4168203271
The code is racy and the check with cpuidle_curr_driver should be done under the lock. I don't find a path in the different drivers where that could happen because the arch specific drivers are written in such way it is not possible to register a driver while it is unregistered, except maybe in a very improbable case when "intel_idle" and "processor_idle" are competing. One could unregister a driver, while the other one is registering. Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
118 lines
2.5 KiB
C
118 lines
2.5 KiB
C
/*
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* driver.c - driver support
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*
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* (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
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* Shaohua Li <shaohua.li@intel.com>
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* Adam Belay <abelay@novell.com>
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*
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* This code is licenced under the GPL.
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*/
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#include <linux/mutex.h>
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#include <linux/module.h>
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#include <linux/cpuidle.h>
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#include "cpuidle.h"
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static struct cpuidle_driver *cpuidle_curr_driver;
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DEFINE_SPINLOCK(cpuidle_driver_lock);
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static void set_power_states(struct cpuidle_driver *drv)
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{
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int i;
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/*
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* cpuidle driver should set the drv->power_specified bit
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* before registering if the driver provides
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* power_usage numbers.
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*
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* If power_specified is not set,
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* we fill in power_usage with decreasing values as the
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* cpuidle code has an implicit assumption that state Cn
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* uses less power than C(n-1).
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*
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* With CONFIG_ARCH_HAS_CPU_RELAX, C0 is already assigned
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* an power value of -1. So we use -2, -3, etc, for other
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* c-states.
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*/
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for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++)
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drv->states[i].power_usage = -1 - i;
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}
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/**
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* cpuidle_register_driver - registers a driver
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* @drv: the driver
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*/
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int cpuidle_register_driver(struct cpuidle_driver *drv)
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{
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if (!drv || !drv->state_count)
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return -EINVAL;
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if (cpuidle_disabled())
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return -ENODEV;
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spin_lock(&cpuidle_driver_lock);
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if (cpuidle_curr_driver) {
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spin_unlock(&cpuidle_driver_lock);
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return -EBUSY;
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}
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if (!drv->power_specified)
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set_power_states(drv);
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drv->refcnt = 0;
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cpuidle_curr_driver = drv;
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spin_unlock(&cpuidle_driver_lock);
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return 0;
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}
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EXPORT_SYMBOL_GPL(cpuidle_register_driver);
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/**
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* cpuidle_get_driver - return the current driver
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*/
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struct cpuidle_driver *cpuidle_get_driver(void)
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{
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return cpuidle_curr_driver;
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}
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EXPORT_SYMBOL_GPL(cpuidle_get_driver);
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/**
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* cpuidle_unregister_driver - unregisters a driver
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* @drv: the driver
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*/
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void cpuidle_unregister_driver(struct cpuidle_driver *drv)
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{
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spin_lock(&cpuidle_driver_lock);
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if (drv == cpuidle_curr_driver && !WARN_ON(drv->refcnt > 0))
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cpuidle_curr_driver = NULL;
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spin_unlock(&cpuidle_driver_lock);
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}
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EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
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struct cpuidle_driver *cpuidle_driver_ref(void)
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{
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struct cpuidle_driver *drv;
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spin_lock(&cpuidle_driver_lock);
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drv = cpuidle_curr_driver;
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drv->refcnt++;
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spin_unlock(&cpuidle_driver_lock);
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return drv;
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}
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void cpuidle_driver_unref(void)
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{
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struct cpuidle_driver *drv = cpuidle_curr_driver;
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spin_lock(&cpuidle_driver_lock);
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if (drv && !WARN_ON(drv->refcnt <= 0))
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drv->refcnt--;
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spin_unlock(&cpuidle_driver_lock);
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}
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