[kbuild-all] Re: [PATCH] dma-buf: fix and rework dma_buf_poll

Hi "Christian, I love your patch! Perhaps something to improve: [auto build test WARNING on next-20210616] [cannot apply to tegra-drm/drm/tegra/for-next linus/master v5.13-rc6 v5.13-rc5 v5.13-rc4 v5.13-rc6] [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/Christian-K-nig/dma-buf-fix-and-... base: c7d4c1fd91ab4a6d2620497921a9c6bf54650ab8 config: s390-randconfig-r022-20210617 (attached as .config) compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 64720f57bea6a6bf033feef4a5751ab9c0c3b401) 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 s390 cross compiling tool for clang build # apt-get install binutils-s390x-linux-gnu # https://github.com/0day-ci/linux/commit/dfa9f2ec4c082b73e644e2c565e58e229... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Christian-K-nig/dma-buf-fix-and-rework-dma_buf_poll/20210617-103036 git checkout dfa9f2ec4c082b73e644e2c565e58e2291f94463 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=s390 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): dma_fence_put(fence_excl); ^~~~~~~~~~ drivers/dma-buf/dma-buf.c:213:30: note: initialize the variable 'fence_excl' to silence this warning struct dma_fence *fence_excl; ^ = NULL 1 warning generated. vim +/fence_excl +284 drivers/dma-buf/dma-buf.c 206 207 static __poll_t dma_buf_poll(struct file *file, poll_table *poll) 208 { 209 struct dma_buf_poll_cb_t *dcb; 210 struct dma_buf *dmabuf; 211 struct dma_resv *resv; 212 struct dma_resv_list *fobj; 213 struct dma_fence *fence_excl; 214 unsigned shared_count, seq; 215 struct dma_fence *fence; 216 __poll_t events; 217 int r, i; 218 219 dmabuf = file->private_data; 220 if (!dmabuf || !dmabuf->resv) 221 return EPOLLERR; 222 223 resv = dmabuf->resv; 224 225 poll_wait(file, &dmabuf->poll, poll); 226 227 events = poll_requested_events(poll) & (EPOLLIN | EPOLLOUT); 228 if (!events) 229 return 0; 230 231 dcb = events & EPOLLOUT ? &dmabuf->cb_out : &dmabuf->cb_in; 232 233 /* Only queue a new one if we are not still waiting for the old one */ 234 spin_lock_irq(&dmabuf->poll.lock); 235 if (dcb->active) 236 events = 0; 237 else 238 dcb->active = events; 239 spin_unlock_irq(&dmabuf->poll.lock); 240 if (!events) 241 return 0; 242 243 retry: 244 seq = read_seqcount_begin(&resv->seq); 245 rcu_read_lock(); 246 247 fobj = rcu_dereference(resv->fence); 248 if (fobj && events & EPOLLOUT) 249 shared_count = fobj->shared_count; 250 else 251 shared_count = 0; 252 253 for (i = 0; i < shared_count; ++i) { 254 fence = rcu_dereference(fobj->shared[i]); 255 fence = dma_fence_get_rcu(fence); 256 if (!fence || read_seqcount_retry(&resv->seq, seq)) { 257 /* Concurrent modify detected, force re-check */ 258 dma_fence_put(fence); 259 rcu_read_unlock(); 260 goto retry; 261 } 262 263 r = dma_fence_add_callback(fence, &dcb->cb, dma_buf_poll_cb); 264 dma_fence_put(fence); 265 if (!r) { 266 /* Callback queued */ 267 events = 0; 268 goto out; 269 } 270 } 271 272 fence = dma_resv_excl_fence(resv); 273 if (fence) { 274 fence = dma_fence_get_rcu(fence); 275 if (!fence || read_seqcount_retry(&resv->seq, seq)) { 276 /* Concurrent modify detected, force re-check */ 277 dma_fence_put(fence); 278 rcu_read_unlock(); 279 goto retry; 280 281 } 282 283 r = dma_fence_add_callback(fence, &dcb->cb, dma_buf_poll_cb); 285 if (!r) { 286 /* Callback queued */ 287 events = 0; 288 goto out; 289 } 290 } 291 292 /* No callback queued, wake up any additional waiters. */ 293 dma_buf_poll_cb(NULL, &dcb->cb); 294 295 out: 296 rcu_read_unlock(); 297 return events; 298 } 299 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org