linux-kernel - Re: [PATCH] locking/qspinlock: Ensure node is initialised before updating prev->next

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Date:   Sat, 3 Feb 2018 10:24:38 +0800
From:   kbuild test robot <lkp@...el.com>
To:     Will Deacon <will.deacon@....com>
Cc:     kbuild-all@...org, linux-kernel@...r.kernel.org,
        Will Deacon <will.deacon@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] locking/qspinlock: Ensure node is initialised before
 updating prev->next

Hi Will,

I love your patch! Perhaps something to improve:

[auto build test WARNING on v4.15]
[cannot apply to tip/locking/core tip/core/locking tip/auto-latest next-20180202]
[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/Will-Deacon/locking-qspinlock-Ensure-node-is-initialised-before-updating-prev-next/20180203-095222
config: sparc64-allyesconfig (attached as .config)
compiler: sparc64-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=sparc64 

All warnings (new ones prefixed by >>):

   In file included from include/linux/kernel.h:10:0,
                    from include/linux/list.h:9,
                    from include/linux/smp.h:12,
                    from kernel/locking/qspinlock.c:25:
   kernel/locking/qspinlock.c: In function 'queued_spin_lock_slowpath':
   include/linux/compiler.h:264:8: error: conversion to non-scalar type requested
     union { typeof(x) __val; char __c[1]; } __u = \
           ^
>> arch/sparc/include/asm/barrier_64.h:45:2: note: in expansion of macro 'WRITE_ONCE'
     WRITE_ONCE(*p, v);      \
     ^~~~~~~~~~
   include/asm-generic/barrier.h:157:33: note: in expansion of macro '__smp_store_release'
    #define smp_store_release(p, v) __smp_store_release(p, v)
                                    ^~~~~~~~~~~~~~~~~~~
   kernel/locking/qspinlock.c:419:3: note: in expansion of macro 'smp_store_release'
      smp_store_release(prev->next, node);
      ^~~~~~~~~~~~~~~~~
--
   In file included from include/linux/kernel.h:10:0,
                    from include/linux/list.h:9,
                    from include/linux/smp.h:12,
                    from kernel//locking/qspinlock.c:25:
   kernel//locking/qspinlock.c: In function 'queued_spin_lock_slowpath':
   include/linux/compiler.h:264:8: error: conversion to non-scalar type requested
     union { typeof(x) __val; char __c[1]; } __u = \
           ^
>> arch/sparc/include/asm/barrier_64.h:45:2: note: in expansion of macro 'WRITE_ONCE'
     WRITE_ONCE(*p, v);      \
     ^~~~~~~~~~
   include/asm-generic/barrier.h:157:33: note: in expansion of macro '__smp_store_release'
    #define smp_store_release(p, v) __smp_store_release(p, v)
                                    ^~~~~~~~~~~~~~~~~~~
   kernel//locking/qspinlock.c:419:3: note: in expansion of macro 'smp_store_release'
      smp_store_release(prev->next, node);
      ^~~~~~~~~~~~~~~~~

vim +/WRITE_ONCE +45 arch/sparc/include/asm/barrier_64.h

d550bbd4 David Howells      2012-03-28  40  
45d9b859 Michael S. Tsirkin 2015-12-27  41  #define __smp_store_release(p, v)						\
47933ad4 Peter Zijlstra     2013-11-06  42  do {									\
47933ad4 Peter Zijlstra     2013-11-06  43  	compiletime_assert_atomic_type(*p);				\
47933ad4 Peter Zijlstra     2013-11-06  44  	barrier();							\
76695af2 Andrey Konovalov   2015-08-02 @45  	WRITE_ONCE(*p, v);						\
47933ad4 Peter Zijlstra     2013-11-06  46  } while (0)
47933ad4 Peter Zijlstra     2013-11-06  47  

:::::: The code at line 45 was first introduced by commit
:::::: 76695af20c015206cffb84b15912be6797d0cca2 locking, arch: use WRITE_ONCE()/READ_ONCE() in smp_store_release()/smp_load_acquire()

:::::: TO: Andrey Konovalov <andreyknvl@...gle.com>
:::::: CC: Ingo Molnar <mingo@...nel.org>

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