On Tue, Feb 12, 2019 at 5:18 PM Ulf Hansson <ulf.hans...@linaro.org> wrote: > > On Tue, 12 Feb 2019 at 13:10, Rafael J. Wysocki <r...@rjwysocki.net> wrote: > > > > From: Rafael J. Wysocki <rafael.j.wyso...@intel.com> > > > > Commit 4080ab083000 ("PM-runtime: Take suppliers into account in > > __pm_runtime_set_status()") introduced a race condition that may > > trigger if __pm_runtime_set_status() is used incorrectly (that is, > > if it is called when PM-runtime is enabled for the target device > > and working). > > > > In that case, if the original PM-runtime status of the device is > > RPM_SUSPENDED, a runtime resume of the device may occur after > > __pm_runtime_set_status() has dropped its power.lock spinlock > > and before deactivating its suppliers, so the suppliers may be > > deactivated while the device is PM-runtime-active which may lead > > to functional issues. > > > > To avoid that, modify __pm_runtime_set_status() to check whether > > or not PM-runtime is enabled for the device before activating its > > suppliers (if the new status is RPM_ACTIVE) and either return an > > error if that's the case or increment the device's disable_depth > > counter to prevent PM-runtime from being enabled for it while > > the remaining part of the function is running (disable_depth is > > then decremented on the way out). > > > > Fixes: 4080ab083000 ("PM-runtime: Take suppliers into account in > > __pm_runtime_set_status()") > > Signed-off-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com> > > --- > > drivers/base/power/runtime.c | 24 ++++++++++++++++++------ > > 1 file changed, 18 insertions(+), 6 deletions(-) > > > > Index: linux-pm/drivers/base/power/runtime.c > > =================================================================== > > --- linux-pm.orig/drivers/base/power/runtime.c > > +++ linux-pm/drivers/base/power/runtime.c > > @@ -1129,6 +1129,22 @@ int __pm_runtime_set_status(struct devic > > if (status != RPM_ACTIVE && status != RPM_SUSPENDED) > > return -EINVAL; > > > > + spin_lock_irq(&dev->power.lock); > > + > > + /* > > + * Prevent PM-runtime from being enabled for the device or return an > > + * error if it is enabled already and working. > > + */ > > + if (dev->power.runtime_error || dev->power.disable_depth) > > + dev->power.disable_depth++; > > + else > > + error = -EAGAIN; > > + > > + spin_unlock_irq(&dev->power.lock); > > + > > + if (error) > > + return error; > > + > > /* > > * If the new status is RPM_ACTIVE, the suppliers can be activated > > * upfront regardless of the current status, because next time > > @@ -1147,12 +1163,6 @@ int __pm_runtime_set_status(struct devic > > > > spin_lock_irq(&dev->power.lock); > > > > - if (!dev->power.runtime_error && !dev->power.disable_depth) { > > - status = dev->power.runtime_status; > > - error = -EAGAIN; > > - goto out; > > - } > > - > > if (dev->power.runtime_status == status || !parent) > > goto out_set; > > > > @@ -1205,6 +1215,8 @@ int __pm_runtime_set_status(struct devic > > device_links_read_unlock(idx); > > } > > > > + pm_runtime_enable(dev); > > pm_runtime_enable() uses spin_lock_irqsave(), rather than > spin_lock_irq() - is there a reason to why you want to allow that > here, but not earlier in the function?
Device links locking cannot be used in interrupt context.