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Message-ID: <20250829003319.2785282-3-briannorris@chromium.org>
Date: Thu, 28 Aug 2025 17:28:28 -0700
From: Brian Norris <briannorris@...omium.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
Pavel Machek <pavel@...nel.org>
Cc: "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
kunit-dev@...glegroups.com,
Len Brown <lenb@...nel.org>,
Sakari Ailus <sakari.ailus@...ux.intel.com>,
linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org,
Brian Norris <briannorris@...omium.org>
Subject: [PATCH 3/3] PM: runtime: Update kerneldoc return codes
APIs based on __pm_runtime_idle() (pm_runtime_idle(), pm_request_idle())
do not return 1 when already suspended. They return -EAGAIN. This is
already covered in the docs, so the entry for "1" is redundant and
conflicting.
(pm_runtime_put() and pm_runtime_put_sync() were previously incorrect,
but that's fixed in "PM: runtime: pm_runtime_put{,_sync}() returns 1
when already suspended", to ensure consistency with APIs like
pm_runtime_put_autosuspend().)
RPM_GET_PUT APIs based on __pm_runtime_suspend() do return 1 when
already suspended, but the language is a little unclear -- it's not
really an "error", so it seems better to list as a clarification before
the 0/success case. Additionally, they only actually return 1 when the
refcount makes it to 0; if the usage_count is still non-zero, we return
0.
pm_runtime_put(), etc., also don't appear at first like they can ever
see "-EAGAIN: Runtime PM usage_count non-zero", because in non-racy
conditions, pm_runtime_put() would drop its reference count, see it's
non-zero, and return early (in __pm_runtime_idle()). However, it's
possible to race with another actor that increments the usage_count
afterward, since rpm_idle() is protected by a separate lock; in such a
case, we may see -EAGAIN.
Because this case is only seen in the presence of concurrent actors, it
makes sense to clarify that this is when "usage_count **became**
non-zero", by way of some racing actor.
Lastly, pm_runtime_put_sync_suspend() duplicated some -EAGAIN language.
Fix that.
Fixes: 271ff96d6066 ("PM: runtime: Document return values of suspend-related API functions")
Link: https://lore.kernel.org/linux-pm/aJ5pkEJuixTaybV4@google.com/
Signed-off-by: Brian Norris <briannorris@...omium.org>
---
include/linux/pm_runtime.h | 33 ++++++++++++++++++---------------
1 file changed, 18 insertions(+), 15 deletions(-)
diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h
index d88d6b6ccf5b..fd17ffe1bc79 100644
--- a/include/linux/pm_runtime.h
+++ b/include/linux/pm_runtime.h
@@ -356,7 +356,6 @@ static inline int pm_runtime_force_resume(struct device *dev) { return -ENXIO; }
* * -EPERM: Device PM QoS resume latency 0.
* * -EINPROGRESS: Suspend already in progress.
* * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
* Other values and conditions for the above values are possible as returned by
* Runtime PM idle and suspend callbacks.
*/
@@ -439,7 +438,6 @@ static inline int pm_runtime_resume(struct device *dev)
* * -EPERM: Device PM QoS resume latency 0.
* * -EINPROGRESS: Suspend already in progress.
* * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
*/
static inline int pm_request_idle(struct device *dev)
{
@@ -540,15 +538,16 @@ static inline int pm_runtime_resume_and_get(struct device *dev)
* equal to 0, queue up a work item for @dev like in pm_request_idle().
*
* Return:
+ * * 1: Usage counts dropped to zero, but device was already suspended.
* * 0: Success.
* * -EINVAL: Runtime PM error.
* * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero or Runtime PM status change ongoing.
+ * * -EAGAIN: Runtime PM usage_count became non-zero or Runtime PM status
+ * change ongoing.
* * -EBUSY: Runtime PM child_count non-zero.
* * -EPERM: Device PM QoS resume latency 0.
* * -EINPROGRESS: Suspend already in progress.
* * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
*/
static inline int pm_runtime_put(struct device *dev)
{
@@ -565,15 +564,16 @@ DEFINE_FREE(pm_runtime_put, struct device *, if (_T) pm_runtime_put(_T))
* equal to 0, queue up a work item for @dev like in pm_request_autosuspend().
*
* Return:
+ * * 1: Usage counts dropped to zero, but device was already suspended.
* * 0: Success.
* * -EINVAL: Runtime PM error.
* * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero or Runtime PM status change ongoing.
+ * * -EAGAIN: Runtime PM usage_count became non-zero or Runtime PM status
+ * change ongoing.
* * -EBUSY: Runtime PM child_count non-zero.
* * -EPERM: Device PM QoS resume latency 0.
* * -EINPROGRESS: Suspend already in progress.
* * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
*/
static inline int __pm_runtime_put_autosuspend(struct device *dev)
{
@@ -590,15 +590,16 @@ static inline int __pm_runtime_put_autosuspend(struct device *dev)
* in pm_request_autosuspend().
*
* Return:
+ * * 1: Usage counts dropped to zero, but device was already suspended.
* * 0: Success.
* * -EINVAL: Runtime PM error.
* * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero or Runtime PM status change ongoing.
+ * * -EAGAIN: Runtime PM usage_count became non-zero or Runtime PM status
+ * change ongoing.
* * -EBUSY: Runtime PM child_count non-zero.
* * -EPERM: Device PM QoS resume latency 0.
* * -EINPROGRESS: Suspend already in progress.
* * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
*/
static inline int pm_runtime_put_autosuspend(struct device *dev)
{
@@ -619,14 +620,15 @@ static inline int pm_runtime_put_autosuspend(struct device *dev)
* if it returns an error code.
*
* Return:
+ * * 1: Usage counts dropped to zero, but device was already suspended.
* * 0: Success.
* * -EINVAL: Runtime PM error.
* * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero or Runtime PM status change ongoing.
+ * * -EAGAIN: Runtime PM usage_count became non-zero or Runtime PM status
+ * change ongoing.
* * -EBUSY: Runtime PM child_count non-zero.
* * -EPERM: Device PM QoS resume latency 0.
* * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
* Other values and conditions for the above values are possible as returned by
* Runtime PM suspend callbacks.
*/
@@ -646,15 +648,15 @@ static inline int pm_runtime_put_sync(struct device *dev)
* if it returns an error code.
*
* Return:
+ * * 1: Usage counts dropped to zero, but device was already suspended.
* * 0: Success.
* * -EINVAL: Runtime PM error.
* * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero or Runtime PM status change ongoing.
- * * -EAGAIN: usage_count non-zero or Runtime PM status change ongoing.
+ * * -EAGAIN: Runtime PM usage_count became non-zero or Runtime PM status
+ * change ongoing.
* * -EBUSY: Runtime PM child_count non-zero.
* * -EPERM: Device PM QoS resume latency 0.
* * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
* Other values and conditions for the above values are possible as returned by
* Runtime PM suspend callbacks.
*/
@@ -677,15 +679,16 @@ static inline int pm_runtime_put_sync_suspend(struct device *dev)
* if it returns an error code.
*
* Return:
+ * * 1: Usage counts dropped to zero, but device was already suspended.
* * 0: Success.
* * -EINVAL: Runtime PM error.
* * -EACCES: Runtime PM disabled.
- * * -EAGAIN: Runtime PM usage_count non-zero or Runtime PM status change ongoing.
+ * * -EAGAIN: Runtime PM usage_count became non-zero or Runtime PM status
+ * change ongoing.
* * -EBUSY: Runtime PM child_count non-zero.
* * -EPERM: Device PM QoS resume latency 0.
* * -EINPROGRESS: Suspend already in progress.
* * -ENOSYS: CONFIG_PM not enabled.
- * * 1: Device already suspended.
* Other values and conditions for the above values are possible as returned by
* Runtime PM suspend callbacks.
*/
--
2.51.0.318.gd7df087d1a-goog
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