Hi Thomas, I love your patch! Yet something to improve: [auto build test ERROR on drm-intel/for-linux-next] [also build test ERROR on linus/master v5.9-rc5 next-20200914] [cannot apply to rcu/dev arm/for-next tip/sched/core linux/master] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch] url: https://github.com/0day-ci/linux/commits/Thomas-Gleixner/preempt-Make-preempt-count-unconditional/20200915-044640 base: git://anongit.freedesktop.org/drm-intel for-linux-next config: arm-randconfig-r002-20200914 (attached as .config) compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project b2c32c90bab09a6e2c1f370429db26017a182143) 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 # 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@xxxxxxxxx> All error/warnings (new ones prefixed by >>): In file included from drivers/scsi/scsi.c:47: In file included from include/linux/blkdev.h:13: >> include/linux/pagemap.h:181:2: error: called object type 'void' is not a function or function pointer VM_BUG_ON_PAGE(page_count(page) == 0, page); ^ include/linux/mmdebug.h:46:36: note: expanded from macro 'VM_BUG_ON_PAGE' #define VM_BUG_ON_PAGE(cond, page) VM_BUG_ON(cond) ^ include/linux/mmdebug.h:45:25: note: expanded from macro 'VM_BUG_ON' #define VM_BUG_ON(cond) BUILD_BUG_ON_INVALID(cond) ^ include/linux/build_bug.h:30:33: note: expanded from macro 'BUILD_BUG_ON_INVALID' #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e)))) ^ In file included from drivers/scsi/scsi.c:62: In file included from include/scsi/scsi_cmnd.h:5: 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 drivers/scsi/scsicam.c:19: In file included from include/linux/blkdev.h:13: >> include/linux/pagemap.h:181:2: error: called object type 'void' is not a function or function pointer VM_BUG_ON_PAGE(page_count(page) == 0, page); ^ include/linux/mmdebug.h:46:36: note: expanded from macro 'VM_BUG_ON_PAGE' #define VM_BUG_ON_PAGE(cond, page) VM_BUG_ON(cond) ^ include/linux/mmdebug.h:45:25: note: expanded from macro 'VM_BUG_ON' #define VM_BUG_ON(cond) BUILD_BUG_ON_INVALID(cond) ^ include/linux/build_bug.h:30:33: note: expanded from macro 'BUILD_BUG_ON_INVALID' #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e)))) ^ 1 error generated. -- In file included from drivers/scsi/scsi_sysfs.c:13: In file included from include/linux/blkdev.h:13: >> include/linux/pagemap.h:181:2: error: called object type 'void' is not a function or function pointer VM_BUG_ON_PAGE(page_count(page) == 0, page); ^ include/linux/mmdebug.h:46:36: note: expanded from macro 'VM_BUG_ON_PAGE' #define VM_BUG_ON_PAGE(cond, page) VM_BUG_ON(cond) ^ include/linux/mmdebug.h:45:25: note: expanded from macro 'VM_BUG_ON' #define VM_BUG_ON(cond) BUILD_BUG_ON_INVALID(cond) ^ include/linux/build_bug.h:30:33: note: expanded from macro 'BUILD_BUG_ON_INVALID' #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e)))) ^ In file included from drivers/scsi/scsi_sysfs.c:20: In file included from include/scsi/scsi_tcq.h:6: In file included from include/scsi/scsi_cmnd.h:5: 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)) ^~~~~ drivers/scsi/scsi_sysfs.c:373:1: warning: format specifies type 'short' but the argument has type 'int' [-Wformat] shost_rd_attr(can_queue, "%hd\n"); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ %d drivers/scsi/scsi_sysfs.c:176:45: note: expanded from macro 'shost_rd_attr' #define shost_rd_attr(field, format_string) \ ^ drivers/scsi/scsi_sysfs.c:173:2: note: expanded from macro '\ shost_rd_attr2' shost_show_function(name, field, format_string) \ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/scsi/scsi_sysfs.c:165:43: note: expanded from macro 'shost_show_function' return snprintf (buf, 20, format_string, shost->field); \ ~~~~~~~~~~~~~ ^~~~~~~~~~~~ 2 warnings and 1 error generated. -- In file included from drivers/scsi/ufs/ufshcd.c:18: In file included from drivers/scsi/ufs/ufshcd.h:32: 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: >> include/linux/pagemap.h:181:2: error: called object type 'void' is not a function or function pointer VM_BUG_ON_PAGE(page_count(page) == 0, page); ^ include/linux/mmdebug.h:46:36: note: expanded from macro 'VM_BUG_ON_PAGE' #define VM_BUG_ON_PAGE(cond, page) VM_BUG_ON(cond) ^ include/linux/mmdebug.h:45:25: note: expanded from macro 'VM_BUG_ON' #define VM_BUG_ON(cond) BUILD_BUG_ON_INVALID(cond) ^ include/linux/build_bug.h:30:33: note: expanded from macro 'BUILD_BUG_ON_INVALID' #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e)))) ^ In file included from drivers/scsi/ufs/ufshcd.c:18: In file included from drivers/scsi/ufs/ufshcd.h:41: In file included from include/scsi/scsi_cmnd.h:5: 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)) ^~~~~ >> drivers/scsi/ufs/ufshcd.c:8716:44: warning: shift count >= width of type [-Wshift-count-overflow] if (!dma_set_mask_and_coherent(hba->dev, 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. -- In file included from drivers/scsi/hisi_sas/hisi_sas_main.c:7: In file included from drivers/scsi/hisi_sas/hisi_sas.h:16: In file included from include/linux/libata.h:21: In file included from include/scsi/scsi_host.h:11: In file included from include/linux/blk-mq.h:5: In file included from include/linux/blkdev.h:13: >> include/linux/pagemap.h:181:2: error: called object type 'void' is not a function or function pointer VM_BUG_ON_PAGE(page_count(page) == 0, page); ^ include/linux/mmdebug.h:46:36: note: expanded from macro 'VM_BUG_ON_PAGE' #define VM_BUG_ON_PAGE(cond, page) VM_BUG_ON(cond) ^ include/linux/mmdebug.h:45:25: note: expanded from macro 'VM_BUG_ON' #define VM_BUG_ON(cond) BUILD_BUG_ON_INVALID(cond) ^ include/linux/build_bug.h:30:33: note: expanded from macro 'BUILD_BUG_ON_INVALID' #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e)))) ^ >> drivers/scsi/hisi_sas/hisi_sas_main.c:2579:41: warning: shift count >= width of type [-Wshift-count-overflow] error = dma_set_mask_and_coherent(dev, 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)) ^ ~~~ 1 warning and 1 error generated. -- In file included from drivers/scsi/scsi_sysfs.c:13: In file included from include/linux/blkdev.h:13: >> include/linux/pagemap.h:181:2: error: called object type 'void' is not a function or function pointer VM_BUG_ON_PAGE(page_count(page) == 0, page); ^ include/linux/mmdebug.h:46:36: note: expanded from macro 'VM_BUG_ON_PAGE' #define VM_BUG_ON_PAGE(cond, page) VM_BUG_ON(cond) ^ include/linux/mmdebug.h:45:25: note: expanded from macro 'VM_BUG_ON' #define VM_BUG_ON(cond) BUILD_BUG_ON_INVALID(cond) ^ include/linux/build_bug.h:30:33: note: expanded from macro 'BUILD_BUG_ON_INVALID' #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e)))) ^ In file included from drivers/scsi/scsi_sysfs.c:20: In file included from include/scsi/scsi_tcq.h:6: In file included from include/scsi/scsi_cmnd.h:5: 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)) ^~~~~ drivers/scsi/scsi_sysfs.c:373:1: warning: format specifies type 'short' but the argument has type 'int' [-Wformat] shost_rd_attr(can_queue, "%hd\n"); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ %d drivers/scsi/scsi_sysfs.c:176:45: note: expanded from macro 'shost_rd_attr' #define shost_rd_attr(field, format_string) \ ^ drivers/scsi/scsi_sysfs.c:173:2: note: expanded from macro '\ shost_rd_attr2' shost_show_function(name, field, format_string) \ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/scsi/scsi_sysfs.c:165:43: note: expanded from macro 'shost_show_function' return snprintf (buf, 20, format_string, shost->field); \ ~~~~~~~~~~~~~ ^~~~~~~~~~~~ drivers/scsi/scsi_sysfs.c:1027:10: fatal error: 'scsi_devinfo_tbl.c' file not found #include "scsi_devinfo_tbl.c" ^~~~~~~~~~~~~~~~~~~~ 2 warnings and 2 errors generated. # https://github.com/0day-ci/linux/commit/a4a0f54fdd08d95dfe20d684b405db8a47fb61d8 git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Thomas-Gleixner/preempt-Make-preempt-count-unconditional/20200915-044640 git checkout a4a0f54fdd08d95dfe20d684b405db8a47fb61d8 vim +/void +181 include/linux/pagemap.h ^1da177e4c3f41 Linus Torvalds 2005-04-16 123 e286781d5f2e9c Nick Piggin 2008-07-25 124 /* e286781d5f2e9c Nick Piggin 2008-07-25 125 * speculatively take a reference to a page. 0139aa7b7fa12c Joonsoo Kim 2016-05-19 126 * If the page is free (_refcount == 0), then _refcount is untouched, and 0 0139aa7b7fa12c Joonsoo Kim 2016-05-19 127 * is returned. Otherwise, _refcount is incremented by 1 and 1 is returned. e286781d5f2e9c Nick Piggin 2008-07-25 128 * e286781d5f2e9c Nick Piggin 2008-07-25 129 * This function must be called inside the same rcu_read_lock() section as has e286781d5f2e9c Nick Piggin 2008-07-25 130 * been used to lookup the page in the pagecache radix-tree (or page table): 0139aa7b7fa12c Joonsoo Kim 2016-05-19 131 * this allows allocators to use a synchronize_rcu() to stabilize _refcount. e286781d5f2e9c Nick Piggin 2008-07-25 132 * e286781d5f2e9c Nick Piggin 2008-07-25 133 * Unless an RCU grace period has passed, the count of all pages coming out e286781d5f2e9c Nick Piggin 2008-07-25 134 * of the allocator must be considered unstable. page_count may return higher e286781d5f2e9c Nick Piggin 2008-07-25 135 * than expected, and put_page must be able to do the right thing when the e286781d5f2e9c Nick Piggin 2008-07-25 136 * page has been finished with, no matter what it is subsequently allocated e286781d5f2e9c Nick Piggin 2008-07-25 137 * for (because put_page is what is used here to drop an invalid speculative e286781d5f2e9c Nick Piggin 2008-07-25 138 * reference). e286781d5f2e9c Nick Piggin 2008-07-25 139 * e286781d5f2e9c Nick Piggin 2008-07-25 140 * This is the interesting part of the lockless pagecache (and lockless e286781d5f2e9c Nick Piggin 2008-07-25 141 * get_user_pages) locking protocol, where the lookup-side (eg. find_get_page) e286781d5f2e9c Nick Piggin 2008-07-25 142 * has the following pattern: e286781d5f2e9c Nick Piggin 2008-07-25 143 * 1. find page in radix tree e286781d5f2e9c Nick Piggin 2008-07-25 144 * 2. conditionally increment refcount e286781d5f2e9c Nick Piggin 2008-07-25 145 * 3. check the page is still in pagecache (if no, goto 1) e286781d5f2e9c Nick Piggin 2008-07-25 146 * 0139aa7b7fa12c Joonsoo Kim 2016-05-19 147 * Remove-side that cares about stability of _refcount (eg. reclaim) has the b93b016313b3ba Matthew Wilcox 2018-04-10 148 * following (with the i_pages lock held): e286781d5f2e9c Nick Piggin 2008-07-25 149 * A. atomically check refcount is correct and set it to 0 (atomic_cmpxchg) e286781d5f2e9c Nick Piggin 2008-07-25 150 * B. remove page from pagecache e286781d5f2e9c Nick Piggin 2008-07-25 151 * C. free the page e286781d5f2e9c Nick Piggin 2008-07-25 152 * e286781d5f2e9c Nick Piggin 2008-07-25 153 * There are 2 critical interleavings that matter: e286781d5f2e9c Nick Piggin 2008-07-25 154 * - 2 runs before A: in this case, A sees elevated refcount and bails out e286781d5f2e9c Nick Piggin 2008-07-25 155 * - A runs before 2: in this case, 2 sees zero refcount and retries; e286781d5f2e9c Nick Piggin 2008-07-25 156 * subsequently, B will complete and 1 will find no page, causing the e286781d5f2e9c Nick Piggin 2008-07-25 157 * lookup to return NULL. e286781d5f2e9c Nick Piggin 2008-07-25 158 * e286781d5f2e9c Nick Piggin 2008-07-25 159 * It is possible that between 1 and 2, the page is removed then the exact same e286781d5f2e9c Nick Piggin 2008-07-25 160 * page is inserted into the same position in pagecache. That's OK: the b93b016313b3ba Matthew Wilcox 2018-04-10 161 * old find_get_page using a lock could equally have run before or after e286781d5f2e9c Nick Piggin 2008-07-25 162 * such a re-insertion, depending on order that locks are granted. e286781d5f2e9c Nick Piggin 2008-07-25 163 * e286781d5f2e9c Nick Piggin 2008-07-25 164 * Lookups racing against pagecache insertion isn't a big problem: either 1 e286781d5f2e9c Nick Piggin 2008-07-25 165 * will find the page or it will not. Likewise, the old find_get_page could run e286781d5f2e9c Nick Piggin 2008-07-25 166 * either before the insertion or afterwards, depending on timing. e286781d5f2e9c Nick Piggin 2008-07-25 167 */ 494eec70f05496 john.hubbard@xxxxxxxxx 2019-03-05 168 static inline int __page_cache_add_speculative(struct page *page, int count) e286781d5f2e9c Nick Piggin 2008-07-25 169 { 8375ad98cc1def Paul E. McKenney 2013-04-29 170 #ifdef CONFIG_TINY_RCU a4a0f54fdd08d9 Thomas Gleixner 2020-09-14 171 VM_BUG_ON(preemptible()) e286781d5f2e9c Nick Piggin 2008-07-25 172 /* e286781d5f2e9c Nick Piggin 2008-07-25 173 * Preempt must be disabled here - we rely on rcu_read_lock doing e286781d5f2e9c Nick Piggin 2008-07-25 174 * this for us. e286781d5f2e9c Nick Piggin 2008-07-25 175 * e286781d5f2e9c Nick Piggin 2008-07-25 176 * Pagecache won't be truncated from interrupt context, so if we have e286781d5f2e9c Nick Piggin 2008-07-25 177 * found a page in the radix tree here, we have pinned its refcount by e286781d5f2e9c Nick Piggin 2008-07-25 178 * disabling preempt, and hence no need for the "speculative get" that e286781d5f2e9c Nick Piggin 2008-07-25 179 * SMP requires. e286781d5f2e9c Nick Piggin 2008-07-25 180 */ 309381feaee564 Sasha Levin 2014-01-23 @181 VM_BUG_ON_PAGE(page_count(page) == 0, page); 494eec70f05496 john.hubbard@xxxxxxxxx 2019-03-05 182 page_ref_add(page, count); e286781d5f2e9c Nick Piggin 2008-07-25 183 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx
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