tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git preempt head: bafee3053cbbb524a19b093add8bd30fbb266001 commit: bc510815d5cad14f492e9a0033134655360365d3 [5/13] mm/pagemap: Clenaup PREEMPT_COUNT leftovers config: arm-randconfig-r011-20200913 (attached as .config) compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 3ed89b51da38f081fedb57727076262abb81d149) 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 arm cross compiling tool for clang build # apt-get install binutils-arm-linux-gnueabi git checkout bc510815d5cad14f492e9a0033134655360365d3 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All error/warnings (new ones prefixed by >>): In file included from fs/direct-io.c:30: VM_BUG_ON(preemptible()) ^ ; 1 error generated. -- In file included from fs/aio.c:21: In file included from include/linux/backing-dev.h:15: In file included from include/linux/blkdev.h:13: VM_BUG_ON(preemptible()) ^ ; In file included from fs/aio.c:29: include/linux/mman.h:138:9: warning: division by zero is undefined [-Wdivision-by-zero] _calc_vm_trans(flags, MAP_SYNC, VM_SYNC ); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/linux/mman.h:115:21: note: expanded from macro '_calc_vm_trans' : ((x) & (bit1)) / ((bit1) / (bit2)))) ^ ~~~~~~~~~~~~~~~~~ 1 warning and 1 error generated. -- In file included from fs/io_uring.c:61: In file included from include/linux/blkdev.h:13: VM_BUG_ON(preemptible()) ^ ; In file included from fs/io_uring.c:64: In file included from include/net/sock.h:46: In file included from include/linux/netdevice.h:37: In file included from include/linux/ethtool.h:18: In file included from include/uapi/linux/ethtool.h:19: In file included from include/linux/if_ether.h:19: In file included from include/linux/skbuff.h:31: include/linux/dma-mapping.h:632:9: warning: implicit conversion from 'unsigned long long' to 'unsigned long' changes value from 18446744073709551615 to 4294967295 [-Wconstant-conversion] return DMA_BIT_MASK(32); ~~~~~~ ^~~~~~~~~~~~~~~~ include/linux/dma-mapping.h:139:40: note: expanded from macro 'DMA_BIT_MASK' #define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1)) ^~~~~ 1 warning and 1 error generated. -- In file included from fs/pipe.c:22: VM_BUG_ON(preemptible()) ^ ; fs/pipe.c:760:15: warning: no previous prototype for function 'account_pipe_buffers' [-Wmissing-prototypes] unsigned long account_pipe_buffers(struct user_struct *user, ^ fs/pipe.c:760:1: note: declare 'static' if the function is not intended to be used outside of this translation unit unsigned long account_pipe_buffers(struct user_struct *user, ^ static fs/pipe.c:766:6: warning: no previous prototype for function 'too_many_pipe_buffers_soft' [-Wmissing-prototypes] bool too_many_pipe_buffers_soft(unsigned long user_bufs) ^ fs/pipe.c:766:1: note: declare 'static' if the function is not intended to be used outside of this translation unit bool too_many_pipe_buffers_soft(unsigned long user_bufs) ^ static fs/pipe.c:773:6: warning: no previous prototype for function 'too_many_pipe_buffers_hard' [-Wmissing-prototypes] bool too_many_pipe_buffers_hard(unsigned long user_bufs) ^ fs/pipe.c:773:1: note: declare 'static' if the function is not intended to be used outside of this translation unit bool too_many_pipe_buffers_hard(unsigned long user_bufs) ^ static fs/pipe.c:780:6: warning: no previous prototype for function 'pipe_is_unprivileged_user' [-Wmissing-prototypes] bool pipe_is_unprivileged_user(void) ^ fs/pipe.c:780:1: note: declare 'static' if the function is not intended to be used outside of this translation unit bool pipe_is_unprivileged_user(void) ^ static fs/pipe.c:1211:5: warning: no previous prototype for function 'pipe_resize_ring' [-Wmissing-prototypes] int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots) ^ fs/pipe.c:1211:1: note: declare 'static' if the function is not intended to be used outside of this translation unit int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots) ^ static 5 warnings and 1 error generated. -- In file included from fs/proc/meminfo.c:12: In file included from include/linux/swap.h:9: In file included from include/linux/memcontrol.h:22: In file included from include/linux/writeback.h:14: In file included from include/linux/blk-cgroup.h:23: In file included from include/linux/blkdev.h:13: VM_BUG_ON(preemptible()) ^ ; fs/proc/meminfo.c:22:28: warning: no previous prototype for function 'arch_report_meminfo' [-Wmissing-prototypes] void __attribute__((weak)) arch_report_meminfo(struct seq_file *m) ^ fs/proc/meminfo.c:22:1: note: declare 'static' if the function is not intended to be used outside of this translation unit void __attribute__((weak)) arch_report_meminfo(struct seq_file *m) ^ static 1 warning and 1 error generated. -- In file included from fs/kernfs/file.c:14: VM_BUG_ON(preemptible()) ^ ; fs/kernfs/file.c:127:15: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic] return NULL + !*ppos; ~~~~ ^ 1 warning and 1 error generated. -- In file included from fs/nfs/nfstrace.c:5: In file included from include/linux/nfs_fs.h:24: VM_BUG_ON(preemptible()) ^ ; In file included from fs/nfs/nfstrace.c:5: In file included from include/linux/nfs_fs.h:31: In file included from include/linux/sunrpc/auth.h:14: In file included from include/linux/sunrpc/msg_prot.h:202: In file included from include/linux/inet.h:42: In file included from include/net/net_namespace.h:39: In file included from include/linux/skbuff.h:31: include/linux/dma-mapping.h:632:9: warning: implicit conversion from 'unsigned long long' to 'unsigned long' changes value from 18446744073709551615 to 4294967295 [-Wconstant-conversion] return DMA_BIT_MASK(32); ~~~~~~ ^~~~~~~~~~~~~~~~ include/linux/dma-mapping.h:139:40: note: expanded from macro 'DMA_BIT_MASK' #define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1)) ^~~~~ In file included from fs/nfs/nfstrace.c:10: In file included from fs/nfs/nfstrace.h:1444: include/trace/define_trace.h:95:10: fatal error: './nfstrace.h' file not found #include TRACE_INCLUDE(TRACE_INCLUDE_FILE) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/trace/define_trace.h:90:32: note: expanded from macro 'TRACE_INCLUDE' # define TRACE_INCLUDE(system) __TRACE_INCLUDE(system) ^~~~~~~~~~~~~~~~~~~~~~~ include/trace/define_trace.h:87:34: note: expanded from macro '__TRACE_INCLUDE' # define __TRACE_INCLUDE(system) __stringify(TRACE_INCLUDE_PATH/system.h) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/linux/stringify.h:10:27: note: expanded from macro '__stringify' #define __stringify(x...) __stringify_1(x) ^~~~~~~~~~~~~~~~ include/linux/stringify.h:9:29: note: expanded from macro '__stringify_1' #define __stringify_1(x...) #x ^~ <scratch space>:80:1: note: expanded from here "./nfstrace.h" ^~~~~~~~~~~~~~ 1 warning and 2 errors generated. -- In file included from fs/nfs/nfs4trace.c:5: In file included from include/linux/nfs_fs.h:24: VM_BUG_ON(preemptible()) ^ ; In file included from fs/nfs/nfs4trace.c:5: In file included from include/linux/nfs_fs.h:31: In file included from include/linux/sunrpc/auth.h:14: In file included from include/linux/sunrpc/msg_prot.h:202: In file included from include/linux/inet.h:42: In file included from include/net/net_namespace.h:39: In file included from include/linux/skbuff.h:31: include/linux/dma-mapping.h:632:9: warning: implicit conversion from 'unsigned long long' to 'unsigned long' changes value from 18446744073709551615 to 4294967295 [-Wconstant-conversion] return DMA_BIT_MASK(32); ~~~~~~ ^~~~~~~~~~~~~~~~ include/linux/dma-mapping.h:139:40: note: expanded from macro 'DMA_BIT_MASK' #define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1)) ^~~~~ In file included from fs/nfs/nfs4trace.c:13: In file included from fs/nfs/nfs4trace.h:2308: include/trace/define_trace.h:95:10: fatal error: './nfs4trace.h' file not found #include TRACE_INCLUDE(TRACE_INCLUDE_FILE) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/trace/define_trace.h:90:32: note: expanded from macro 'TRACE_INCLUDE' # define TRACE_INCLUDE(system) __TRACE_INCLUDE(system) ^~~~~~~~~~~~~~~~~~~~~~~ include/trace/define_trace.h:87:34: note: expanded from macro '__TRACE_INCLUDE' # define __TRACE_INCLUDE(system) __stringify(TRACE_INCLUDE_PATH/system.h) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/linux/stringify.h:10:27: note: expanded from macro '__stringify' #define __stringify(x...) __stringify_1(x) ^~~~~~~~~~~~~~~~ include/linux/stringify.h:9:29: note: expanded from macro '__stringify_1' #define __stringify_1(x...) #x ^~ <scratch space>:9:1: note: expanded from here "./nfs4trace.h" ^~~~~~~~~~~~~~~ 1 warning and 2 errors generated. -- In file included from fs/gfs2/glock.c:12: In file included from include/linux/buffer_head.h:14: VM_BUG_ON(preemptible()) ^ ; In file included from fs/gfs2/glock.c:49: In file included from fs/gfs2/trace_gfs2.h:632: include/trace/define_trace.h:95:10: fatal error: './trace_gfs2.h' file not found #include TRACE_INCLUDE(TRACE_INCLUDE_FILE) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/trace/define_trace.h:90:32: note: expanded from macro 'TRACE_INCLUDE' # define TRACE_INCLUDE(system) __TRACE_INCLUDE(system) ^~~~~~~~~~~~~~~~~~~~~~~ include/trace/define_trace.h:87:34: note: expanded from macro '__TRACE_INCLUDE' # define __TRACE_INCLUDE(system) __stringify(TRACE_INCLUDE_PATH/system.h) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/linux/stringify.h:10:27: note: expanded from macro '__stringify' #define __stringify(x...) __stringify_1(x) ^~~~~~~~~~~~~~~~ include/linux/stringify.h:9:29: note: expanded from macro '__stringify_1' #define __stringify_1(x...) #x ^~ <scratch space>:14:1: note: expanded from here "./trace_gfs2.h" ^~~~~~~~~~~~~~~~ 2 errors generated. -- In file included from drivers/usb/host/ehci-platform.c:37: In file included from include/linux/usb/of.h:12: In file included from include/linux/usb/otg.h:13: In file included from include/linux/phy/phy.h:17: In file included from include/linux/regulator/consumer.h:35: In file included from include/linux/suspend.h:5: In file included from include/linux/swap.h:9: In file included from include/linux/memcontrol.h:22: In file included from include/linux/writeback.h:14: In file included from include/linux/blk-cgroup.h:23: In file included from include/linux/blkdev.h:13: VM_BUG_ON(preemptible()) ^ ; drivers/usb/host/ehci-platform.c:251:24: warning: shift count >= width of type [-Wshift-count-overflow] pdata->dma_mask_64 ? DMA_BIT_MASK(64) : DMA_BIT_MASK(32)); ^~~~~~~~~~~~~~~~ include/linux/dma-mapping.h:139:54: note: expanded from macro 'DMA_BIT_MASK' #define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1)) ^ ~~~ 1 warning and 1 error generated. -- In file included from drivers/usb/host/xhci-plat.c:21: In file included from include/linux/usb/of.h:12: In file included from include/linux/usb/otg.h:13: In file included from include/linux/phy/phy.h:17: In file included from include/linux/regulator/consumer.h:35: In file included from include/linux/suspend.h:5: In file included from include/linux/swap.h:9: In file included from include/linux/memcontrol.h:22: In file included from include/linux/writeback.h:14: In file included from include/linux/blk-cgroup.h:23: In file included from include/linux/blkdev.h:13: VM_BUG_ON(preemptible()) ^ ; DMA_BIT_MASK(64)); ^~~~~~~~~~~~~~~~ include/linux/dma-mapping.h:139:54: note: expanded from macro 'DMA_BIT_MASK' #define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1)) ^ ~~~ drivers/usb/host/xhci-plat.c:212:43: warning: shift count >= width of type [-Wshift-count-overflow] ret = dma_set_mask_and_coherent(sysdev, DMA_BIT_MASK(64)); ^~~~~~~~~~~~~~~~ include/linux/dma-mapping.h:139:54: note: expanded from macro 'DMA_BIT_MASK' #define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1)) ^ ~~~ 2 warnings and 1 error generated. .. # https://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git/commit/?id... git remote add tglx-devel https://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git git fetch --no-tags tglx-devel preempt git checkout bc510815d5cad14f492e9a0033134655360365d3 vim +171 include/linux/pagemap.h 123 124 /* 125 * speculatively take a reference to a page. 126 * If the page is free (_refcount == 0), then _refcount is untouched, and 0 127 * is returned. Otherwise, _refcount is incremented by 1 and 1 is returned. 128 * 129 * This function must be called inside the same rcu_read_lock() section as has 130 * been used to lookup the page in the pagecache radix-tree (or page table): 131 * this allows allocators to use a synchronize_rcu() to stabilize _refcount. 132 * 133 * Unless an RCU grace period has passed, the count of all pages coming out 134 * of the allocator must be considered unstable. page_count may return higher 135 * than expected, and put_page must be able to do the right thing when the 136 * page has been finished with, no matter what it is subsequently allocated 137 * for (because put_page is what is used here to drop an invalid speculative 138 * reference). 139 * 140 * This is the interesting part of the lockless pagecache (and lockless 141 * get_user_pages) locking protocol, where the lookup-side (eg. find_get_page) 142 * has the following pattern: 143 * 1. find page in radix tree 144 * 2. conditionally increment refcount 145 * 3. check the page is still in pagecache (if no, goto 1) 146 * 147 * Remove-side that cares about stability of _refcount (eg. reclaim) has the 148 * following (with the i_pages lock held): 149 * A. atomically check refcount is correct and set it to 0 (atomic_cmpxchg) 150 * B. remove page from pagecache 151 * C. free the page 152 * 153 * There are 2 critical interleavings that matter: 154 * - 2 runs before A: in this case, A sees elevated refcount and bails out 155 * - A runs before 2: in this case, 2 sees zero refcount and retries; 156 * subsequently, B will complete and 1 will find no page, causing the 157 * lookup to return NULL. 158 * 159 * It is possible that between 1 and 2, the page is removed then the exact same 160 * page is inserted into the same position in pagecache. That's OK: the 161 * old find_get_page using a lock could equally have run before or after 162 * such a re-insertion, depending on order that locks are granted. 163 * 164 * Lookups racing against pagecache insertion isn't a big problem: either 1 165 * will find the page or it will not. Likewise, the old find_get_page could run 166 * either before the insertion or afterwards, depending on timing. 167 */ 168 static inline int __page_cache_add_speculative(struct page *page, int count) 169 { 170 #ifdef CONFIG_TINY_RCU 172 /* 173 * Preempt must be disabled here - we rely on rcu_read_lock doing 174 * this for us. 175 * 176 * Pagecache won't be truncated from interrupt context, so if we have 177 * found a page in the radix tree here, we have pinned its refcount by 178 * disabling preempt, and hence no need for the "speculative get" that 179 * SMP requires. 180 */ 181 VM_BUG_ON_PAGE(page_count(page) == 0, page); 182 page_ref_add(page, count); 183 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org