Hi Tetsuo,

I love your patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v4.19 next-20181102]
[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/Tetsuo-Handa/printk-Add-line-buffered-printk-API/20181103-010234
config: i386-randconfig-x002-201843 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   In file included from kernel/printk/printk_buffered.c:5:0:
>> kernel/printk/internal.h:28:8: error: unknown type name 'raw_spinlock_t'
    extern raw_spinlock_t logbuf_lock;
           ^~~~~~~~~~~~~~

vim +/raw_spinlock_t +28 kernel/printk/internal.h

f956d1a3 Tetsuo Handa       2018-11-02  27  
099f1c84 Sergey Senozhatsky 2016-12-27 @28  extern raw_spinlock_t logbuf_lock;
099f1c84 Sergey Senozhatsky 2016-12-27  29  

:::::: The code at line 28 was first introduced by commit
:::::: 099f1c84c0052ec1b27f1c3942eed5830d86bdbb printk: introduce per-cpu safe_print seq buffer

:::::: TO: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
:::::: CC: Petr Mladek <pmladek@suse.com>

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