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* [linux-rt-devel:linux-5.14.y-rt-rebase 184/245] mm/vmalloc.c:1887:2: warning: Value stored to 'cpu' is never read [clang-analyzer-deadcode.DeadStores]
@ 2021-08-16 23:48 kernel test robot
  0 siblings, 0 replies; only message in thread
From: kernel test robot @ 2021-08-16 23:48 UTC (permalink / raw)
  To: Thomas Gleixner
  Cc: clang-built-linux, kbuild-all, linux-kernel, Sebastian Andrzej Siewior

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tree:   https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-5.14.y-rt-rebase
head:   0eead4e5a60cb716ec911a552787a69332cf6943
commit: 9584df5e521f3b4e0a2063d7878762f7aa54fca5 [184/245] mm/vmalloc: Another preempt disable region which sucks
config: riscv-randconfig-c006-20210816 (attached as .config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 44d0a99a12ec7ead4d2f5ef649ba05b40f6d463d)
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 riscv cross compiling tool for clang build
        # apt-get install binutils-riscv64-linux-gnu
        # https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/commit/?id=9584df5e521f3b4e0a2063d7878762f7aa54fca5
        git remote add linux-rt-devel https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
        git fetch --no-tags linux-rt-devel linux-5.14.y-rt-rebase
        git checkout 9584df5e521f3b4e0a2063d7878762f7aa54fca5
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=riscv clang-analyzer 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>


clang-analyzer warnings: (new ones prefixed by >>)
           ^~~~~
   include/asm-generic/bitops/fls.h:17:6: note: Assuming 'x' is not equal to 0, which participates in a condition later
           if (!x)
               ^~
   include/asm-generic/bitops/fls.h:17:2: note: Taking false branch
           if (!x)
           ^
   include/asm-generic/bitops/fls.h:19:6: note: Assuming the condition is false
           if (!(x & 0xffff0000u)) {
               ^~~~~~~~~~~~~~~~~~
   include/asm-generic/bitops/fls.h:19:2: note: Taking false branch
           if (!(x & 0xffff0000u)) {
           ^
   include/asm-generic/bitops/fls.h:23:6: note: Assuming the condition is false
           if (!(x & 0xff000000u)) {
               ^~~~~~~~~~~~~~~~~~
   include/asm-generic/bitops/fls.h:23:2: note: Taking false branch
           if (!(x & 0xff000000u)) {
           ^
   include/asm-generic/bitops/fls.h:27:6: note: Assuming the condition is false
           if (!(x & 0xf0000000u)) {
               ^~~~~~~~~~~~~~~~~~
   include/asm-generic/bitops/fls.h:27:2: note: Taking false branch
           if (!(x & 0xf0000000u)) {
           ^
   include/asm-generic/bitops/fls.h:31:6: note: Assuming the condition is false
           if (!(x & 0xc0000000u)) {
               ^~~~~~~~~~~~~~~~~~
   include/asm-generic/bitops/fls.h:31:2: note: Taking false branch
           if (!(x & 0xc0000000u)) {
           ^
   include/asm-generic/bitops/fls.h:35:6: note: Assuming the condition is false
           if (!(x & 0x80000000u)) {
               ^~~~~~~~~~~~~~~~~~
   include/asm-generic/bitops/fls.h:35:2: note: Taking false branch
           if (!(x & 0x80000000u)) {
           ^
   include/asm-generic/bitops/fls.h:39:2: note: Returning the value 32 (loaded from 'r')
           return r;
           ^~~~~~~~
   include/linux/bitops.h:188:10: note: Returning from 'fls'
                   return fls(l);
                          ^~~~~~
   include/linux/bitops.h:188:3: note: Returning the value 32
                   return fls(l);
                   ^~~~~~~~~~~~~
   include/linux/log2.h:57:16: note: Returning from 'fls_long'
           return 1UL << fls_long(n - 1);
                         ^~~~~~~~~~~~~~~
   include/linux/log2.h:57:13: note: The result of the left shift is undefined due to shifting by '32', which is greater or equal to the width of type 'unsigned long'
           return 1UL << fls_long(n - 1);
                      ^  ~~~~~~~~~~~~~~~
   Suppressed 14 warnings (14 in non-user code).
   Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
   9 warnings generated.
   Suppressed 9 warnings (9 in non-user code).
   Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
   9 warnings generated.
   Suppressed 9 warnings (9 in non-user code).
   Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
   9 warnings generated.
   Suppressed 9 warnings (9 in non-user code).
   Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
   9 warnings generated.
   Suppressed 9 warnings (9 in non-user code).
   Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
   9 warnings generated.
   Suppressed 9 warnings (9 in non-user code).
   Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
   9 warnings generated.
   Suppressed 9 warnings (9 in non-user code).
   Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
   8 warnings generated.
   Suppressed 8 warnings (8 in non-user code).
   Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
   9 warnings generated.
   Suppressed 9 warnings (9 in non-user code).
   Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
   8 warnings generated.
   Suppressed 8 warnings (8 in non-user code).
   Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
   9 warnings generated.
   Suppressed 9 warnings (9 in non-user code).
   Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
   9 warnings generated.
   Suppressed 9 warnings (9 in non-user code).
   Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
   17 warnings generated.
   mm/vmalloc.c:285:2: warning: Value stored to 'start' is never read [clang-analyzer-deadcode.DeadStores]
           start = addr;
           ^       ~~~~
   mm/vmalloc.c:285:2: note: Value stored to 'start' is never read
           start = addr;
           ^       ~~~~
   mm/vmalloc.c:568:18: warning: Value stored to 'nr' during its initialization is never read [clang-analyzer-deadcode.DeadStores]
           unsigned int i, nr = (end - addr) >> PAGE_SHIFT;
                           ^~   ~~~~~~~~~~~~~~~~~~~~~~~~~~
   mm/vmalloc.c:568:18: note: Value stored to 'nr' during its initialization is never read
           unsigned int i, nr = (end - addr) >> PAGE_SHIFT;
                           ^~   ~~~~~~~~~~~~~~~~~~~~~~~~~~
>> mm/vmalloc.c:1887:2: warning: Value stored to 'cpu' is never read [clang-analyzer-deadcode.DeadStores]
           cpu = get_cpu_light();
           ^
   mm/vmalloc.c:1887:2: note: Value stored to 'cpu' is never read
   mm/vmalloc.c:1972:2: warning: Value stored to 'cpu' is never read [clang-analyzer-deadcode.DeadStores]
           cpu = get_cpu_light();
           ^
   mm/vmalloc.c:1972:2: note: Value stored to 'cpu' is never read
   mm/vmalloc.c:1978:23: warning: The result of the left shift is undefined due to shifting by '32', which is greater or equal to the width of type 'unsigned long' [clang-analyzer-core.UndefinedBinaryOperatorResult]
                   if (vb->free < (1UL << order)) {
                                       ^  ~~~~~
   mm/vmalloc.c:1959:2: note: Assuming the condition is true
           BUG_ON(offset_in_page(size));
           ^
   include/asm-generic/bug.h:65:36: note: expanded from macro 'BUG_ON'
   #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
                                      ^~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:78:40: note: expanded from macro 'unlikely'
   # define unlikely(x)    __builtin_expect(!!(x), 0)
                                             ^~~~
   mm/vmalloc.c:1959:2: note: Taking false branch
           BUG_ON(offset_in_page(size));
           ^
   include/asm-generic/bug.h:65:32: note: expanded from macro 'BUG_ON'
   #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
                                  ^
   mm/vmalloc.c:1959:2: note: Loop condition is false.  Exiting loop
           BUG_ON(offset_in_page(size));
           ^
   include/asm-generic/bug.h:65:27: note: expanded from macro 'BUG_ON'
   #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
                             ^
   mm/vmalloc.c:1960:9: note: Assuming the condition is false
           BUG_ON(size > PAGE_SIZE*VMAP_MAX_ALLOC);
                  ^
   include/asm-generic/bug.h:65:45: note: expanded from macro 'BUG_ON'
   #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
                                      ~~~~~~~~~^~~~~~~~~~
   include/linux/compiler.h:78:42: note: expanded from macro 'unlikely'
   # define unlikely(x)    __builtin_expect(!!(x), 0)
                                               ^
   mm/vmalloc.c:1960:2: note: Taking false branch
           BUG_ON(size > PAGE_SIZE*VMAP_MAX_ALLOC);
           ^
   include/asm-generic/bug.h:65:32: note: expanded from macro 'BUG_ON'
   #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
                                  ^
   mm/vmalloc.c:1960:2: note: Loop condition is false.  Exiting loop
           BUG_ON(size > PAGE_SIZE*VMAP_MAX_ALLOC);
           ^
   include/asm-generic/bug.h:65:27: note: expanded from macro 'BUG_ON'
   #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while (0)
                             ^
   mm/vmalloc.c:1961:14: note: Assuming 'size' is not equal to 0
           if (WARN_ON(size == 0)) {
                       ^
   include/asm-generic/bug.h:121:25: note: expanded from macro 'WARN_ON'
           int __ret_warn_on = !!(condition);                              \
                                  ^~~~~~~~~
   mm/vmalloc.c:1961:6: note: Taking false branch
           if (WARN_ON(size == 0)) {
               ^
   include/asm-generic/bug.h:122:2: note: expanded from macro 'WARN_ON'
           if (unlikely(__ret_warn_on))                                    \
           ^
   mm/vmalloc.c:1961:2: note: Taking false branch
           if (WARN_ON(size == 0)) {
           ^
   mm/vmalloc.c:1969:10: note: Calling 'get_order'
           order = get_order(size);
                   ^~~~~~~~~~~~~~~
   include/asm-generic/getorder.h:31:2: note: Taking false branch
           if (__builtin_constant_p(size)) {
           ^
   include/asm-generic/getorder.h:44:9: note: Calling 'fls'
           return fls(size);
                  ^~~~~~~~~
   include/asm-generic/bitops/fls.h:15:2: note: 'r' initialized to 32
           int r = 32;
           ^~~~~
   include/asm-generic/bitops/fls.h:17:6: note: Assuming 'x' is not equal to 0, which participates in a condition later
           if (!x)
               ^~
   include/asm-generic/bitops/fls.h:17:2: note: Taking false branch
           if (!x)
           ^
   include/asm-generic/bitops/fls.h:19:6: note: Assuming the condition is false
           if (!(x & 0xffff0000u)) {
               ^~~~~~~~~~~~~~~~~~
   include/asm-generic/bitops/fls.h:19:2: note: Taking false branch
           if (!(x & 0xffff0000u)) {
           ^
   include/asm-generic/bitops/fls.h:23:6: note: Assuming the condition is false
           if (!(x & 0xff000000u)) {
               ^~~~~~~~~~~~~~~~~~
   include/asm-generic/bitops/fls.h:23:2: note: Taking false branch
           if (!(x & 0xff000000u)) {
           ^
   include/asm-generic/bitops/fls.h:27:6: note: Assuming the condition is false
           if (!(x & 0xf0000000u)) {
               ^~~~~~~~~~~~~~~~~~

vim +/cpu +1887 mm/vmalloc.c

  1835	
  1836	/**
  1837	 * new_vmap_block - allocates new vmap_block and occupies 2^order pages in this
  1838	 *                  block. Of course pages number can't exceed VMAP_BBMAP_BITS
  1839	 * @order:    how many 2^order pages should be occupied in newly allocated block
  1840	 * @gfp_mask: flags for the page level allocator
  1841	 *
  1842	 * Return: virtual address in a newly allocated block or ERR_PTR(-errno)
  1843	 */
  1844	static void *new_vmap_block(unsigned int order, gfp_t gfp_mask)
  1845	{
  1846		struct vmap_block_queue *vbq;
  1847		struct vmap_block *vb;
  1848		struct vmap_area *va;
  1849		unsigned long vb_idx;
  1850		int node, err, cpu;
  1851		void *vaddr;
  1852	
  1853		node = numa_node_id();
  1854	
  1855		vb = kmalloc_node(sizeof(struct vmap_block),
  1856				gfp_mask & GFP_RECLAIM_MASK, node);
  1857		if (unlikely(!vb))
  1858			return ERR_PTR(-ENOMEM);
  1859	
  1860		va = alloc_vmap_area(VMAP_BLOCK_SIZE, VMAP_BLOCK_SIZE,
  1861						VMALLOC_START, VMALLOC_END,
  1862						node, gfp_mask);
  1863		if (IS_ERR(va)) {
  1864			kfree(vb);
  1865			return ERR_CAST(va);
  1866		}
  1867	
  1868		vaddr = vmap_block_vaddr(va->va_start, 0);
  1869		spin_lock_init(&vb->lock);
  1870		vb->va = va;
  1871		/* At least something should be left free */
  1872		BUG_ON(VMAP_BBMAP_BITS <= (1UL << order));
  1873		vb->free = VMAP_BBMAP_BITS - (1UL << order);
  1874		vb->dirty = 0;
  1875		vb->dirty_min = VMAP_BBMAP_BITS;
  1876		vb->dirty_max = 0;
  1877		INIT_LIST_HEAD(&vb->free_list);
  1878	
  1879		vb_idx = addr_to_vb_idx(va->va_start);
  1880		err = xa_insert(&vmap_blocks, vb_idx, vb, gfp_mask);
  1881		if (err) {
  1882			kfree(vb);
  1883			free_vmap_area(va);
  1884			return ERR_PTR(err);
  1885		}
  1886	
> 1887		cpu = get_cpu_light();
  1888		vbq = this_cpu_ptr(&vmap_block_queue);
  1889		spin_lock(&vbq->lock);
  1890		list_add_tail_rcu(&vb->free_list, &vbq->free);
  1891		spin_unlock(&vbq->lock);
  1892		put_cpu_light();
  1893	
  1894		return vaddr;
  1895	}
  1896	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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2021-08-16 23:48 [linux-rt-devel:linux-5.14.y-rt-rebase 184/245] mm/vmalloc.c:1887:2: warning: Value stored to 'cpu' is never read [clang-analyzer-deadcode.DeadStores] kernel test robot

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