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Power management fix for v4.14-rc7

Browse source 
This fixes a device power management quality of service (PM QoS)
 framework implementation issue causing "no restriction" requests
 for device resume latency, including "no restriction" set by user
 space, to effectively override requests with specific device
 resume latency requirements.
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Merge tag 'pm-4.14-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull power management fix from Rafael Wysocki:
 "This fixes a device power management quality of service (PM QoS)
  framework implementation issue causing 'no restriction' requests for
  device resume latency, including 'no restriction' set by user space,
  to effectively override requests with specific device resume latency
  requirements.

  It is late in the cycle, but the bug in question is in the 'user space
  can trigger unexpected behavior' category and the fix is
  stable-candidate, so here it goes"

* tag 'pm-4.14-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  PM / QoS: Fix device resume latency PM QoS
This commit is contained in:
Linus Torvalds 2017-10-26 19:10:39 +02:00
commit 5678255027
8 changed files with 63 additions and 35 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
Documentation/ABI/testing/sysfs-devices-power
View file

@ -211,7 +211,9 @@ Description:
device, after it has been suspended at run time, from a resume
request to the moment the device will be ready to process I/O,
in microseconds. If it is equal to 0, however, this means that
the PM QoS resume latency may be arbitrary.
the PM QoS resume latency may be arbitrary and the special value
"n/a" means that user space cannot accept any resume latency at
all for the given device.
Not all drivers support this attribute. If it isn't supported,
it is not present.

3
drivers/base/cpu.c
View file

@ -377,7 +377,8 @@ int register_cpu(struct cpu *cpu, int num)
per_cpu(cpu_sys_devices, num) = &cpu->dev;
register_cpu_under_node(num, cpu_to_node(num));
dev_pm_qos_expose_latency_limit(&cpu->dev, 0);
dev_pm_qos_expose_latency_limit(&cpu->dev,
PM_QOS_RESUME_LATENCY_NO_CONSTRAINT);
return 0;
}

53
drivers/base/power/domain_governor.c
View file

@ -14,23 +14,20 @@
static int dev_update_qos_constraint(struct device *dev, void *data)
{
s64 *constraint_ns_p = data;
s32 constraint_ns = -1;
s64 constraint_ns = -1;
if (dev->power.subsys_data && dev->power.subsys_data->domain_data)
constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns;
if (constraint_ns < 0) {
if (constraint_ns < 0)
constraint_ns = dev_pm_qos_read_value(dev);
constraint_ns *= NSEC_PER_USEC;
}
if (constraint_ns == 0)
if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
return 0;
/*
* constraint_ns cannot be negative here, because the device has been
* suspended.
*/
if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0)
constraint_ns *= NSEC_PER_USEC;
if (constraint_ns < *constraint_ns_p || *constraint_ns_p < 0)
*constraint_ns_p = constraint_ns;
return 0;
@ -63,10 +60,14 @@ static bool default_suspend_ok(struct device *dev)
spin_unlock_irqrestore(&dev->power.lock, flags);
if (constraint_ns < 0)
if (constraint_ns == 0)
return false;
constraint_ns *= NSEC_PER_USEC;
if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
constraint_ns = -1;
else
constraint_ns *= NSEC_PER_USEC;
/*
* We can walk the children without any additional locking, because
* they all have been suspended at this point and their
@ -76,14 +77,19 @@ static bool default_suspend_ok(struct device *dev)
device_for_each_child(dev, &constraint_ns,
dev_update_qos_constraint);
if (constraint_ns > 0) {
constraint_ns -= td->suspend_latency_ns +
td->resume_latency_ns;
if (constraint_ns == 0)
return false;
if (constraint_ns < 0) {
/* The children have no constraints. */
td->effective_constraint_ns = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
td->cached_suspend_ok = true;
} else {
constraint_ns -= td->suspend_latency_ns + td->resume_latency_ns;
if (constraint_ns > 0) {
td->effective_constraint_ns = constraint_ns;
td->cached_suspend_ok = true;
} else {
td->effective_constraint_ns = 0;
}
}
td->effective_constraint_ns = constraint_ns;
td->cached_suspend_ok = constraint_ns >= 0;
/*
* The children have been suspended already, so we don't need to take
@ -145,13 +151,14 @@ static bool __default_power_down_ok(struct dev_pm_domain *pd,
td = &to_gpd_data(pdd)->td;
constraint_ns = td->effective_constraint_ns;
/* default_suspend_ok() need not be called before us. */
if (constraint_ns < 0) {
if (constraint_ns < 0)
constraint_ns = dev_pm_qos_read_value(pdd->dev);
constraint_ns *= NSEC_PER_USEC;
}
if (constraint_ns == 0)
if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
continue;
constraint_ns *= NSEC_PER_USEC;
/*
* constraint_ns cannot be negative here, because the device has
* been suspended.

2
drivers/base/power/qos.c
View file

@ -189,7 +189,7 @@ static int dev_pm_qos_constraints_allocate(struct device *dev)
plist_head_init(&c->list);
c->target_value = PM_QOS_RESUME_LATENCY_DEFAULT_VALUE;
c->default_value = PM_QOS_RESUME_LATENCY_DEFAULT_VALUE;
c->no_constraint_value = PM_QOS_RESUME_LATENCY_DEFAULT_VALUE;
c->no_constraint_value = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
c->type = PM_QOS_MIN;
c->notifiers = n;

2
drivers/base/power/runtime.c
View file

@ -253,7 +253,7 @@ static int rpm_check_suspend_allowed(struct device *dev)
|| (dev->power.request_pending
&& dev->power.request == RPM_REQ_RESUME))
retval = -EAGAIN;
else if (__dev_pm_qos_read_value(dev) < 0)
else if (__dev_pm_qos_read_value(dev) == 0)
retval = -EPERM;
else if (dev->power.runtime_status == RPM_SUSPENDED)
retval = 1;

25
drivers/base/power/sysfs.c
View file

@ -218,7 +218,14 @@ static ssize_t pm_qos_resume_latency_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
return sprintf(buf, "%d\n", dev_pm_qos_requested_resume_latency(dev));
s32 value = dev_pm_qos_requested_resume_latency(dev);
if (value == 0)
return sprintf(buf, "n/a\n");
else if (value == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
value = 0;
return sprintf(buf, "%d\n", value);
}
static ssize_t pm_qos_resume_latency_store(struct device *dev,
@ -228,11 +235,21 @@ static ssize_t pm_qos_resume_latency_store(struct device *dev,
s32 value;
int ret;
if (kstrtos32(buf, 0, &value))
return -EINVAL;
if (!kstrtos32(buf, 0, &value)) {
/*
* Prevent users from writing negative or "no constraint" values
* directly.
*/
if (value < 0 || value == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
return -EINVAL;
if (value < 0)
if (value == 0)
value = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
} else if (!strcmp(buf, "n/a") || !strcmp(buf, "n/a\n")) {
value = 0;
} else {
return -EINVAL;
}
ret = dev_pm_qos_update_request(dev->power.qos->resume_latency_req,
value);

4
drivers/cpuidle/governors/menu.c
View file

@ -298,8 +298,8 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
data->needs_update = 0;
}
/* resume_latency is 0 means no restriction */
if (resume_latency && resume_latency < latency_req)
if (resume_latency < latency_req &&
resume_latency != PM_QOS_RESUME_LATENCY_NO_CONSTRAINT)
latency_req = resume_latency;
/* Special case when user has set very strict latency requirement */

5
include/linux/pm_qos.h
View file

@ -27,16 +27,17 @@ enum pm_qos_flags_status {
PM_QOS_FLAGS_ALL,
};
#define PM_QOS_DEFAULT_VALUE -1
#define PM_QOS_DEFAULT_VALUE (-1)
#define PM_QOS_LATENCY_ANY S32_MAX
#define PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE (2000 * USEC_PER_SEC)
#define PM_QOS_NETWORK_LAT_DEFAULT_VALUE (2000 * USEC_PER_SEC)
#define PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE 0
#define PM_QOS_MEMORY_BANDWIDTH_DEFAULT_VALUE 0
#define PM_QOS_RESUME_LATENCY_DEFAULT_VALUE 0
#define PM_QOS_RESUME_LATENCY_NO_CONSTRAINT PM_QOS_LATENCY_ANY
#define PM_QOS_LATENCY_TOLERANCE_DEFAULT_VALUE 0
#define PM_QOS_LATENCY_TOLERANCE_NO_CONSTRAINT (-1)
#define PM_QOS_LATENCY_ANY ((s32)(~(__u32)0 >> 1))
#define PM_QOS_FLAG_NO_POWER_OFF (1 << 0)
#define PM_QOS_FLAG_REMOTE_WAKEUP (1 << 1)