On Tue, Oct 5, 2021 at 6:14 PM John Keeping <john@xxxxxxxxxxxx> wrote:
>
> With PREEMPT_RT spin_unlock() is identical to spin_unlock_irq() so there
> is no reason to have a special case using the former. Furthermore,
> spin_unlock() enables preemption meaning that a task in RESUMING or
> SUSPENDING state may be preempted by a higher priority task running
> pm_runtime_get_sync() leading to a livelock.
>
> Use the non-irq_safe path for all waiting so that the waiting task will
> block.
>
> Note that this changes only the waiting behaviour of irq_safe, other
> uses are left unchanged so that the parent device always remains active
> in the same way as !RT.
>
> Signed-off-by: John Keeping <john@xxxxxxxxxxxx>
So basically, the idea is that the irq_safe flag should have no effect
when CONFIG_PREEMPT_RT is set, right?
Wouldn't it be cleaner to make it not present at all in that case?
> ---
> drivers/base/power/runtime.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
> index 96972d5f6ef3..5e0d349fab4e 100644
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -347,8 +347,9 @@ static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
> {
> int retval = 0, idx;
> bool use_links = dev->power.links_count > 0;
> + bool irq_safe = dev->power.irq_safe && !IS_ENABLED(CONFIG_PREEMPT_RT);
>
> - if (dev->power.irq_safe) {
> + if (irq_safe) {
> spin_unlock(&dev->power.lock);
> } else {
> spin_unlock_irq(&dev->power.lock);
> @@ -376,7 +377,7 @@ static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
> if (cb)
> retval = cb(dev);
>
> - if (dev->power.irq_safe) {
> + if (irq_safe) {
> spin_lock(&dev->power.lock);
> } else {
> /*
> @@ -596,7 +597,7 @@ static int rpm_suspend(struct device *dev, int rpmflags)
> goto out;
> }
>
> - if (dev->power.irq_safe) {
> + if (dev->power.irq_safe && !IS_ENABLED(CONFIG_PREEMPT_RT)) {
> spin_unlock(&dev->power.lock);
>
> cpu_relax();
> @@ -777,7 +778,7 @@ static int rpm_resume(struct device *dev, int rpmflags)
> goto out;
> }
>
> - if (dev->power.irq_safe) {
> + if (dev->power.irq_safe && !IS_ENABLED(CONFIG_PREEMPT_RT)) {
> spin_unlock(&dev->power.lock);
>
> cpu_relax();
> --
> 2.33.0
>
