kernel.git/drivers/cpufreq/cpufreq.c, branch linux-4.4.y

Revert "cpufreq: Drop rwsem lock around CPUFREQ_GOV_POLICY_EXIT"

2020-05-10T08:26:24Z

commit 68e80dae09033d778b98dc88e5bfe8fdade188e5 upstream. Earlier, when the struct freq-attr was used to represent governor attributes, the standard cpufreq show/store sysfs attribute callbacks were applied to the governor tunable attributes and they always acquire the policy->rwsem lock before carrying out the operation. That could have resulted in an ABBA deadlock if governor tunable attributes are removed under policy->rwsem while one of them is being accessed concurrently (if sysfs attributes removal wins the race, it will wait for the access to complete with policy->rwsem held while the attribute callback will block on policy->rwsem indefinitely). We attempted to address this issue by dropping policy->rwsem around governor tunable attributes removal (that is, around invocations of the ->governor callback with the event arg equal to CPUFREQ_GOV_POLICY_EXIT) in cpufreq_set_policy(), but that opened up race conditions that had not been possible with policy->rwsem held all the time. The previous commit, "cpufreq: governor: New sysfs show/store callbacks for governor tunables", fixed the original ABBA deadlock by adding new governor specific show/store callbacks. We don't have to drop rwsem around invocations of governor event CPUFREQ_GOV_POLICY_EXIT anymore, and original fix can be reverted now. Fixes: 955ef4833574 (cpufreq: Drop rwsem lock around CPUFREQ_GOV_POLICY_EXIT) Signed-off-by: Viresh Kumar Reported-by: Juri Lelli Tested-by: Juri Lelli Tested-by: Shilpasri G Bhat Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman

cpufreq: Register drivers only after CPU devices have been registered

2020-01-04T12:34:16Z

[ Upstream commit 46770be0cf94149ca48be87719bda1d951066644 ] The cpufreq core heavily depends on the availability of the struct device for CPUs and if they aren't available at the time cpufreq driver is registered, we will never succeed in making cpufreq work. This happens due to following sequence of events: - cpufreq_register_driver() - subsys_interface_register() - return 0; //successful registration of driver ... at a later point of time - register_cpu(); - device_register(); - bus_probe_device(); - sif->add_dev(); - cpufreq_add_dev(); - get_cpu_device(); //FAILS - per_cpu(cpu_sys_devices, num) = &cpu->dev; //used by get_cpu_device() - return 0; //CPU registered successfully Because the per-cpu variable cpu_sys_devices is set only after the CPU device is regsitered, cpufreq will never be able to get it when cpufreq_add_dev() is called. This patch avoids this failure by making sure device structure of at least CPU0 is available when the cpufreq driver is registered, else return -EPROBE_DEFER. Reported-by: Bjorn Andersson Co-developed-by: Amit Kucheria Signed-off-by: Viresh Kumar Tested-by: Amit Kucheria Signed-off-by: Rafael J. Wysocki Signed-off-by: Sasha Levin

cpufreq: Add NULL checks to show() and store() methods of cpufreq

2019-11-28T17:26:19Z

commit e6e8df07268c1f75dd9215536e2ce4587b70f977 upstream. Add NULL checks to show() and store() in cpufreq.c to avoid attempts to invoke a NULL callback. Though some interfaces of cpufreq are set as read-only, users can still get write permission using chmod which can lead to a kernel crash, as follows: chmod +w /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq echo 1 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq This bug was found in linux 4.19. Signed-off-by: Kai Shen Reported-by: Feilong Lin Reviewed-by: Feilong Lin Acked-by: Viresh Kumar [ rjw: Subject & changelog ] Cc: All applicable Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman

cpufreq: Skip cpufreq resume if it's not suspended

2019-11-28T17:26:14Z

commit 703cbaa601ff3fb554d1246c336ba727cc083ea0 upstream. cpufreq_resume can be called even without preceding cpufreq_suspend. This can happen in following scenario: suspend_devices_and_enter --> dpm_suspend_start --> dpm_prepare --> device_prepare : this function errors out --> dpm_suspend: this is skipped due to dpm_prepare failure this means cpufreq_suspend is skipped over --> goto Recover_platform, due to previous error --> goto Resume_devices --> dpm_resume_end --> dpm_resume --> cpufreq_resume In case schedutil is used as frequency governor, cpufreq_resume will eventually call sugov_start, which does following: memset(sg_cpu, 0, sizeof(*sg_cpu)); .... This effectively erases function pointer for frequency update, causing crash later on. The function pointer would have been set correctly if subsequent cpufreq_add_update_util_hook runs successfully, but that function returns earlier because cpufreq_suspend was not called: if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu))) return; The fix is to check cpufreq_suspended first, if it's false, that means cpufreq_suspend was not called in the first place, so do not resume cpufreq. Signed-off-by: Bo Yan Acked-by: Viresh Kumar [ rjw: Dropped printing a message ] Signed-off-by: Rafael J. Wysocki Signed-off-by: Lee Jones Signed-off-by: Greg Kroah-Hartman

cpufreq: Avoid cpufreq_suspend() deadlock on system shutdown

2019-10-29T08:13:31Z

commit 65650b35133ff20f0c9ef0abd5c3c66dbce3ae57 upstream. It is incorrect to set the cpufreq syscore shutdown callback pointer to cpufreq_suspend(), because that function cannot be run in the syscore stage of system shutdown for two reasons: (a) it may attempt to carry out actions depending on devices that have already been shut down at that point and (b) the RCU synchronization carried out by it may not be able to make progress then. The latter issue has been present since commit 45975c7d21a1 ("rcu: Define RCU-sched API in terms of RCU for Tree RCU PREEMPT builds"), but the former one has been there since commit 90de2a4aa9f3 ("cpufreq: suspend cpufreq governors on shutdown") regardless. Fix that by dropping cpufreq_syscore_ops altogether and making device_shutdown() call cpufreq_suspend() directly before shutting down devices, which is along the lines of what system-wide power management does. Fixes: 45975c7d21a1 ("rcu: Define RCU-sched API in terms of RCU for Tree RCU PREEMPT builds") Fixes: 90de2a4aa9f3 ("cpufreq: suspend cpufreq governors on shutdown") Reported-by: Ville Syrjälä Tested-by: Ville Syrjälä Signed-off-by: Rafael J. Wysocki Acked-by: Viresh Kumar Cc: 4.0+ # 4.0+ Signed-off-by: Greg Kroah-Hartman

cpufreq: Use struct kobj_attribute instead of struct global_attr

2019-03-23T07:44:21Z

commit 625c85a62cb7d3c79f6e16de3cfa972033658250 upstream. The cpufreq_global_kobject is created using kobject_create_and_add() helper, which assigns the kobj_type as dynamic_kobj_ktype and show/store routines are set to kobj_attr_show() and kobj_attr_store(). These routines pass struct kobj_attribute as an argument to the show/store callbacks. But all the cpufreq files created using the cpufreq_global_kobject expect the argument to be of type struct attribute. Things work fine currently as no one accesses the "attr" argument. We may not see issues even if the argument is used, as struct kobj_attribute has struct attribute as its first element and so they will both get same address. But this is logically incorrect and we should rather use struct kobj_attribute instead of struct global_attr in the cpufreq core and drivers and the show/store callbacks should take struct kobj_attribute as argument instead. This bug is caught using CFI CLANG builds in android kernel which catches mismatch in function prototypes for such callbacks. Reported-by: Donghee Han Reported-by: Sangkyu Kim Signed-off-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman

cpufreq: Fix new policy initialization during limits updates via sysfs

2018-07-03T09:21:26Z

commit c7d1f119c48f64bebf0fa1e326af577c6152fe30 upstream. If the policy limits are updated via cpufreq_update_policy() and subsequently via sysfs, the limits stored in user_policy may be set incorrectly. For example, if both min and max are set via sysfs to the maximum available frequency, user_policy.min and user_policy.max will also be the maximum. If a policy notifier triggered by cpufreq_update_policy() lowers both the min and the max at this point, that change is not reflected by the user_policy limits, so if the max is updated again via sysfs to the same lower value, then user_policy.max will be lower than user_policy.min which shouldn't happen. In particular, if one of the policy CPUs is then taken offline and back online, cpufreq_set_policy() will fail for it due to a failing limits check. To prevent that from happening, initialize the min and max fields of the new_policy object to the ones stored in user_policy that were previously set via sysfs. Signed-off-by: Kevin Wangtao Acked-by: Viresh Kumar [ rjw: Subject & changelog ] Cc: All applicable Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman

Revert "cpufreq: Fix governor module removal race"

2018-04-08T09:52:02Z

This reverts commit 3f7dfb7fcf98a7e73dee018c4a68537ce7fec646 which was commit a8b149d32b663c1a4105273295184b78f53d33cf upstream. The backport was not correct, so just drop it entirely. Reported-by: Ben Hutchings Cc: Rafael J. Wysocki Cc: Viresh Kumar Cc: Sasha Levin Signed-off-by: Greg Kroah-Hartman

cpufreq: Fix governor module removal race

2018-03-22T08:23:28Z

[ Upstream commit a8b149d32b663c1a4105273295184b78f53d33cf ] It is possible to remove a cpufreq governor module after cpufreq_parse_governor() has returned success in store_scaling_governor() and before cpufreq_set_policy() acquires a reference to it, because the governor list is not protected during that period and nothing prevents the governor from being unregistered then. Prevent that from happening by acquiring an extra reference to the governor module temporarily in cpufreq_parse_governor(), under cpufreq_governor_mutex, and dropping it in store_scaling_governor(), when cpufreq_set_policy() returns. Note that the second cpufreq_parse_governor() call site is fine, because it only cares about the policy member of new_policy. Signed-off-by: Rafael J. Wysocki Acked-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

cpufreq: cpufreq_register_driver() should return -ENODEV if init fails

2017-06-14T11:16:23Z

commit 6c77003677d5f1ce15f26d24360cb66c0bc07bb3 upstream. For a driver that does not set the CPUFREQ_STICKY flag, if all of the ->init() calls fail, cpufreq_register_driver() should return an error. This will prevent the driver from loading. Fixes: ce1bcfe94db8 (cpufreq: check cpufreq_policy_list instead of scanning policies for all CPUs) Signed-off-by: David Arcari Acked-by: Viresh Kumar Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman