c6d22b3726
A deadlock may occur if one of the PM domains' .start_device() or .stop_device() callbacks or a device driver's .runtime_suspend() or .runtime_resume() callback executed by the core generic PM domain code uses a "wrong" runtime PM helper function. This happens, for example, if .runtime_resume() from one device's driver calls pm_runtime_resume() for another device in the same PM domain. A similar situation may take place if a device's parent is in the same PM domain, in which case the runtime PM framework may execute pm_genpd_runtime_resume() automatically for the parent (if it is suspended at the moment). This, of course, is undesirable, so the generic PM domains code should be modified to prevent it from happening. The runtime PM framework guarantees that pm_genpd_runtime_suspend() and pm_genpd_runtime_resume() won't be executed in parallel for the same device, so the generic PM domains code need not worry about those cases. Still, it needs to prevent the other possible race conditions between pm_genpd_runtime_suspend(), pm_genpd_runtime_resume(), pm_genpd_poweron() and pm_genpd_poweroff() from happening and it needs to avoid deadlocks at the same time. To this end, modify the generic PM domains code to relax synchronization rules so that: * pm_genpd_poweron() doesn't wait for the PM domain status to change from GPD_STATE_BUSY. If it finds that the status is not GPD_STATE_POWER_OFF, it returns without powering the domain on (it may modify the status depending on the circumstances). * pm_genpd_poweroff() returns as soon as it finds that the PM domain's status changed from GPD_STATE_BUSY after it's released the PM domain's lock. * pm_genpd_runtime_suspend() doesn't wait for the PM domain status to change from GPD_STATE_BUSY after executing the domain's .stop_device() callback and executes pm_genpd_poweroff() only if pm_genpd_runtime_resume() is not executed in parallel. * pm_genpd_runtime_resume() doesn't wait for the PM domain status to change from GPD_STATE_BUSY after executing pm_genpd_poweron() and sets the domain's status to GPD_STATE_BUSY and increments its counter of resuming devices (introduced by this change) immediately after acquiring the lock. The counter of resuming devices is then decremented after executing __pm_genpd_runtime_resume() for the device and the domain's status is reset to GPD_STATE_ACTIVE (unless there are more resuming devices in the domain, in which case the status remains GPD_STATE_BUSY). This way, for example, if a device driver's .runtime_resume() callback executes pm_runtime_resume() for another device in the same PM domain, pm_genpd_poweron() called by pm_genpd_runtime_resume() invoked by the runtime PM framework will not block and it will see that there's nothing to do for it. Next, the PM domain's lock will be acquired without waiting for its status to change from GPD_STATE_BUSY and the device driver's .runtime_resume() callback will be executed. In turn, if pm_runtime_suspend() is executed by one device driver's .runtime_resume() callback for another device in the same PM domain, pm_genpd_poweroff() executed by pm_genpd_runtime_suspend() invoked by the runtime PM framework as a result will notice that one of the devices in the domain is being resumed, so it will return immediately. Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
104 lines
3.4 KiB
C
104 lines
3.4 KiB
C
/*
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* pm_domain.h - Definitions and headers related to device power domains.
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*
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* Copyright (C) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
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*
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* This file is released under the GPLv2.
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*/
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#ifndef _LINUX_PM_DOMAIN_H
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#define _LINUX_PM_DOMAIN_H
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#include <linux/device.h>
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enum gpd_status {
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GPD_STATE_ACTIVE = 0, /* PM domain is active */
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GPD_STATE_BUSY, /* Something is happening to the PM domain */
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GPD_STATE_REPEAT, /* Power off in progress, to be repeated */
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GPD_STATE_POWER_OFF, /* PM domain is off */
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};
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struct dev_power_governor {
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bool (*power_down_ok)(struct dev_pm_domain *domain);
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};
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struct generic_pm_domain {
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struct dev_pm_domain domain; /* PM domain operations */
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struct list_head sd_node; /* Node in the parent's subdomain list */
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struct generic_pm_domain *parent; /* Parent PM domain */
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struct list_head sd_list; /* List of dubdomains */
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struct list_head dev_list; /* List of devices */
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struct mutex lock;
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struct dev_power_governor *gov;
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struct work_struct power_off_work;
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unsigned int in_progress; /* Number of devices being suspended now */
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unsigned int sd_count; /* Number of subdomains with power "on" */
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enum gpd_status status; /* Current state of the domain */
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wait_queue_head_t status_wait_queue;
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struct task_struct *poweroff_task; /* Powering off task */
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unsigned int resume_count; /* Number of devices being resumed */
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unsigned int device_count; /* Number of devices */
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unsigned int suspended_count; /* System suspend device counter */
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unsigned int prepared_count; /* Suspend counter of prepared devices */
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bool suspend_power_off; /* Power status before system suspend */
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int (*power_off)(struct generic_pm_domain *domain);
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int (*power_on)(struct generic_pm_domain *domain);
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int (*start_device)(struct device *dev);
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int (*stop_device)(struct device *dev);
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bool (*active_wakeup)(struct device *dev);
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};
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static inline struct generic_pm_domain *pd_to_genpd(struct dev_pm_domain *pd)
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{
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return container_of(pd, struct generic_pm_domain, domain);
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}
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struct dev_list_entry {
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struct list_head node;
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struct device *dev;
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bool need_restore;
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};
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#ifdef CONFIG_PM_GENERIC_DOMAINS
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extern int pm_genpd_add_device(struct generic_pm_domain *genpd,
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struct device *dev);
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extern int pm_genpd_remove_device(struct generic_pm_domain *genpd,
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struct device *dev);
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extern int pm_genpd_add_subdomain(struct generic_pm_domain *genpd,
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struct generic_pm_domain *new_subdomain);
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extern int pm_genpd_remove_subdomain(struct generic_pm_domain *genpd,
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struct generic_pm_domain *target);
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extern void pm_genpd_init(struct generic_pm_domain *genpd,
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struct dev_power_governor *gov, bool is_off);
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extern int pm_genpd_poweron(struct generic_pm_domain *genpd);
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#else
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static inline int pm_genpd_add_device(struct generic_pm_domain *genpd,
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struct device *dev)
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{
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return -ENOSYS;
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}
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static inline int pm_genpd_remove_device(struct generic_pm_domain *genpd,
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struct device *dev)
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{
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return -ENOSYS;
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}
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static inline int pm_genpd_add_subdomain(struct generic_pm_domain *genpd,
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struct generic_pm_domain *new_sd)
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{
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return -ENOSYS;
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}
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static inline int pm_genpd_remove_subdomain(struct generic_pm_domain *genpd,
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struct generic_pm_domain *target)
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{
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return -ENOSYS;
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}
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static inline void pm_genpd_init(struct generic_pm_domain *genpd,
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struct dev_power_governor *gov, bool is_off) {}
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static inline int pm_genpd_poweron(struct generic_pm_domain *genpd)
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{
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return -ENOSYS;
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}
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#endif
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#endif /* _LINUX_PM_DOMAIN_H */
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