7,
                    from include/linux/gfp.h:5,
                    from include/linux/slab.h:14,
                    from kernel/fork.c:14:
>> arch/x86/include/asm/percpu.h:94:13: warning: assignment makes integer from pointer without a cast [-Wint-conversion]
      pto_tmp__ = (val);   \
                ^
   arch/x86/include/asm/percpu.h:416:36: note: in expansion of macro 'percpu_to_op'
    #define this_cpu_write_1(pcp, val) percpu_to_op("mov", (pcp), val)
                                       ^~~~~~~~~~~~
   include/linux/percpu-defs.h:364:11: note: in expansion of macro 'this_cpu_write_1'
      case 1: stem##1(variable, __VA_ARGS__);break;  \
              ^~~~
   include/linux/percpu-defs.h:495:34: note: in expansion of macro '__pcpu_size_call'
    #define this_cpu_write(pcp, val) __pcpu_size_call(this_cpu_write_, pcp, val)
                                     ^~~~~~~~~~~~~~~~
>> kernel/fork.c:183:3: note: in expansion of macro 'this_cpu_write'
      this_cpu_write(cached_stacks[i], NULL);
      ^~~~~~~~~~~~~~
>> arch/x86/include/asm/percpu.h:94:13: warning: assignment makes integer from pointer without a cast [-Wint-conversion]
      pto_tmp__ = (val);   \
                ^
   arch/x86/include/asm/percpu.h:417:36: note: in expansion of macro 'percpu_to_op'
    #define this_cpu_write_2(pcp, val) percpu_to_op("mov", (pcp), val)
                                       ^~~~~~~~~~~~
   include/linux/percpu-defs.h:365:11: note: in expansion of macro 'this_cpu_write_2'
      case 2: stem##2(variable, __VA_ARGS__);break;  \
              ^~~~
   include/linux/percpu-defs.h:495:34: note: in expansion of macro '__pcpu_size_call'
    #define this_cpu_write(pcp, val) __pcpu_size_call(this_cpu_write_, pcp, val)
                                     ^~~~~~~~~~~~~~~~
>> kernel/fork.c:183:3: note: in expansion of macro 'this_cpu_write'
      this_cpu_write(cached_stacks[i], NULL);
      ^~~~~~~~~~~~~~
>> arch/x86/include/asm/percpu.h:94:13: warning: assignment makes integer from pointer without a cast [-Wint-conversion]
      pto_tmp__ = (val);   \
                ^
   arch/x86/include/asm/percpu.h:418:36: note: in expansion of macro 'percpu_to_op'
    #define this_cpu_write_4(pcp, val) percpu_to_op("mov", (pcp), val)
                                       ^~~~~~~~~~~~
   include/linux/percpu-defs.h:366:11: note: in expansion of macro 'this_cpu_write_4'
      case 4: stem##4(variable, __VA_ARGS__);break;  \
              ^~~~
   include/linux/percpu-defs.h:495:34: note: in expansion of macro '__pcpu_size_call'
    #define this_cpu_write(pcp, val) __pcpu_size_call(this_cpu_write_, pcp, val)
                                     ^~~~~~~~~~~~~~~~
>> kernel/fork.c:183:3: note: in expansion of macro 'this_cpu_write'
      this_cpu_write(cached_stacks[i], NULL);
      ^~~~~~~~~~~~~~
   At top level:
   kernel/fork.c:173:12: warning: 'free_vm_stack_cache' defined but not used [-Wunused-function]
    static int free_vm_stack_cache(unsigned int cpu)
               ^~~~~~~~~~~~~~~~~~~

vim +/this_cpu_write +183 kernel/fork.c

   167	 * flush.  Try to minimize the number of calls by caching stacks.
   168	 */
   169	#define NR_CACHED_STACKS 2
   170	static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]);
   171	#endif
   172	
   173	static int free_vm_stack_cache(unsigned int cpu)
   174	{
   175		int i;
   176	
   177		for (i = 0; i < NR_CACHED_STACKS; i++) {
   178			struct vm_struct *vm_stack = this_cpu_read(cached_stacks[i]);
   179			if (!vm_stack)
   180				continue;
   181	
   182			vfree(vm_stack->addr);
 > 183			this_cpu_write(cached_stacks[i], NULL);
   184		}
   185	
   186		return 0;
   187	}
   188	
   189	static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
   190	{
   191	#ifdef CONFIG_VMAP_STACK

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

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