Re: [PATCH 4.13 09/36] PM / QoS: Fix device resume latency PM QoS
From: Rafael J. Wysocki
Date: Mon Nov 06 2017 - 19:51:13 EST
On 11/6/2017 10:12 AM, Greg Kroah-Hartman wrote:
4.13-stable review patch. If anyone has any objections, please let me know.
Please drop this from the -stable queue, it has been reverted from the
mainline.
Thanks,
Rafael
------------------
From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
commit 0cc2b4e5a020fc7f4d1795741c116c983e9467d7 upstream.
The special value of 0 for device resume latency PM QoS means
"no restriction", but there are two problems with that.
First, device resume latency PM QoS requests with 0 as the
value are always put in front of requests with positive
values in the priority lists used internally by the PM QoS
framework, causing 0 to be chosen as an effective constraint
value. However, that 0 is then interpreted as "no restriction"
effectively overriding the other requests with specific
restrictions which is incorrect.
Second, the users of device resume latency PM QoS have no
way to specify that *any* resume latency at all should be
avoided, which is an artificial limitation in general.
To address these issues, modify device resume latency PM QoS to
use S32_MAX as the "no constraint" value and 0 as the "no
latency at all" one and rework its users (the cpuidle menu
governor, the genpd QoS governor and the runtime PM framework)
to follow these changes.
Also add a special "n/a" value to the corresponding user space I/F
to allow user space to indicate that it cannot accept any resume
latencies at all for the given device.
Fixes: 85dc0b8a4019 (PM / QoS: Make it possible to expose PM QoS latency constraints)
Link: https://bugzilla.kernel.org/show_bug.cgi?id=197323
Reported-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Tested-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Acked-by: Alex Shi <alex.shi@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
Documentation/ABI/testing/sysfs-devices-power | 4 +
drivers/base/cpu.c | 3 -
drivers/base/power/domain_governor.c | 53 ++++++++++++++------------
drivers/base/power/qos.c | 2
drivers/base/power/runtime.c | 2
drivers/base/power/sysfs.c | 25 ++++++++++--
drivers/cpuidle/governors/menu.c | 4 -
include/linux/pm_qos.h | 5 +-
8 files changed, 63 insertions(+), 35 deletions(-)
--- a/Documentation/ABI/testing/sysfs-devices-power
+++ b/Documentation/ABI/testing/sysfs-devices-power
@@ -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.
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -377,7 +377,8 @@ int register_cpu(struct cpu *cpu, int nu
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;
}
--- a/drivers/base/power/domain_governor.c
+++ b/drivers/base/power/domain_governor.c
@@ -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 de
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 de
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(stru
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.
--- a/drivers/base/power/qos.c
+++ b/drivers/base/power/qos.c
@@ -189,7 +189,7 @@ static int dev_pm_qos_constraints_alloca
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;
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -253,7 +253,7 @@ static int rpm_check_suspend_allowed(str
|| (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;
--- a/drivers/base/power/sysfs.c
+++ b/drivers/base/power/sysfs.c
@@ -218,7 +218,14 @@ static ssize_t pm_qos_resume_latency_sho
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_sto
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);
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -298,8 +298,8 @@ static int menu_select(struct cpuidle_dr
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 */
--- a/include/linux/pm_qos.h
+++ b/include/linux/pm_qos.h
@@ -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)