On Thu, 25 Feb 2021 at 19:23, Rafael J. Wysocki <r...@rjwysocki.net> wrote:
>
> From: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
>
> Because the PM-runtime status of the device is not updated in
> __rpm_callback(), attempts to suspend the suppliers of the given
> device triggered by rpm_put_suppliers() called by it may fail.
>
> Fix this by making __rpm_callback() update the device's status to
> RPM_SUSPENDED before calling rpm_put_suppliers() if the current
> status of the device is RPM_SUSPENDING and the callback just invoked
> by it has returned 0 (success).
>
> While at it, modify the code in __rpm_callback() to always check
> the device's PM-runtime status under its PM lock.
>
> Link:
> https://lore.kernel.org/linux-pm/capdykfqm06kdw_p8wxsm4dijdbho4bb6t4k50uqqvr1_cos...@mail.gmail.com/
> Fixes: 21d5c57b3726 ("PM / runtime: Use device links")
> Reported-by: elaine.zhang <zhangq...@rock-chips.com>
> Diagnosed-by: Ulf Hansson <ulf.hans...@linaro.org>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
Reviewed-by: Ulf Hansson <ulf.hans...@linaro.org>
Kind regards
Uffe
> ---
>
> v1 -> v2:
> * Initialize the "get" variable to avoid a false-positive warning from
> the compiler.
>
> ---
> drivers/base/power/runtime.c | 62
> +++++++++++++++++++++++++------------------
> 1 file changed, 37 insertions(+), 25 deletions(-)
>
> Index: linux-pm/drivers/base/power/runtime.c
> ===================================================================
> --- linux-pm.orig/drivers/base/power/runtime.c
> +++ linux-pm/drivers/base/power/runtime.c
> @@ -325,22 +325,22 @@ static void rpm_put_suppliers(struct dev
> static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
> __releases(&dev->power.lock) __acquires(&dev->power.lock)
> {
> - int retval, idx;
> bool use_links = dev->power.links_count > 0;
> + bool get = false;
> + int retval, idx;
> + bool put;
>
> if (dev->power.irq_safe) {
> spin_unlock(&dev->power.lock);
> + } else if (!use_links) {
> + spin_unlock_irq(&dev->power.lock);
> } else {
> + get = dev->power.runtime_status == RPM_RESUMING;
> +
> spin_unlock_irq(&dev->power.lock);
>
> - /*
> - * Resume suppliers if necessary.
> - *
> - * The device's runtime PM status cannot change until this
> - * routine returns, so it is safe to read the status outside
> of
> - * the lock.
> - */
> - if (use_links && dev->power.runtime_status == RPM_RESUMING) {
> + /* Resume suppliers if necessary. */
> + if (get) {
> idx = device_links_read_lock();
>
> retval = rpm_get_suppliers(dev);
> @@ -355,24 +355,36 @@ static int __rpm_callback(int (*cb)(stru
>
> if (dev->power.irq_safe) {
> spin_lock(&dev->power.lock);
> - } else {
> - /*
> - * If the device is suspending and the callback has returned
> - * success, drop the usage counters of the suppliers that have
> - * been reference counted on its resume.
> - *
> - * Do that if resume fails too.
> - */
> - if (use_links
> - && ((dev->power.runtime_status == RPM_SUSPENDING &&
> !retval)
> - || (dev->power.runtime_status == RPM_RESUMING &&
> retval))) {
> - idx = device_links_read_lock();
> + return retval;
> + }
>
> - fail:
> - rpm_put_suppliers(dev);
> + spin_lock_irq(&dev->power.lock);
>
> - device_links_read_unlock(idx);
> - }
> + if (!use_links)
> + return retval;
> +
> + /*
> + * If the device is suspending and the callback has returned success,
> + * drop the usage counters of the suppliers that have been reference
> + * counted on its resume.
> + *
> + * Do that if the resume fails too.
> + */
> + put = dev->power.runtime_status == RPM_SUSPENDING && !retval;
> + if (put)
> + __update_runtime_status(dev, RPM_SUSPENDED);
> + else
> + put = get && retval;
> +
> + if (put) {
> + spin_unlock_irq(&dev->power.lock);
> +
> + idx = device_links_read_lock();
> +
> +fail:
> + rpm_put_suppliers(dev);
> +
> + device_links_read_unlock(idx);
>
> spin_lock_irq(&dev->power.lock);
> }
>
>
>
