On Mon, Jun 08, 2020 at 01:34:37PM +0100, Lukasz Luba wrote: > Hi Dan, > > Thank you for your analyzes. > > On 6/8/20 12:51 PM, Dan Carpenter wrote: > > Hi Lukasz, > > > > I love your patch! Perhaps something to improve: > > > > url: https://github.com/0day-ci/linux/commits/Lukasz-Luba/Add-support-for-devices-in-the-Energy-Model/20200527-180614 > > base: https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git linux-next > > > > config: i386-randconfig-m021-20200605 (attached as .config) > > compiler: gcc-9 (Debian 9.3.0-13) 9.3.0 > > > > If you fix the issue, kindly add following tag as appropriate > > Reported-by: kernel test robot <lkp@xxxxxxxxx> > > Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> > > > > smatch warnings: > > kernel/power/energy_model.c:316 em_dev_register_perf_domain() error: we previously assumed 'dev->em_pd' could be null (see line 277) > > > > # https://github.com/0day-ci/linux/commit/110d050cb7ba1c96e63ada498979d1fd99529be2 > > git remote add linux-review https://github.com/0day-ci/linux > > git remote update linux-review > > git checkout 110d050cb7ba1c96e63ada498979d1fd99529be2 > > vim +316 kernel/power/energy_model.c > > > > 0e294e607adaf3 Lukasz Luba 2020-05-27 262 int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states, > > 110d050cb7ba1c Lukasz Luba 2020-05-27 263 struct em_data_callback *cb, cpumask_t *cpus) > > 27871f7a8a341e Quentin Perret 2018-12-03 264 { > > 27871f7a8a341e Quentin Perret 2018-12-03 265 unsigned long cap, prev_cap = 0; > > 110d050cb7ba1c Lukasz Luba 2020-05-27 266 int cpu, ret; > > 27871f7a8a341e Quentin Perret 2018-12-03 267 > > 110d050cb7ba1c Lukasz Luba 2020-05-27 268 if (!dev || !nr_states || !cb) > > 27871f7a8a341e Quentin Perret 2018-12-03 269 return -EINVAL; > > 27871f7a8a341e Quentin Perret 2018-12-03 270 > > 27871f7a8a341e Quentin Perret 2018-12-03 271 /* > > 27871f7a8a341e Quentin Perret 2018-12-03 272 * Use a mutex to serialize the registration of performance domains and > > 27871f7a8a341e Quentin Perret 2018-12-03 273 * let the driver-defined callback functions sleep. > > 27871f7a8a341e Quentin Perret 2018-12-03 274 */ > > 27871f7a8a341e Quentin Perret 2018-12-03 275 mutex_lock(&em_pd_mutex); > > 27871f7a8a341e Quentin Perret 2018-12-03 276 > > 110d050cb7ba1c Lukasz Luba 2020-05-27 @277 if (dev->em_pd) { > > ^^^^^^^^^^ > > Check for NULL. > > > > 27871f7a8a341e Quentin Perret 2018-12-03 278 ret = -EEXIST; > > 27871f7a8a341e Quentin Perret 2018-12-03 279 goto unlock; > > 27871f7a8a341e Quentin Perret 2018-12-03 280 } > > 27871f7a8a341e Quentin Perret 2018-12-03 281 > > 110d050cb7ba1c Lukasz Luba 2020-05-27 282 if (_is_cpu_device(dev)) { > > 110d050cb7ba1c Lukasz Luba 2020-05-27 283 if (!cpus) { > > 110d050cb7ba1c Lukasz Luba 2020-05-27 284 dev_err(dev, "EM: invalid CPU mask\n"); > > 110d050cb7ba1c Lukasz Luba 2020-05-27 285 ret = -EINVAL; > > 110d050cb7ba1c Lukasz Luba 2020-05-27 286 goto unlock; > > 110d050cb7ba1c Lukasz Luba 2020-05-27 287 } > > 110d050cb7ba1c Lukasz Luba 2020-05-27 288 > > 110d050cb7ba1c Lukasz Luba 2020-05-27 289 for_each_cpu(cpu, cpus) { > > 110d050cb7ba1c Lukasz Luba 2020-05-27 290 if (em_cpu_get(cpu)) { > > 110d050cb7ba1c Lukasz Luba 2020-05-27 291 dev_err(dev, "EM: exists for CPU%d\n", cpu); > > 110d050cb7ba1c Lukasz Luba 2020-05-27 292 ret = -EEXIST; > > 110d050cb7ba1c Lukasz Luba 2020-05-27 293 goto unlock; > > 110d050cb7ba1c Lukasz Luba 2020-05-27 294 } > > 27871f7a8a341e Quentin Perret 2018-12-03 295 /* > > 110d050cb7ba1c Lukasz Luba 2020-05-27 296 * All CPUs of a domain must have the same > > 110d050cb7ba1c Lukasz Luba 2020-05-27 297 * micro-architecture since they all share the same > > 110d050cb7ba1c Lukasz Luba 2020-05-27 298 * table. > > 27871f7a8a341e Quentin Perret 2018-12-03 299 */ > > 8ec59c0f5f4966 Vincent Guittot 2019-06-17 300 cap = arch_scale_cpu_capacity(cpu); > > 27871f7a8a341e Quentin Perret 2018-12-03 301 if (prev_cap && prev_cap != cap) { > > 110d050cb7ba1c Lukasz Luba 2020-05-27 302 dev_err(dev, "EM: CPUs of %*pbl must have the same capacity\n", > > 110d050cb7ba1c Lukasz Luba 2020-05-27 303 cpumask_pr_args(cpus)); > > 110d050cb7ba1c Lukasz Luba 2020-05-27 304 > > 27871f7a8a341e Quentin Perret 2018-12-03 305 ret = -EINVAL; > > 27871f7a8a341e Quentin Perret 2018-12-03 306 goto unlock; > > 27871f7a8a341e Quentin Perret 2018-12-03 307 } > > 27871f7a8a341e Quentin Perret 2018-12-03 308 prev_cap = cap; > > 27871f7a8a341e Quentin Perret 2018-12-03 309 } > > 110d050cb7ba1c Lukasz Luba 2020-05-27 310 } > > 27871f7a8a341e Quentin Perret 2018-12-03 311 > > 110d050cb7ba1c Lukasz Luba 2020-05-27 312 ret = em_create_pd(dev, nr_states, cb, cpus); > > > > > > If it's a _is_cpu_device() then it iterates through a bunch of devices > > and sets up cpu_dev->em_pd for each. Presumably one of the devices is > > "dev" or this would crash pretty early on in testing? > > Yes, all of the devices taken from 'cpus' mask will get the em_pd set > including the suspected @dev. > To calm down this static analyzer I can remove the 'else' > in line 204 to make 'dev->em_pd = pd' set always. > 199 if (_is_cpu_device(dev)) > 200 for_each_cpu(cpu, cpus) { > 201 cpu_dev = get_cpu_device(cpu); > 202 cpu_dev->em_pd = pd; > 203 } > 204 else > 205 dev->em_pd = pd; > > > Do you think it's a good solution and will work for this tool? It's not about the tool... Ignore the tool when it's wrong. But I do think the code is slightly more clear without the else statement. Arguments could be made either way. Removing the else statement means we set dev->em_pd twice... But I *personally* lean vaguely towards removing the else statement. :P That would make the warning go away as well. regards, dan carpenter
