On 6/8/20 1:51 PM, Dan Carpenter wrote: > 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 >>> Reported-by: Dan Carpenter >>> >>> 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 Thanks, I will remove the else statement and add your 'Reported-by' Regards, Lukasz > > That would make the warning go away as well. > > regards, > dan carpenter >