Re: [RFC PATCH 02/11] x86/preempt: Move preempt count to percpu hot section

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

Hi Brian,

[This is a private test report for your RFC patch.]
kernel test robot noticed the following build warnings:

[auto build test WARNING on 01157ddc58dc2fe428ec17dd5a18cc13f134639f]

url:    https://github.com/intel-lab-lkp/linux/commits/Brian-Gerst/percpu-Introduce-percpu-hot-section/20250223-031046
base:   01157ddc58dc2fe428ec17dd5a18cc13f134639f
patch link:    https://lore.kernel.org/r/20250222190623.262689-3-brgerst%40gmail.com
patch subject: [RFC PATCH 02/11] x86/preempt: Move preempt count to percpu hot section
config: i386-buildonly-randconfig-004-20250223 (https://download.01.org/0day-ci/archive/20250223/202502231946.RXtsMrTp-lkp@intel.com/config)
compiler: clang version 19.1.3 (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b254b6afab99)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250223/202502231946.RXtsMrTp-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/202502231946.RXtsMrTp-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from arch/x86/kernel/asm-offsets.c:9:
   In file included from include/linux/crypto.h:15:
   In file included from include/linux/completion.h:12:
   In file included from include/linux/swait.h:7:
   In file included from include/linux/spinlock.h:56:
>> include/linux/preempt.h:340:13: warning: declaration of 'struct task_struct' will not be visible outside of this function [-Wvisibility]
     340 |                           struct task_struct *next);
         |                                  ^
   1 warning generated.
--
   In file included from drivers/platform/surface/surface_hotplug.c:16:
   In file included from include/linux/acpi.h:13:
   In file included from include/linux/resource_ext.h:11:
   In file included from include/linux/slab.h:16:
   In file included from include/linux/gfp.h:7:
   In file included from include/linux/mmzone.h:8:
   In file included from include/linux/spinlock.h:56:
>> include/linux/preempt.h:340:13: warning: declaration of 'struct task_struct' will not be visible outside of this function [-Wvisibility]
     340 |                           struct task_struct *next);
         |                                  ^
   drivers/platform/surface/surface_hotplug.c:79:39: warning: arithmetic between different enumeration types ('enum shps_dsm_fn' and 'enum shps_irq_type') [-Wenum-enum-conversion]
      79 |         return SHPS_DSM_FN_IRQ_BASE_PRESENCE + type;
         |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~
   2 warnings generated.
--
   In file included from kernel/sched/core.c:10:
   In file included from include/linux/highmem.h:5:
   In file included from include/linux/fs.h:6:
   In file included from include/linux/wait_bit.h:8:
   In file included from include/linux/wait.h:9:
   In file included from include/linux/spinlock.h:56:
>> include/linux/preempt.h:340:13: warning: declaration of 'struct task_struct' will not be visible outside of this function [-Wvisibility]
     340 |                           struct task_struct *next);
         |                                  ^
   kernel/sched/core.c:4958:38: error: incompatible pointer types passing 'struct task_struct *' to parameter of type 'struct task_struct *' [-Werror,-Wincompatible-pointer-types]
    4958 |                 notifier->ops->sched_out(notifier, next);
         |                                                    ^~~~
   1 warning and 1 error generated.
--
   In file included from arch/x86/kernel/asm-offsets.c:9:
   In file included from include/linux/crypto.h:15:
   In file included from include/linux/completion.h:12:
   In file included from include/linux/swait.h:7:
   In file included from include/linux/spinlock.h:56:
>> include/linux/preempt.h:340:13: warning: declaration of 'struct task_struct' will not be visible outside of this function [-Wvisibility]
     340 |                           struct task_struct *next);
         |                                  ^
   1 warning generated.


vim +340 include/linux/preempt.h

e107be36efb2a23 Avi Kivity 2007-07-26  322  
e107be36efb2a23 Avi Kivity 2007-07-26  323  /**
e107be36efb2a23 Avi Kivity 2007-07-26  324   * preempt_ops - notifiers called when a task is preempted and rescheduled
e107be36efb2a23 Avi Kivity 2007-07-26  325   * @sched_in: we're about to be rescheduled:
e107be36efb2a23 Avi Kivity 2007-07-26  326   *    notifier: struct preempt_notifier for the task being scheduled
e107be36efb2a23 Avi Kivity 2007-07-26  327   *    cpu:  cpu we're scheduled on
e107be36efb2a23 Avi Kivity 2007-07-26  328   * @sched_out: we've just been preempted
e107be36efb2a23 Avi Kivity 2007-07-26  329   *    notifier: struct preempt_notifier for the task being preempted
e107be36efb2a23 Avi Kivity 2007-07-26  330   *    next: the task that's kicking us out
8592e6486a177a0 Tejun Heo  2009-12-02  331   *
8592e6486a177a0 Tejun Heo  2009-12-02  332   * Please note that sched_in and out are called under different
8592e6486a177a0 Tejun Heo  2009-12-02  333   * contexts.  sched_out is called with rq lock held and irq disabled
8592e6486a177a0 Tejun Heo  2009-12-02  334   * while sched_in is called without rq lock and irq enabled.  This
8592e6486a177a0 Tejun Heo  2009-12-02  335   * difference is intentional and depended upon by its users.
e107be36efb2a23 Avi Kivity 2007-07-26  336   */
e107be36efb2a23 Avi Kivity 2007-07-26  337  struct preempt_ops {
e107be36efb2a23 Avi Kivity 2007-07-26  338  	void (*sched_in)(struct preempt_notifier *notifier, int cpu);
e107be36efb2a23 Avi Kivity 2007-07-26  339  	void (*sched_out)(struct preempt_notifier *notifier,
e107be36efb2a23 Avi Kivity 2007-07-26 @340  			  struct task_struct *next);
e107be36efb2a23 Avi Kivity 2007-07-26  341  };
e107be36efb2a23 Avi Kivity 2007-07-26  342  

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