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* [PATCH] PM / wakeup: Register wakeup class kobj after device is added
@ 2019-08-16 14:56 Stephen Boyd
  2019-08-16 21:27 ` Tri Vo
  0 siblings, 1 reply; 5+ messages in thread
From: Stephen Boyd @ 2019-08-16 14:56 UTC (permalink / raw)
  To: Rafael J. Wysocki; +Cc: linux-kernel, linux-pm, Qian Cai, Tri Vo

The device_set_wakeup_enable() function can be called on a device that
hasn't been registered with device_add() yet. This allows the device to
be in a state where wakeup is enabled for it but the device isn't
published to userspace in sysfs yet.

After commit 986845e747af ("PM / wakeup: Show wakeup sources stats in
sysfs"), calling device_set_wakeup_enable() will fail for a device that
hasn't been registered with the driver core via device_add(). This is
because we try to create sysfs entries for the device and associate a
wakeup class kobject with it before the device has been registered.
Let's follow a similar approach that device_set_wakeup_capable() takes
here and register the wakeup class either from
device_set_wakeup_enable() when the device is already registered, or
from dpm_sysfs_add() when the device is being registered with the driver
core via device_add().

Fixes: 986845e747af ("PM / wakeup: Show wakeup sources stats in sysfs")
Reported-by: Qian Cai <cai@lca.pw>
Cc: Qian Cai <cai@lca.pw>
Cc: Tri Vo <trong@android.com>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
---
 drivers/base/power/sysfs.c  | 10 +++++++++-
 drivers/base/power/wakeup.c | 10 ++++++----
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
index 1b9c281cbe41..27ee00f50bd7 100644
--- a/drivers/base/power/sysfs.c
+++ b/drivers/base/power/sysfs.c
@@ -5,6 +5,7 @@
 #include <linux/export.h>
 #include <linux/pm_qos.h>
 #include <linux/pm_runtime.h>
+#include <linux/pm_wakeup.h>
 #include <linux/atomic.h>
 #include <linux/jiffies.h>
 #include "power.h"
@@ -661,14 +662,21 @@ int dpm_sysfs_add(struct device *dev)
 		if (rc)
 			goto err_runtime;
 	}
+	if (dev->power.wakeup) {
+		rc = wakeup_source_sysfs_add(dev, dev->power.wakeup);
+		if (rc)
+			goto err_wakeup;
+	}
 	if (dev->power.set_latency_tolerance) {
 		rc = sysfs_merge_group(&dev->kobj,
 				       &pm_qos_latency_tolerance_attr_group);
 		if (rc)
-			goto err_wakeup;
+			goto err_wakeup_source;
 	}
 	return 0;
 
+ err_wakeup_source:
+	wakeup_source_sysfs_remove(dev->power.wakeup);
  err_wakeup:
 	sysfs_unmerge_group(&dev->kobj, &pm_wakeup_attr_group);
  err_runtime:
diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
index f7925820b5ca..5817b51d2b15 100644
--- a/drivers/base/power/wakeup.c
+++ b/drivers/base/power/wakeup.c
@@ -220,10 +220,12 @@ struct wakeup_source *wakeup_source_register(struct device *dev,
 
 	ws = wakeup_source_create(name);
 	if (ws) {
-		ret = wakeup_source_sysfs_add(dev, ws);
-		if (ret) {
-			wakeup_source_free(ws);
-			return NULL;
+		if (!dev || device_is_registered(dev)) {
+			ret = wakeup_source_sysfs_add(dev, ws);
+			if (ret) {
+				wakeup_source_free(ws);
+				return NULL;
+			}
 		}
 		wakeup_source_add(ws);
 	}
-- 
Sent by a computer through tubes


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] PM / wakeup: Register wakeup class kobj after device is added
  2019-08-16 14:56 [PATCH] PM / wakeup: Register wakeup class kobj after device is added Stephen Boyd
@ 2019-08-16 21:27 ` Tri Vo
  2019-08-16 21:46   ` Stephen Boyd
  0 siblings, 1 reply; 5+ messages in thread
From: Tri Vo @ 2019-08-16 21:27 UTC (permalink / raw)
  To: Stephen Boyd; +Cc: Rafael J. Wysocki, LKML, Linux PM, Qian Cai

On Fri, Aug 16, 2019 at 7:56 AM Stephen Boyd <swboyd@chromium.org> wrote:
>
> The device_set_wakeup_enable() function can be called on a device that
> hasn't been registered with device_add() yet. This allows the device to
> be in a state where wakeup is enabled for it but the device isn't
> published to userspace in sysfs yet.
>
> After commit 986845e747af ("PM / wakeup: Show wakeup sources stats in
> sysfs"), calling device_set_wakeup_enable() will fail for a device that
> hasn't been registered with the driver core via device_add(). This is
> because we try to create sysfs entries for the device and associate a
> wakeup class kobject with it before the device has been registered.
> Let's follow a similar approach that device_set_wakeup_capable() takes
> here and register the wakeup class either from
> device_set_wakeup_enable() when the device is already registered, or
> from dpm_sysfs_add() when the device is being registered with the driver
> core via device_add().
>
> Fixes: 986845e747af ("PM / wakeup: Show wakeup sources stats in sysfs")
> Reported-by: Qian Cai <cai@lca.pw>
> Cc: Qian Cai <cai@lca.pw>
> Cc: Tri Vo <trong@android.com>
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> ---
>  drivers/base/power/sysfs.c  | 10 +++++++++-
>  drivers/base/power/wakeup.c | 10 ++++++----
>  2 files changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
> index 1b9c281cbe41..27ee00f50bd7 100644
> --- a/drivers/base/power/sysfs.c
> +++ b/drivers/base/power/sysfs.c
> @@ -5,6 +5,7 @@
>  #include <linux/export.h>
>  #include <linux/pm_qos.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/pm_wakeup.h>
>  #include <linux/atomic.h>
>  #include <linux/jiffies.h>
>  #include "power.h"
> @@ -661,14 +662,21 @@ int dpm_sysfs_add(struct device *dev)
>                 if (rc)
>                         goto err_runtime;
>         }
> +       if (dev->power.wakeup) {

This conditional checks for the situation when wakeup source
registration have been previously attempted, but failed at
wakeup_source_sysfs_add(). My concern is that it's not easy to
understand what this check does without knowing exactly what
device_wakeup_enable() does to dev->power.wakeup before we reach this
point.

> +               rc = wakeup_source_sysfs_add(dev, dev->power.wakeup);
> +               if (rc)
> +                       goto err_wakeup;
> +       }
>         if (dev->power.set_latency_tolerance) {
>                 rc = sysfs_merge_group(&dev->kobj,
>                                        &pm_qos_latency_tolerance_attr_group);
>                 if (rc)
> -                       goto err_wakeup;
> +                       goto err_wakeup_source;
>         }
>         return 0;
>
> + err_wakeup_source:
> +       wakeup_source_sysfs_remove(dev->power.wakeup);
>   err_wakeup:
>         sysfs_unmerge_group(&dev->kobj, &pm_wakeup_attr_group);
>   err_runtime:
> diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
> index f7925820b5ca..5817b51d2b15 100644
> --- a/drivers/base/power/wakeup.c
> +++ b/drivers/base/power/wakeup.c
> @@ -220,10 +220,12 @@ struct wakeup_source *wakeup_source_register(struct device *dev,
>
>         ws = wakeup_source_create(name);
>         if (ws) {
> -               ret = wakeup_source_sysfs_add(dev, ws);
> -               if (ret) {
> -                       wakeup_source_free(ws);
> -                       return NULL;
> +               if (!dev || device_is_registered(dev)) {

Is there a possible race condition here? If dev->power.wakeup check in
dpm_sysfs_add() is done at the same time as device_is_registered(dev)
check here, then wakeup_source_sysfs_add() won't ever be called?

> +                       ret = wakeup_source_sysfs_add(dev, ws);
> +                       if (ret) {
> +                               wakeup_source_free(ws);
> +                               return NULL;
> +                       }
>                 }
>                 wakeup_source_add(ws);
>         }
> --
> Sent by a computer through tubes
>

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] PM / wakeup: Register wakeup class kobj after device is added
  2019-08-16 21:27 ` Tri Vo
@ 2019-08-16 21:46   ` Stephen Boyd
  2019-08-16 22:38     ` Tri Vo
  2019-08-19  9:36     ` Rafael J. Wysocki
  0 siblings, 2 replies; 5+ messages in thread
From: Stephen Boyd @ 2019-08-16 21:46 UTC (permalink / raw)
  To: Tri Vo; +Cc: Rafael J. Wysocki, LKML, Linux PM, Qian Cai

Quoting Tri Vo (2019-08-16 14:27:35)
> On Fri, Aug 16, 2019 at 7:56 AM Stephen Boyd <swboyd@chromium.org> wrote:
> > diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
> > index 1b9c281cbe41..27ee00f50bd7 100644
> > --- a/drivers/base/power/sysfs.c
> > +++ b/drivers/base/power/sysfs.c
> > @@ -5,6 +5,7 @@
> >  #include <linux/export.h>
> >  #include <linux/pm_qos.h>
> >  #include <linux/pm_runtime.h>
> > +#include <linux/pm_wakeup.h>
> >  #include <linux/atomic.h>
> >  #include <linux/jiffies.h>
> >  #include "power.h"
> > @@ -661,14 +662,21 @@ int dpm_sysfs_add(struct device *dev)
> >                 if (rc)
> >                         goto err_runtime;
> >         }
> > +       if (dev->power.wakeup) {
> 
> This conditional checks for the situation when wakeup source
> registration have been previously attempted, but failed at
> wakeup_source_sysfs_add(). My concern is that it's not easy to
> understand what this check does without knowing exactly what
> device_wakeup_enable() does to dev->power.wakeup before we reach this
> point.

Oh, actually this is wrong. It should be a check for
dev->power.wakeup->dev being non-NULL. That's the variable that's set by
wakeup_source_sysfs_add() upon success. So I should make it:

	if (dev->power.wakeup && !dev->power.wakeup->dev)

And there's the problem that CONFIG_PM_SLEEP could be unset. Let me fix
it up with a new inline function like device_has_wakeup_dev().

> 
> > +               rc = wakeup_source_sysfs_add(dev, dev->power.wakeup);
> > +               if (rc)
> > +                       goto err_wakeup;
> > +       }
> >         if (dev->power.set_latency_tolerance) {
> >                 rc = sysfs_merge_group(&dev->kobj,
> >                                        &pm_qos_latency_tolerance_attr_group);
> >                 if (rc)
> > -                       goto err_wakeup;
> > +                       goto err_wakeup_source;
> >         }
> >         return 0;
> >
> > + err_wakeup_source:
> > +       wakeup_source_sysfs_remove(dev->power.wakeup);
> >   err_wakeup:
> >         sysfs_unmerge_group(&dev->kobj, &pm_wakeup_attr_group);
> >   err_runtime:
> > diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
> > index f7925820b5ca..5817b51d2b15 100644
> > --- a/drivers/base/power/wakeup.c
> > +++ b/drivers/base/power/wakeup.c
> > @@ -220,10 +220,12 @@ struct wakeup_source *wakeup_source_register(struct device *dev,
> >
> >         ws = wakeup_source_create(name);
> >         if (ws) {
> > -               ret = wakeup_source_sysfs_add(dev, ws);
> > -               if (ret) {
> > -                       wakeup_source_free(ws);
> > -                       return NULL;
> > +               if (!dev || device_is_registered(dev)) {
> 
> Is there a possible race condition here? If dev->power.wakeup check in
> dpm_sysfs_add() is done at the same time as device_is_registered(dev)
> check here, then wakeup_source_sysfs_add() won't ever be called?

The same race exists for device_set_wakeup_capable() so I didn't bother
to try to avoid it. I suppose wakeup_source_sysfs_add() could run
completely, allocate the device and set the name, etc., but not call
device_add() and then we can set ws->dev and call device_add() under a
mutex so that we keep a very small window where the wakeup class is
published to sysfs. Or just throw a big mutex around the whole wakeup
class creation path so that there isn't a chance of a race. But really,
is anyone going to call device_set_wakeup_*() on a device that is also
being added to the system? Seems unlikely.

> 
> > +                       ret = wakeup_source_sysfs_add(dev, ws);
> > +                       if (ret) {
> > +                               wakeup_source_free(ws);

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] PM / wakeup: Register wakeup class kobj after device is added
  2019-08-16 21:46   ` Stephen Boyd
@ 2019-08-16 22:38     ` Tri Vo
  2019-08-19  9:36     ` Rafael J. Wysocki
  1 sibling, 0 replies; 5+ messages in thread
From: Tri Vo @ 2019-08-16 22:38 UTC (permalink / raw)
  To: Stephen Boyd; +Cc: Rafael J. Wysocki, LKML, Linux PM, Qian Cai

On Fri, Aug 16, 2019 at 2:46 PM Stephen Boyd <swboyd@chromium.org> wrote:
>
> Quoting Tri Vo (2019-08-16 14:27:35)
> > On Fri, Aug 16, 2019 at 7:56 AM Stephen Boyd <swboyd@chromium.org> wrote:
> > > diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
> > > index 1b9c281cbe41..27ee00f50bd7 100644
> > > --- a/drivers/base/power/sysfs.c
> > > +++ b/drivers/base/power/sysfs.c
> > > @@ -5,6 +5,7 @@
> > >  #include <linux/export.h>
> > >  #include <linux/pm_qos.h>
> > >  #include <linux/pm_runtime.h>
> > > +#include <linux/pm_wakeup.h>
> > >  #include <linux/atomic.h>
> > >  #include <linux/jiffies.h>
> > >  #include "power.h"
> > > @@ -661,14 +662,21 @@ int dpm_sysfs_add(struct device *dev)
> > >                 if (rc)
> > >                         goto err_runtime;
> > >         }
> > > +       if (dev->power.wakeup) {
> >
> > This conditional checks for the situation when wakeup source
> > registration have been previously attempted, but failed at
> > wakeup_source_sysfs_add(). My concern is that it's not easy to
> > understand what this check does without knowing exactly what
> > device_wakeup_enable() does to dev->power.wakeup before we reach this
> > point.
>
> Oh, actually this is wrong. It should be a check for
> dev->power.wakeup->dev being non-NULL. That's the variable that's set by
> wakeup_source_sysfs_add() upon success. So I should make it:
>
>         if (dev->power.wakeup && !dev->power.wakeup->dev)

Oh ok, this makes more sense now :)
>
> And there's the problem that CONFIG_PM_SLEEP could be unset. Let me fix
> it up with a new inline function like device_has_wakeup_dev().
>
> >
> > > +               rc = wakeup_source_sysfs_add(dev, dev->power.wakeup);
> > > +               if (rc)
> > > +                       goto err_wakeup;
> > > +       }
> > >         if (dev->power.set_latency_tolerance) {
> > >                 rc = sysfs_merge_group(&dev->kobj,
> > >                                        &pm_qos_latency_tolerance_attr_group);
> > >                 if (rc)
> > > -                       goto err_wakeup;
> > > +                       goto err_wakeup_source;
> > >         }
> > >         return 0;
> > >
> > > + err_wakeup_source:
> > > +       wakeup_source_sysfs_remove(dev->power.wakeup);
> > >   err_wakeup:
> > >         sysfs_unmerge_group(&dev->kobj, &pm_wakeup_attr_group);
> > >   err_runtime:
> > > diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
> > > index f7925820b5ca..5817b51d2b15 100644
> > > --- a/drivers/base/power/wakeup.c
> > > +++ b/drivers/base/power/wakeup.c
> > > @@ -220,10 +220,12 @@ struct wakeup_source *wakeup_source_register(struct device *dev,
> > >
> > >         ws = wakeup_source_create(name);
> > >         if (ws) {
> > > -               ret = wakeup_source_sysfs_add(dev, ws);
> > > -               if (ret) {
> > > -                       wakeup_source_free(ws);
> > > -                       return NULL;
> > > +               if (!dev || device_is_registered(dev)) {
> >
> > Is there a possible race condition here? If dev->power.wakeup check in
> > dpm_sysfs_add() is done at the same time as device_is_registered(dev)
> > check here, then wakeup_source_sysfs_add() won't ever be called?
>
> The same race exists for device_set_wakeup_capable() so I didn't bother
> to try to avoid it. I suppose wakeup_source_sysfs_add() could run
> completely, allocate the device and set the name, etc., but not call
> device_add() and then we can set ws->dev and call device_add() under a
> mutex so that we keep a very small window where the wakeup class is
> published to sysfs. Or just throw a big mutex around the whole wakeup
> class creation path so that there isn't a chance of a race. But really,
> is anyone going to call device_set_wakeup_*() on a device that is also
> being added to the system? Seems unlikely.

True. I don't have a strong opinion.
>
> >
> > > +                       ret = wakeup_source_sysfs_add(dev, ws);
> > > +                       if (ret) {
> > > +                               wakeup_source_free(ws);

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] PM / wakeup: Register wakeup class kobj after device is added
  2019-08-16 21:46   ` Stephen Boyd
  2019-08-16 22:38     ` Tri Vo
@ 2019-08-19  9:36     ` Rafael J. Wysocki
  1 sibling, 0 replies; 5+ messages in thread
From: Rafael J. Wysocki @ 2019-08-19  9:36 UTC (permalink / raw)
  To: Stephen Boyd; +Cc: Tri Vo, LKML, Linux PM, Qian Cai

On Friday, August 16, 2019 11:46:19 PM CEST Stephen Boyd wrote:
> Quoting Tri Vo (2019-08-16 14:27:35)
> > On Fri, Aug 16, 2019 at 7:56 AM Stephen Boyd <swboyd@chromium.org> wrote:
> > > diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
> > > index 1b9c281cbe41..27ee00f50bd7 100644
> > > --- a/drivers/base/power/sysfs.c
> > > +++ b/drivers/base/power/sysfs.c
> > > @@ -5,6 +5,7 @@
> > >  #include <linux/export.h>
> > >  #include <linux/pm_qos.h>
> > >  #include <linux/pm_runtime.h>
> > > +#include <linux/pm_wakeup.h>
> > >  #include <linux/atomic.h>
> > >  #include <linux/jiffies.h>
> > >  #include "power.h"
> > > @@ -661,14 +662,21 @@ int dpm_sysfs_add(struct device *dev)
> > >                 if (rc)
> > >                         goto err_runtime;
> > >         }
> > > +       if (dev->power.wakeup) {
> > 
> > This conditional checks for the situation when wakeup source
> > registration have been previously attempted, but failed at
> > wakeup_source_sysfs_add(). My concern is that it's not easy to
> > understand what this check does without knowing exactly what
> > device_wakeup_enable() does to dev->power.wakeup before we reach this
> > point.
> 
> Oh, actually this is wrong. It should be a check for
> dev->power.wakeup->dev being non-NULL. That's the variable that's set by
> wakeup_source_sysfs_add() upon success. So I should make it:
> 
> 	if (dev->power.wakeup && !dev->power.wakeup->dev)
> 
> And there's the problem that CONFIG_PM_SLEEP could be unset. Let me fix
> it up with a new inline function like device_has_wakeup_dev().

OK, fix that and resend the patch.  I'll restore the series then.




^ permalink raw reply	[flat|nested] 5+ messages in thread

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Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-08-16 14:56 [PATCH] PM / wakeup: Register wakeup class kobj after device is added Stephen Boyd
2019-08-16 21:27 ` Tri Vo
2019-08-16 21:46   ` Stephen Boyd
2019-08-16 22:38     ` Tri Vo
2019-08-19  9:36     ` Rafael J. Wysocki

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