[norov:bitmap-fast6 5/9] drivers/infiniband/sw/siw/siw_main.c:196:6: warning: variable 'num_cpus' is used uninitialized whenever 'if' condition is false

From: kernel test robot
Date: Sun Nov 28 2021 - 09:53:35 EST


tree: https://github.com/norov/linux bitmap-fast6
head: a24f3834dc8fc58441c4219de9be07bce33b56fb
commit: de4cae808c1983b730d4e53057fa40af17133ffe [5/9] lib/cpumask: add cpumask_weight_{eq,gt,le}
config: arm-randconfig-r016-20211128 (https://download.01.org/0day-ci/archive/20211128/202111282209.RD5WM62X-lkp@xxxxxxxxx/config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 5c64d8ef8cc0c0ed3e0f2ae693d99e7f70f20a84)
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
# https://github.com/norov/linux/commit/de4cae808c1983b730d4e53057fa40af17133ffe
git remote add norov https://github.com/norov/linux
git fetch --no-tags norov bitmap-fast6
git checkout de4cae808c1983b730d4e53057fa40af17133ffe
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash drivers/infiniband/sw/siw/

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

All warnings (new ones prefixed by >>):

>> drivers/infiniband/sw/siw/siw_main.c:196:6: warning: variable 'num_cpus' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
if (cpumask_empty(tx_cpumask)) {
^~~~~~~~~~~~~~~~~~~~~~~~~
drivers/infiniband/sw/siw/siw_main.c:201:7: note: uninitialized use occurs here
if (!num_cpus)
^~~~~~~~
drivers/infiniband/sw/siw/siw_main.c:196:2: note: remove the 'if' if its condition is always true
if (cpumask_empty(tx_cpumask)) {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/infiniband/sw/siw/siw_main.c:189:17: note: initialize the variable 'num_cpus' to silence this warning
int i, num_cpus, cpu, min_use, node = sdev->numa_node, tx_cpu = -1;
^
= 0
1 warning generated.


vim +196 drivers/infiniband/sw/siw/siw_main.c

181
182 /*
183 * Choose CPU with least number of active QP's from NUMA node of
184 * TX interface.
185 */
186 int siw_get_tx_cpu(struct siw_device *sdev)
187 {
188 const struct cpumask *tx_cpumask;
189 int i, num_cpus, cpu, min_use, node = sdev->numa_node, tx_cpu = -1;
190
191 if (node < 0)
192 tx_cpumask = cpu_online_mask;
193 else
194 tx_cpumask = siw_cpu_info.tx_valid_cpus[node];
195
> 196 if (cpumask_empty(tx_cpumask)) {
197 /* no CPU on this NUMA node */
198 tx_cpumask = cpu_online_mask;
199 num_cpus = cpumask_weight(tx_cpumask);
200 }
201 if (!num_cpus)
202 goto out;
203
204 cpu = cpumask_first(tx_cpumask);
205
206 for (i = 0, min_use = SIW_MAX_QP; i < num_cpus;
207 i++, cpu = cpumask_next(cpu, tx_cpumask)) {
208 int usage;
209
210 /* Skip any cores which have no TX thread */
211 if (!siw_tx_thread[cpu])
212 continue;
213
214 usage = atomic_read(&per_cpu(siw_use_cnt, cpu));
215 if (usage <= min_use) {
216 tx_cpu = cpu;
217 min_use = usage;
218 }
219 }
220 siw_dbg(&sdev->base_dev,
221 "tx cpu %d, node %d, %d qp's\n", tx_cpu, node, min_use);
222
223 out:
224 if (tx_cpu >= 0)
225 atomic_inc(&per_cpu(siw_use_cnt, tx_cpu));
226 else
227 pr_warn("siw: no tx cpu found\n");
228
229 return tx_cpu;
230 }
231

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