linux-kernel - [tip:locking/core 9/11] include/asm-generic/atomic-instrumented.h:288:24: sparse: cast truncates bits from constant value (100 becomes 0)

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Date:   Mon, 12 Mar 2018 22:52:21 +0800
From:   kbuild test robot <fengguang.wu@...el.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     kbuild-all@...org, linux-kernel@...r.kernel.org,
        tipbuild@...or.com, Ingo Molnar <mingo@...nel.org>
Subject: [tip:locking/core 9/11]
 include/asm-generic/atomic-instrumented.h:288:24: sparse: cast truncates
 bits from constant value (100 becomes 0)

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking/core
head:   ac605bee0bfab40fd5d11964705e907d2d5a32de
commit: 8bf705d130396e69c04cd8e6e010244ad2ce71f4 [9/11] locking/atomic/x86: Switch atomic.h to use atomic-instrumented.h
reproduce:
        # apt-get install sparse
        git checkout 8bf705d130396e69c04cd8e6e010244ad2ce71f4
        make ARCH=x86_64 allmodconfig
        make C=1 CF=-D__CHECK_ENDIAN__


sparse warnings: (new ones prefixed by >>)

   kernel/locking/qspinlock.c:418:22: sparse: incorrect type in assignment (different modifiers) @@    expected struct mcs_spinlock *prev @@    got struct struct mcs_spinlock *prev @@
   kernel/locking/qspinlock.c:418:22:    expected struct mcs_spinlock *prev
   kernel/locking/qspinlock.c:418:22:    got struct mcs_spinlock [pure] *
   kernel/locking/qspinlock_paravirt.h:519:1: sparse: symbol '__pv_queued_spin_unlock_slowpath' was not declared. Should it be static?
   kernel/locking/qspinlock.c:418:22: sparse: incorrect type in assignment (different modifiers) @@    expected struct mcs_spinlock *prev @@    got struct struct mcs_spinlock *prev @@
   kernel/locking/qspinlock.c:418:22:    expected struct mcs_spinlock *prev
   kernel/locking/qspinlock.c:418:22:    got struct mcs_spinlock [pure] *
>> include/asm-generic/atomic-instrumented.h:288:24: sparse: cast truncates bits from constant value (100 becomes 0)

vim +288 include/asm-generic/atomic-instrumented.h

b06ed71a6 Dmitry Vyukov 2018-01-29  282  
b06ed71a6 Dmitry Vyukov 2018-01-29  283  static __always_inline unsigned long
b06ed71a6 Dmitry Vyukov 2018-01-29  284  cmpxchg_size(volatile void *ptr, unsigned long old, unsigned long new, int size)
b06ed71a6 Dmitry Vyukov 2018-01-29  285  {
b06ed71a6 Dmitry Vyukov 2018-01-29  286  	switch (size) {
b06ed71a6 Dmitry Vyukov 2018-01-29  287  	case 1:
b06ed71a6 Dmitry Vyukov 2018-01-29 @288  		return arch_cmpxchg((u8 *)ptr, (u8)old, (u8)new);
b06ed71a6 Dmitry Vyukov 2018-01-29  289  	case 2:
b06ed71a6 Dmitry Vyukov 2018-01-29  290  		return arch_cmpxchg((u16 *)ptr, (u16)old, (u16)new);
b06ed71a6 Dmitry Vyukov 2018-01-29  291  	case 4:
b06ed71a6 Dmitry Vyukov 2018-01-29  292  		return arch_cmpxchg((u32 *)ptr, (u32)old, (u32)new);
b06ed71a6 Dmitry Vyukov 2018-01-29  293  	case 8:
b06ed71a6 Dmitry Vyukov 2018-01-29  294  		BUILD_BUG_ON(sizeof(unsigned long) != 8);
b06ed71a6 Dmitry Vyukov 2018-01-29  295  		return arch_cmpxchg((u64 *)ptr, (u64)old, (u64)new);
b06ed71a6 Dmitry Vyukov 2018-01-29  296  	}
b06ed71a6 Dmitry Vyukov 2018-01-29  297  	BUILD_BUG();
b06ed71a6 Dmitry Vyukov 2018-01-29  298  	return 0;
b06ed71a6 Dmitry Vyukov 2018-01-29  299  }
b06ed71a6 Dmitry Vyukov 2018-01-29  300  

:::::: The code at line 288 was first introduced by commit
:::::: b06ed71a624ba088a3e3e3ac7d4185f48c7c1660 locking/atomic, asm-generic: Add asm-generic/atomic-instrumented.h

:::::: TO: Dmitry Vyukov <dvyukov@...gle.com>
:::::: CC: Ingo Molnar <mingo@...nel.org>

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