Re: [PATCH] PM / wakeup: Register wakeup class kobj after device is added
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 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
> > > #include
> > > #include
> > > +#include
> > > #include
> > > #include
> > > #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.
Re: [PATCH] PM / wakeup: Register wakeup class kobj after device is added
On Fri, Aug 16, 2019 at 2:46 PM Stephen Boyd wrote:
>
> Quoting Tri Vo (2019-08-16 14:27:35)
> > On Fri, Aug 16, 2019 at 7:56 AM Stephen Boyd 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
> > > #include
> > > #include
> > > +#include
> > > #include
> > > #include
> > > #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(>kobj,
> > >
> > > _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(>kobj, _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);
Re: [PATCH] PM / wakeup: Register wakeup class kobj after device is added
Quoting Tri Vo (2019-08-16 14:27:35)
> On Fri, Aug 16, 2019 at 7:56 AM Stephen Boyd 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
> > #include
> > #include
> > +#include
> > #include
> > #include
> > #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(>kobj,
> >
> > _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(>kobj, _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);
Re: [PATCH] PM / wakeup: Register wakeup class kobj after device is added
On Fri, Aug 16, 2019 at 7:56 AM Stephen Boyd 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
> Cc: Qian Cai
> Cc: Tri Vo
> Signed-off-by: Stephen Boyd
> ---
> 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
> #include
> #include
> +#include
> #include
> #include
> #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(>kobj,
>_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(>kobj, _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
>
[PATCH] PM / wakeup: Register wakeup class kobj after device is added
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
Cc: Qian Cai
Cc: Tri Vo
Signed-off-by: Stephen Boyd
---
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
#include
#include
+#include
#include
#include
#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(>kobj,
_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(>kobj, _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
