* [PATCH 1/2] PM-runtime: Documentation: add runtime_status ABI document
@ 2019-09-01 14:08 Akinobu Mita
2019-09-01 14:08 ` [PATCH 2/2] PM-runtime: allow userspace to monitor runtime_status changes Akinobu Mita
2019-09-01 14:23 ` [PATCH 1/2] PM-runtime: Documentation: add runtime_status ABI document Dominik Brodowski
0 siblings, 2 replies; 7+ messages in thread
From: Akinobu Mita @ 2019-09-01 14:08 UTC (permalink / raw)
To: linux-leds, linux-pm
Cc: Akinobu Mita, Alan Stern, Dominik Brodowski, Rafael J. Wysocki
/sys/devices/.../power/runtime_status is introduced by commit c92445fadb91
("PM / Runtime: Add sysfs debug files"). Then commit 0fcb4eef8294 ("PM /
Runtime: Make runtime_status attribute not debug-only (v. 2)") made the
runtime_status attribute available without CONFIG_PM_ADVANCED_DEBUG.
This adds missing runtime_status ABI document.
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
Documentation/ABI/testing/sysfs-devices-power | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-devices-power b/Documentation/ABI/testing/sysfs-devices-power
index 80a00f7..3e50536 100644
--- a/Documentation/ABI/testing/sysfs-devices-power
+++ b/Documentation/ABI/testing/sysfs-devices-power
@@ -260,3 +260,12 @@ Description:
This attribute has no effect on system-wide suspend/resume and
hibernation.
+
+What: /sys/devices/.../power/runtime_status
+Date: April 2010
+Contact: Dominik Brodowski <linux@dominikbrodowski.net>
+Description:
+ The /sys/devices/.../power/runtime_status attribute contains
+ the current runtime PM status of the device, which may be
+ "suspended", "suspending", "resuming", "active", "error" (fatal
+ error), or "unsupported" (runtime PM is disabled).
--
2.7.4
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH 2/2] PM-runtime: allow userspace to monitor runtime_status changes 2019-09-01 14:08 [PATCH 1/2] PM-runtime: Documentation: add runtime_status ABI document Akinobu Mita @ 2019-09-01 14:08 ` Akinobu Mita 2019-09-02 21:47 ` Rafael J. Wysocki 2019-09-01 14:23 ` [PATCH 1/2] PM-runtime: Documentation: add runtime_status ABI document Dominik Brodowski 1 sibling, 1 reply; 7+ messages in thread From: Akinobu Mita @ 2019-09-01 14:08 UTC (permalink / raw) To: linux-leds, linux-pm Cc: Akinobu Mita, Alan Stern, Dominik Brodowski, Rafael J. Wysocki This enables the /sys/devices/.../power/runtime_status attribute to allow the user space to get notifications via poll/select when the device runtime PM status is changed. An example use case is to avoid unnecessary accesses for device statistics (e.g. diskstats for block devices) while the device is in runtime suspend by user space LED device actitity trigger. Cc: Alan Stern <stern@rowland.harvard.edu> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> --- Documentation/ABI/testing/sysfs-devices-power | 2 ++ drivers/base/power/power.h | 1 + drivers/base/power/runtime.c | 1 + drivers/base/power/sysfs.c | 5 +++++ 4 files changed, 9 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-devices-power b/Documentation/ABI/testing/sysfs-devices-power index 3e50536..47dc357 100644 --- a/Documentation/ABI/testing/sysfs-devices-power +++ b/Documentation/ABI/testing/sysfs-devices-power @@ -269,3 +269,5 @@ Description: the current runtime PM status of the device, which may be "suspended", "suspending", "resuming", "active", "error" (fatal error), or "unsupported" (runtime PM is disabled). + This attribute allows the user space to get notifications via + poll/select when the device runtime PM status is changed. diff --git a/drivers/base/power/power.h b/drivers/base/power/power.h index ec33fbdb..8891bf4 100644 --- a/drivers/base/power/power.h +++ b/drivers/base/power/power.h @@ -74,6 +74,7 @@ extern int pm_qos_sysfs_add_flags(struct device *dev); extern void pm_qos_sysfs_remove_flags(struct device *dev); extern int pm_qos_sysfs_add_latency_tolerance(struct device *dev); extern void pm_qos_sysfs_remove_latency_tolerance(struct device *dev); +extern void sysfs_notify_runtime_status(struct device *dev); #else /* CONFIG_PM */ diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index b753355..3a3e413 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -94,6 +94,7 @@ static void __update_runtime_status(struct device *dev, enum rpm_status status) { update_pm_runtime_accounting(dev); dev->power.runtime_status = status; + sysfs_notify_runtime_status(dev); } static u64 rpm_get_accounted_time(struct device *dev, bool suspended) diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c index 1b9c281c..e86d8cb 100644 --- a/drivers/base/power/sysfs.c +++ b/drivers/base/power/sysfs.c @@ -734,3 +734,8 @@ void dpm_sysfs_remove(struct device *dev) sysfs_unmerge_group(&dev->kobj, &pm_wakeup_attr_group); sysfs_remove_group(&dev->kobj, &pm_attr_group); } + +void sysfs_notify_runtime_status(struct device *dev) +{ + sysfs_notify(&dev->kobj, "power", "runtime_status"); +} -- 2.7.4 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH 2/2] PM-runtime: allow userspace to monitor runtime_status changes 2019-09-01 14:08 ` [PATCH 2/2] PM-runtime: allow userspace to monitor runtime_status changes Akinobu Mita @ 2019-09-02 21:47 ` Rafael J. Wysocki 2019-09-03 13:13 ` Akinobu Mita 0 siblings, 1 reply; 7+ messages in thread From: Rafael J. Wysocki @ 2019-09-02 21:47 UTC (permalink / raw) To: Akinobu Mita Cc: linux-leds, Linux PM, Alan Stern, Dominik Brodowski, Rafael J. Wysocki On Sun, Sep 1, 2019 at 4:09 PM Akinobu Mita <akinobu.mita@gmail.com> wrote: > > This enables the /sys/devices/.../power/runtime_status attribute to > allow the user space to get notifications via poll/select when the device > runtime PM status is changed. > > An example use case is to avoid unnecessary accesses for device statistics > (e.g. diskstats for block devices) while the device is in runtime suspend > by user space LED device actitity trigger. > > Cc: Alan Stern <stern@rowland.harvard.edu> > Cc: Dominik Brodowski <linux@dominikbrodowski.net> > Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> > Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> > --- > Documentation/ABI/testing/sysfs-devices-power | 2 ++ > drivers/base/power/power.h | 1 + > drivers/base/power/runtime.c | 1 + > drivers/base/power/sysfs.c | 5 +++++ > 4 files changed, 9 insertions(+) > > diff --git a/Documentation/ABI/testing/sysfs-devices-power b/Documentation/ABI/testing/sysfs-devices-power > index 3e50536..47dc357 100644 > --- a/Documentation/ABI/testing/sysfs-devices-power > +++ b/Documentation/ABI/testing/sysfs-devices-power > @@ -269,3 +269,5 @@ Description: > the current runtime PM status of the device, which may be > "suspended", "suspending", "resuming", "active", "error" (fatal > error), or "unsupported" (runtime PM is disabled). > + This attribute allows the user space to get notifications via > + poll/select when the device runtime PM status is changed. > diff --git a/drivers/base/power/power.h b/drivers/base/power/power.h > index ec33fbdb..8891bf4 100644 > --- a/drivers/base/power/power.h > +++ b/drivers/base/power/power.h > @@ -74,6 +74,7 @@ extern int pm_qos_sysfs_add_flags(struct device *dev); > extern void pm_qos_sysfs_remove_flags(struct device *dev); > extern int pm_qos_sysfs_add_latency_tolerance(struct device *dev); > extern void pm_qos_sysfs_remove_latency_tolerance(struct device *dev); > +extern void sysfs_notify_runtime_status(struct device *dev); > > #else /* CONFIG_PM */ > > diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c > index b753355..3a3e413 100644 > --- a/drivers/base/power/runtime.c > +++ b/drivers/base/power/runtime.c > @@ -94,6 +94,7 @@ static void __update_runtime_status(struct device *dev, enum rpm_status status) > { > update_pm_runtime_accounting(dev); > dev->power.runtime_status = status; > + sysfs_notify_runtime_status(dev); There are concerns about this. First off, it adds overhead for devices that change the PM-runtime status relatively often. I'm not sure if that's sufficiently justified. Second, it is called for status changes from "active" to "suspending" and from "suspending" to "suspended" (and analogously for resume) which may not be particularly useful. At least, user space may not have enough time to act on such notifications. Finally, it is racy, because at the time user space does something on a device PM-runtime status change, it very well may have changed the other way around already. > } > > static u64 rpm_get_accounted_time(struct device *dev, bool suspended) > diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c > index 1b9c281c..e86d8cb 100644 > --- a/drivers/base/power/sysfs.c > +++ b/drivers/base/power/sysfs.c > @@ -734,3 +734,8 @@ void dpm_sysfs_remove(struct device *dev) > sysfs_unmerge_group(&dev->kobj, &pm_wakeup_attr_group); > sysfs_remove_group(&dev->kobj, &pm_attr_group); > } > + > +void sysfs_notify_runtime_status(struct device *dev) > +{ > + sysfs_notify(&dev->kobj, "power", "runtime_status"); > +} > -- > 2.7.4 > ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 2/2] PM-runtime: allow userspace to monitor runtime_status changes 2019-09-02 21:47 ` Rafael J. Wysocki @ 2019-09-03 13:13 ` Akinobu Mita 2019-09-03 14:31 ` Alan Stern 0 siblings, 1 reply; 7+ messages in thread From: Akinobu Mita @ 2019-09-03 13:13 UTC (permalink / raw) To: Rafael J. Wysocki Cc: linux-leds, Linux PM, Alan Stern, Dominik Brodowski, Rafael J. Wysocki 2019年9月3日(火) 6:47 Rafael J. Wysocki <rafael@kernel.org>: > > On Sun, Sep 1, 2019 at 4:09 PM Akinobu Mita <akinobu.mita@gmail.com> wrote: > > > > This enables the /sys/devices/.../power/runtime_status attribute to > > allow the user space to get notifications via poll/select when the device > > runtime PM status is changed. > > > > An example use case is to avoid unnecessary accesses for device statistics > > (e.g. diskstats for block devices) while the device is in runtime suspend > > by user space LED device actitity trigger. > > > > Cc: Alan Stern <stern@rowland.harvard.edu> > > Cc: Dominik Brodowski <linux@dominikbrodowski.net> > > Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> > > Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> > > --- > > Documentation/ABI/testing/sysfs-devices-power | 2 ++ > > drivers/base/power/power.h | 1 + > > drivers/base/power/runtime.c | 1 + > > drivers/base/power/sysfs.c | 5 +++++ > > 4 files changed, 9 insertions(+) > > > > diff --git a/Documentation/ABI/testing/sysfs-devices-power b/Documentation/ABI/testing/sysfs-devices-power > > index 3e50536..47dc357 100644 > > --- a/Documentation/ABI/testing/sysfs-devices-power > > +++ b/Documentation/ABI/testing/sysfs-devices-power > > @@ -269,3 +269,5 @@ Description: > > the current runtime PM status of the device, which may be > > "suspended", "suspending", "resuming", "active", "error" (fatal > > error), or "unsupported" (runtime PM is disabled). > > + This attribute allows the user space to get notifications via > > + poll/select when the device runtime PM status is changed. > > diff --git a/drivers/base/power/power.h b/drivers/base/power/power.h > > index ec33fbdb..8891bf4 100644 > > --- a/drivers/base/power/power.h > > +++ b/drivers/base/power/power.h > > @@ -74,6 +74,7 @@ extern int pm_qos_sysfs_add_flags(struct device *dev); > > extern void pm_qos_sysfs_remove_flags(struct device *dev); > > extern int pm_qos_sysfs_add_latency_tolerance(struct device *dev); > > extern void pm_qos_sysfs_remove_latency_tolerance(struct device *dev); > > +extern void sysfs_notify_runtime_status(struct device *dev); > > > > #else /* CONFIG_PM */ > > > > diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c > > index b753355..3a3e413 100644 > > --- a/drivers/base/power/runtime.c > > +++ b/drivers/base/power/runtime.c > > @@ -94,6 +94,7 @@ static void __update_runtime_status(struct device *dev, enum rpm_status status) > > { > > update_pm_runtime_accounting(dev); > > dev->power.runtime_status = status; > > + sysfs_notify_runtime_status(dev); > > There are concerns about this. > > First off, it adds overhead for devices that change the PM-runtime > status relatively often. I'm not sure if that's sufficiently > justified. > > Second, it is called for status changes from "active" to "suspending" > and from "suspending" to "suspended" (and analogously for resume) > which may not be particularly useful. At least, user space may not > have enough time to act on such notifications. > > Finally, it is racy, because at the time user space does something on > a device PM-runtime status change, it very well may have changed the > other way around already. I withdraw this patch now. I hope I'll retry with a real use case example program. ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 2/2] PM-runtime: allow userspace to monitor runtime_status changes 2019-09-03 13:13 ` Akinobu Mita @ 2019-09-03 14:31 ` Alan Stern 0 siblings, 0 replies; 7+ messages in thread From: Alan Stern @ 2019-09-03 14:31 UTC (permalink / raw) To: Akinobu Mita Cc: Rafael J. Wysocki, linux-leds, Linux PM, Dominik Brodowski, Rafael J. Wysocki On Tue, 3 Sep 2019, Akinobu Mita wrote: > 2019年9月3日(火) 6:47 Rafael J. Wysocki <rafael@kernel.org>: > > > > On Sun, Sep 1, 2019 at 4:09 PM Akinobu Mita <akinobu.mita@gmail.com> wrote: > > > > > > This enables the /sys/devices/.../power/runtime_status attribute to > > > allow the user space to get notifications via poll/select when the device > > > runtime PM status is changed. > > > > > > An example use case is to avoid unnecessary accesses for device statistics > > > (e.g. diskstats for block devices) while the device is in runtime suspend > > > by user space LED device actitity trigger. > > > > > > Cc: Alan Stern <stern@rowland.harvard.edu> > > > Cc: Dominik Brodowski <linux@dominikbrodowski.net> > > > Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> > > > Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> > > There are concerns about this. > > > > First off, it adds overhead for devices that change the PM-runtime > > status relatively often. I'm not sure if that's sufficiently > > justified. > > > > Second, it is called for status changes from "active" to "suspending" > > and from "suspending" to "suspended" (and analogously for resume) > > which may not be particularly useful. At least, user space may not > > have enough time to act on such notifications. > > > > Finally, it is racy, because at the time user space does something on > > a device PM-runtime status change, it very well may have changed the > > other way around already. > > I withdraw this patch now. I hope I'll retry with a real use case example > program. You might want to take a look at commit 7794f486ed0b ("usbfs: Add ioctls for runtime power management") in the usb-next branch of Greg KH's usb.git tree. It adds a mechanism for user programs to wait until a device has done a runtime resume, without races. But it is not general purpose (it applies only to USB devices), it doesn't use poll(), and it doesn't check for other kinds of runtime PM status changes. Alan Stern ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 1/2] PM-runtime: Documentation: add runtime_status ABI document 2019-09-01 14:08 [PATCH 1/2] PM-runtime: Documentation: add runtime_status ABI document Akinobu Mita 2019-09-01 14:08 ` [PATCH 2/2] PM-runtime: allow userspace to monitor runtime_status changes Akinobu Mita @ 2019-09-01 14:23 ` Dominik Brodowski 2019-09-02 21:39 ` Rafael J. Wysocki 1 sibling, 1 reply; 7+ messages in thread From: Dominik Brodowski @ 2019-09-01 14:23 UTC (permalink / raw) To: Akinobu Mita; +Cc: linux-leds, linux-pm, Alan Stern, Rafael J. Wysocki Hi! On Sun, Sep 01, 2019 at 11:08:51PM +0900, Akinobu Mita wrote: > +What: /sys/devices/.../power/runtime_status > +Date: April 2010 > +Contact: Dominik Brodowski <linux@dominikbrodowski.net> Thanks for the patch! I am not sure, however, whether I am the right contact person here -- maybe Rafael J. Wysocki as PM maintainer? Thanks, Dominik ^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 1/2] PM-runtime: Documentation: add runtime_status ABI document 2019-09-01 14:23 ` [PATCH 1/2] PM-runtime: Documentation: add runtime_status ABI document Dominik Brodowski @ 2019-09-02 21:39 ` Rafael J. Wysocki 0 siblings, 0 replies; 7+ messages in thread From: Rafael J. Wysocki @ 2019-09-02 21:39 UTC (permalink / raw) To: Dominik Brodowski, Akinobu Mita Cc: linux-leds, Linux PM, Alan Stern, Rafael J. Wysocki On Sun, Sep 1, 2019 at 4:30 PM Dominik Brodowski <linux@dominikbrodowski.net> wrote: > > Hi! > > On Sun, Sep 01, 2019 at 11:08:51PM +0900, Akinobu Mita wrote: > > +What: /sys/devices/.../power/runtime_status > > +Date: April 2010 > > +Contact: Dominik Brodowski <linux@dominikbrodowski.net> > > Thanks for the patch! I am not sure, however, whether I am the right contact > person here -- maybe Rafael J. Wysocki as PM maintainer? Right, please follow the convention used for the other attributes documented in this file. ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2019-09-03 14:31 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2019-09-01 14:08 [PATCH 1/2] PM-runtime: Documentation: add runtime_status ABI document Akinobu Mita 2019-09-01 14:08 ` [PATCH 2/2] PM-runtime: allow userspace to monitor runtime_status changes Akinobu Mita 2019-09-02 21:47 ` Rafael J. Wysocki 2019-09-03 13:13 ` Akinobu Mita 2019-09-03 14:31 ` Alan Stern 2019-09-01 14:23 ` [PATCH 1/2] PM-runtime: Documentation: add runtime_status ABI document Dominik Brodowski 2019-09-02 21:39 ` Rafael J. Wysocki
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