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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2017-02-24 07:25:14 -0500
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2017-02-27 09:07:38 -0500
commit6dbf5cea05a7098a69f294c96b6d76f08562cae5 (patch)
treeb82971769598b518c88773bbb88874875a91aa62
parent37efa4b41ffb31dcdfc3beb97d47992bb2a083e5 (diff)
cpuidle: menu: Avoid taking spinlock for accessing QoS values
After commit 9908859acaa9 (cpuidle/menu: add per CPU PM QoS resume latency consideration) the cpuidle menu governor calls dev_pm_qos_read_value() on CPU devices to read the current resume latency QoS constraint values for them. That function takes a spinlock to prevent the device's power.qos pointer from becoming NULL during the access which is a problem for the RT patchset where spinlocks are converted into mutexes and the idle loop stops working. However, it is not even necessary for the menu governor to take that spinlock, because the power.qos pointer accessed under it cannot be modified during the access anyway. For this reason, introduce a "raw" routine for accessing device QoS resume latency constraints without locking and use it in the menu governor. Fixes: 9908859acaa9 (cpuidle/menu: add per CPU PM QoS resume latency consideration) Acked-by: Alex Shi <alex.shi@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
-rw-r--r--drivers/base/power/qos.c3
-rw-r--r--drivers/cpuidle/governors/menu.c2
-rw-r--r--include/linux/pm_qos.h7
3 files changed, 9 insertions, 3 deletions
diff --git a/drivers/base/power/qos.c b/drivers/base/power/qos.c
index 58fcc758334e..73142d086240 100644
--- a/drivers/base/power/qos.c
+++ b/drivers/base/power/qos.c
@@ -108,8 +108,7 @@ s32 __dev_pm_qos_read_value(struct device *dev)
108{ 108{
109 lockdep_assert_held(&dev->power.lock); 109 lockdep_assert_held(&dev->power.lock);
110 110
111 return IS_ERR_OR_NULL(dev->power.qos) ? 111 return dev_pm_qos_raw_read_value(dev);
112 0 : pm_qos_read_value(&dev->power.qos->resume_latency);
113} 112}
114 113
115/** 114/**
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 8d6d25c38c02..6d6f46e79d94 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -287,7 +287,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
287 unsigned int interactivity_req; 287 unsigned int interactivity_req;
288 unsigned int expected_interval; 288 unsigned int expected_interval;
289 unsigned long nr_iowaiters, cpu_load; 289 unsigned long nr_iowaiters, cpu_load;
290 int resume_latency = dev_pm_qos_read_value(device); 290 int resume_latency = dev_pm_qos_raw_read_value(device);
291 291
292 if (data->needs_update) { 292 if (data->needs_update) {
293 menu_update(drv, dev); 293 menu_update(drv, dev);
diff --git a/include/linux/pm_qos.h b/include/linux/pm_qos.h
index 0f65d36c2a75..5aba9f47899d 100644
--- a/include/linux/pm_qos.h
+++ b/include/linux/pm_qos.h
@@ -173,6 +173,12 @@ static inline s32 dev_pm_qos_requested_flags(struct device *dev)
173{ 173{
174 return dev->power.qos->flags_req->data.flr.flags; 174 return dev->power.qos->flags_req->data.flr.flags;
175} 175}
176
177static inline s32 dev_pm_qos_raw_read_value(struct device *dev)
178{
179 return IS_ERR_OR_NULL(dev->power.qos) ?
180 0 : pm_qos_read_value(&dev->power.qos->resume_latency);
181}
176#else 182#else
177static inline enum pm_qos_flags_status __dev_pm_qos_flags(struct device *dev, 183static inline enum pm_qos_flags_status __dev_pm_qos_flags(struct device *dev,
178 s32 mask) 184 s32 mask)
@@ -237,6 +243,7 @@ static inline void dev_pm_qos_hide_latency_tolerance(struct device *dev) {}
237 243
238static inline s32 dev_pm_qos_requested_resume_latency(struct device *dev) { return 0; } 244static inline s32 dev_pm_qos_requested_resume_latency(struct device *dev) { return 0; }
239static inline s32 dev_pm_qos_requested_flags(struct device *dev) { return 0; } 245static inline s32 dev_pm_qos_requested_flags(struct device *dev) { return 0; }
246static inline s32 dev_pm_qos_raw_read_value(struct device *dev) { return 0; }
240#endif 247#endif
241 248
242#endif 249#endif