kernel.git/drivers/cpufreq/cpufreq.c, branch linux-5.19.y

cpufreq: check only freq_table in __resolve_freq()

2022-09-15T08:47:09Z

[ Upstream commit 6ca7076fbfaeccce173aeab832d76b9e49e1034b ] There is no need to check if the cpufreq driver implements callback cpufreq_driver::target_index. The logic in the __resolve_freq uses the frequency table available in the policy. It doesn't matter if the driver provides 'target_index' or 'target' callback. It just has to populate the 'policy->freq_table'. Thus, check only frequency table during the frequency resolving call. Acked-by: Viresh Kumar Signed-off-by: Lukasz Luba Signed-off-by: Rafael J. Wysocki Signed-off-by: Sasha Levin

cpufreq: make interface functions and lock holding state clear

2022-05-17T19:39:05Z

cpufreq_offline() calls offline() and exit() under the policy rwsem But they are called outside the rwsem in cpufreq_online(). Make cpufreq_online() call offline() and exit() as well as online() and init() under the policy rwsem to achieve a clear lock relationship. All of the init() and online() implementations in the tree only initialize the policy object without attempting to acquire the policy rwsem and they won't call cpufreq APIs attempting to acquire it. Signed-off-by: Schspa Shi Acked-by: Viresh Kumar [ rjw: Changelog edits ] Signed-off-by: Rafael J. Wysocki

cpufreq: Abort show()/store() for half-initialized policies

2022-05-17T19:39:04Z

If policy initialization fails after the sysfs files are created, there is a possibility to end up running show()/store() callbacks for half-initialized policies, which may have unpredictable outcomes. Abort show()/store() in such a case by making sure the policy is active. Also dectivate the policy on such failures. Signed-off-by: Schspa Shi Acked-by: Viresh Kumar [ rjw: Subject and changelog edits ] Signed-off-by: Rafael J. Wysocki

cpufreq: Rearrange locking in cpufreq_remove_dev()

2022-05-12T15:11:57Z

Currently, cpufreq_remove_dev() invokes the ->exit() driver callback without holding the policy rwsem which is inconsistent with what happens if ->exit() is invoked directly from cpufreq_offline(). It also manipulates the real_cpus mask and removes the CPU device symlink without holding the policy rwsem, but cpufreq_offline() holds the rwsem around the modifications thereof. For consistency, modify cpufreq_remove_dev() to hold the policy rwsem until the ->exit() callback has been called (or it has been determined that it is not necessary to call it). Signed-off-by: Rafael J. Wysocki Acked-by: Viresh Kumar

cpufreq: Split cpufreq_offline()

2022-05-12T15:11:57Z

Split the "core" part running under the policy rwsem out of cpufreq_offline() to allow the locking in cpufreq_remove_dev() to be rearranged more easily. As a side-effect this eliminates the unlock label that's not needed any more. No expected functional impact. Signed-off-by: Rafael J. Wysocki Acked-by: Viresh Kumar

cpufreq: Reorganize checks in cpufreq_offline()

2022-05-12T15:11:57Z

Notice that cpufreq_offline() only needs to check policy_is_inactive() once and rearrange the code in there to make that happen. No expected functional impact. Signed-off-by: Rafael J. Wysocki Acked-by: Viresh Kumar

cpufreq: Clear real_cpus mask from remove_cpu_dev_symlink()

2022-05-11T17:23:10Z

add_cpu_dev_symlink() is responsible for setting the CPUs in the real_cpus mask, the reverse of which should be done from remove_cpu_dev_symlink() to make it look clean and avoid any breakage later on. Move the call to clear the mask to remove_cpu_dev_symlink(). Signed-off-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki

Revert "cpufreq: Fix possible race in cpufreq online error path"

2022-05-09T16:51:54Z

This reverts commit f346e96267cd76175d6c201b40f770c0116a8a04. The commit tried to fix a possible real bug but it made it even worse. The fix was simply buggy as now an error out to out_offline_policy or out_exit_policy will try to release a semaphore which was never taken in the first place. This works fine only if we failed late, i.e. via out_destroy_policy. Fixes: f346e96267cd ("cpufreq: Fix possible race in cpufreq online error path") Signed-off-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki

cpufreq: Avoid unnecessary frequency updates due to mismatch

2022-05-06T18:56:21Z

For some platforms, the frequency returned by hardware may be slightly different from what is provided in the frequency table. For example, hardware may return 499 MHz instead of 500 MHz. In such cases it is better to avoid getting into unnecessary frequency updates, as we may end up switching policy->cur between the two and sending unnecessary pre/post update notifications, etc. This patch has chosen allows the hardware frequency and table frequency to deviate by 1 MHz for now, we may want to increase it a bit later on if someone still complains. Reported-by: Rex-BC Chen Signed-off-by: Viresh Kumar Tested-by: Jia-wei Chang Reviewed-by: Matthias Brugger Signed-off-by: Rafael J. Wysocki

cpufreq: Fix possible race in cpufreq online error path

2022-04-22T16:17:48Z

When cpufreq online fails, the policy->cpus mask is not cleared and policy->rwsem is released too early, so the driver can be invoked via the cpuinfo_cur_freq sysfs attribute while its ->offline() or ->exit() callbacks are being run. Take policy->clk as an example: static int cpufreq_online(unsigned int cpu) { ... // policy->cpus != 0 at this time down_write(&policy->rwsem); ret = cpufreq_add_dev_interface(policy); up_write(&policy->rwsem); return 0; out_destroy_policy: for_each_cpu(j, policy->real_cpus) remove_cpu_dev_symlink(policy, get_cpu_device(j)); up_write(&policy->rwsem); ... out_exit_policy: if (cpufreq_driver->exit) cpufreq_driver->exit(policy); clk_put(policy->clk); // policy->clk is a wild pointer ... ^ | Another process access __cpufreq_get cpufreq_verify_current_freq cpufreq_generic_get // acces wild pointer of policy->clk; | | out_offline_policy: | cpufreq_policy_free(policy); | // deleted here, and will wait for no body reference cpufreq_policy_put_kobj(policy); } Address this by modifying cpufreq_online() to release policy->rwsem in the error path after the driver callbacks have run and to clear policy->cpus before releasing the semaphore. Fixes: 7106e02baed4 ("cpufreq: release policy->rwsem on error") Signed-off-by: Schspa Shi [ rjw: Subject and changelog edits ] Signed-off-by: Rafael J. Wysocki