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? > + > return error; > } > EXPORT_SYMBOL_GPL(__pm_runtime_set_status); > Other than the above comment, this looks good to me. Kind regards Uffe