Re: [PATCH v8 4/8] PM / EM: add support for other devices than CPUs in Energy Model

[Dan Carpenter <dan.carpenter@oracle.com>]

[-- Attachment #1: Type: text/plain, Size: 5767 bytes --]

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@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>

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?

110d050cb7ba1c Lukasz Luba     2020-05-27  313  	if (ret)
27871f7a8a341e Quentin Perret  2018-12-03  314  		goto unlock;
27871f7a8a341e Quentin Perret  2018-12-03  315  
110d050cb7ba1c Lukasz Luba     2020-05-27 @316  	em_debug_create_pd(dev);
                                                                           ^^^
Dereferences dev->em_pd.

110d050cb7ba1c Lukasz Luba     2020-05-27  317  	dev_info(dev, "EM: created perf domain\n");
27871f7a8a341e Quentin Perret  2018-12-03  318  
27871f7a8a341e Quentin Perret  2018-12-03  319  unlock:
27871f7a8a341e Quentin Perret  2018-12-03  320  	mutex_unlock(&em_pd_mutex);
27871f7a8a341e Quentin Perret  2018-12-03  321  	return ret;
27871f7a8a341e Quentin Perret  2018-12-03  322  }
0e294e607adaf3 Lukasz Luba     2020-05-27  323  EXPORT_SYMBOL_GPL(em_dev_register_perf_domain);

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

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 28764 bytes --]