| Message ID | 1527150816-8459-1-git-send-email-ulf.hansson@linaro.org |
|---|---|
| State | Accepted |
| Commit | a0504aecba76baa1cddbc23512eb8be14df74cef |
| Headers | show |
| Series | PM / runtime: Drop usage count for suppliers at device link removal | expand |
On Thu, May 24, 2018 at 10:33 AM, Ulf Hansson <ulf.hansson@linaro.org> wrote: > In the case consumer device is runtime resumed, while the link to the > supplier is removed, the earlier call to pm_runtime_get_sync() made from > rpm_get_suppliers() does not get properly balanced with a corresponding > call to pm_runtime_put(). This leads to that suppliers remains to be > runtime resumed forever, while they don't need to. > > Let's fix the behaviour by calling rpm_put_suppliers() when dropping a > device link. Not that, since rpm_put_suppliers() checks the > link->rpm_active flag, we can correctly avoid to call pm_runtime_put() in > cases when we shouldn't. > > Reported-by: Todor Tomov <todor.tomov@linaro.org> > Fixes: 21d5c57b3726 ("PM / runtime: Use device links") > Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org> > --- > > Rafael, I am not sure if this is safe from locking point of view. The device > link write lock has been taken when pm_runtime_drop_link() is called, hence I > assume calling rpm_put_suppliers() should be fine!? If not, can you please > advise how to change? Holding the lock should be sufficient for the list to be stable, so AFAICS it is OK. Thanks, Rafael
On Sunday, May 27, 2018 12:18:05 PM CEST Rafael J. Wysocki wrote: > On Thu, May 24, 2018 at 10:33 AM, Ulf Hansson <ulf.hansson@linaro.org> wrote: > > In the case consumer device is runtime resumed, while the link to the > > supplier is removed, the earlier call to pm_runtime_get_sync() made from > > rpm_get_suppliers() does not get properly balanced with a corresponding > > call to pm_runtime_put(). This leads to that suppliers remains to be > > runtime resumed forever, while they don't need to. > > > > Let's fix the behaviour by calling rpm_put_suppliers() when dropping a > > device link. Not that, since rpm_put_suppliers() checks the > > link->rpm_active flag, we can correctly avoid to call pm_runtime_put() in > > cases when we shouldn't. > > > > Reported-by: Todor Tomov <todor.tomov@linaro.org> > > Fixes: 21d5c57b3726 ("PM / runtime: Use device links") > > Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org> > > --- > > > > Rafael, I am not sure if this is safe from locking point of view. The device > > link write lock has been taken when pm_runtime_drop_link() is called, hence I > > assume calling rpm_put_suppliers() should be fine!? If not, can you please > > advise how to change? > > Holding the lock should be sufficient for the list to be stable, so > AFAICS it is OK. So the patch has been applied, thanks!
diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 8bef3cb..beb85c3 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -1607,6 +1607,8 @@ void pm_runtime_new_link(struct device *dev) void pm_runtime_drop_link(struct device *dev) { + rpm_put_suppliers(dev); + spin_lock_irq(&dev->power.lock); WARN_ON(dev->power.links_count == 0); dev->power.links_count--;
In the case consumer device is runtime resumed, while the link to the supplier is removed, the earlier call to pm_runtime_get_sync() made from rpm_get_suppliers() does not get properly balanced with a corresponding call to pm_runtime_put(). This leads to that suppliers remains to be runtime resumed forever, while they don't need to. Let's fix the behaviour by calling rpm_put_suppliers() when dropping a device link. Not that, since rpm_put_suppliers() checks the link->rpm_active flag, we can correctly avoid to call pm_runtime_put() in cases when we shouldn't. Reported-by: Todor Tomov <todor.tomov@linaro.org> Fixes: 21d5c57b3726 ("PM / runtime: Use device links") Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org> --- Rafael, I am not sure if this is safe from locking point of view. The device link write lock has been taken when pm_runtime_drop_link() is called, hence I assume calling rpm_put_suppliers() should be fine!? If not, can you please advise how to change? Kind regards Uffe --- drivers/base/power/runtime.c | 2 ++ 1 file changed, 2 insertions(+) -- 2.7.4