Re: [PATCH printk v3 14/15] printk: extend console_lock for proper kthread support

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

Hi John,

I love your patch! Perhaps something to improve:

[auto build test WARNING on 84d7df104dbab9c3dda8f2c5b46f9a6fc256fe02]

url:    https://github.com/intel-lab-lkp/linux/commits/John-Ogness/printk-for-next/20220420-080725
base:   84d7df104dbab9c3dda8f2c5b46f9a6fc256fe02
config: s390-randconfig-r032-20220419 (https://download.01.org/0day-ci/archive/20220420/202204201103.MeWPs1iv-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project bac6cd5bf85669e3376610cfc4c4f9ca015e7b9b)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install s390 cross compiling tool for clang build
        # apt-get install binutils-s390x-linux-gnu
        # https://github.com/intel-lab-lkp/linux/commit/5139c5b347088e124f3812a3fa63eb284b14f2dc
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review John-Ogness/printk-for-next/20220420-080725
        git checkout 5139c5b347088e124f3812a3fa63eb284b14f2dc
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash kernel/printk/

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 >>):

   In file included from kernel/printk/printk.c:35:
   In file included from include/linux/memblock.h:13:
   In file included from arch/s390/include/asm/dma.h:5:
   In file included from arch/s390/include/asm/io.h:75:
   include/asm-generic/io.h:464:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __raw_readb(PCI_IOBASE + addr);
                             ~~~~~~~~~~ ^
   include/asm-generic/io.h:477:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/big_endian.h:37:59: note: expanded from macro '__le16_to_cpu'
   #define __le16_to_cpu(x) __swab16((__force __u16)(__le16)(x))
                                                             ^
   include/uapi/linux/swab.h:102:54: note: expanded from macro '__swab16'
   #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x))
                                                        ^
   In file included from kernel/printk/printk.c:35:
   In file included from include/linux/memblock.h:13:
   In file included from arch/s390/include/asm/dma.h:5:
   In file included from arch/s390/include/asm/io.h:75:
   include/asm-generic/io.h:490:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
                                                           ~~~~~~~~~~ ^
   include/uapi/linux/byteorder/big_endian.h:35:59: note: expanded from macro '__le32_to_cpu'
   #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
                                                             ^
   include/uapi/linux/swab.h:115:54: note: expanded from macro '__swab32'
   #define __swab32(x) (__u32)__builtin_bswap32((__u32)(x))
                                                        ^
   In file included from kernel/printk/printk.c:35:
   In file included from include/linux/memblock.h:13:
   In file included from arch/s390/include/asm/dma.h:5:
   In file included from arch/s390/include/asm/io.h:75:
   include/asm-generic/io.h:501:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writeb(value, PCI_IOBASE + addr);
                               ~~~~~~~~~~ ^
   include/asm-generic/io.h:511:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   include/asm-generic/io.h:521:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
                                                         ~~~~~~~~~~ ^
   include/asm-generic/io.h:609:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           readsb(PCI_IOBASE + addr, buffer, count);
                  ~~~~~~~~~~ ^
   include/asm-generic/io.h:617:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           readsw(PCI_IOBASE + addr, buffer, count);
                  ~~~~~~~~~~ ^
   include/asm-generic/io.h:625:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           readsl(PCI_IOBASE + addr, buffer, count);
                  ~~~~~~~~~~ ^
   include/asm-generic/io.h:634:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           writesb(PCI_IOBASE + addr, buffer, count);
                   ~~~~~~~~~~ ^
   include/asm-generic/io.h:643:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           writesw(PCI_IOBASE + addr, buffer, count);
                   ~~~~~~~~~~ ^
   include/asm-generic/io.h:652:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
           writesl(PCI_IOBASE + addr, buffer, count);
                   ~~~~~~~~~~ ^
>> kernel/printk/printk.c:2703:6: warning: no previous prototype for function 'console_lock_single_hold' [-Wmissing-prototypes]
   void console_lock_single_hold(struct console *con)
        ^
   kernel/printk/printk.c:2703:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   void console_lock_single_hold(struct console *con)
   ^
   static 
   13 warnings generated.


vim +/console_lock_single_hold +2703 kernel/printk/printk.c

  2697	
  2698	/*
  2699	 * Lock the console_lock, but rather than blocking all the kthread printers,
  2700	 * lock a specified kthread printer and hold the lock. This is useful if
  2701	 * console flags for a particular console need to be updated.
  2702	 */
> 2703	void console_lock_single_hold(struct console *con)
  2704	{
  2705		might_sleep();
  2706		down_console_sem();
  2707		mutex_lock(&con->lock);
  2708		console_locked = 1;
  2709		console_may_schedule = 1;
  2710	}
  2711	

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