diff mbox series

soundwire: bus: Fix unbalanced pm_runtime_put() causing usage count underflow

Message ID 20230227112933.1593997-1-rf@opensource.cirrus.com
State New
Headers
Series soundwire: bus: Fix unbalanced pm_runtime_put() causing usage count underflow |

Commit Message

Richard Fitzgerald Feb. 27, 2023, 11:29 a.m. UTC 
  This reverts commit
443a98e649b4 ("soundwire: bus: use pm_runtime_resume_and_get()")

Change calls to pm_runtime_resume_and_get() back to pm_runtime_get_sync().
This fixes a usage count underrun caused by doing a pm_runtime_put() even
though pm_runtime_resume_and_get() returned an error.

The three affected functions ignore -EACCES error from trying to get
pm_runtime, and carry on, including a put at the end of the function.
But pm_runtime_resume_and_get() does not increment the usage count if it
returns an error. So in the -EACCES case you must not call
pm_runtime_put().

The documentation for pm_runtime_get_sync() says:
 "Consider using pm_runtime_resume_and_get() ...  as this is likely to
 result in cleaner code."

In this case I don't think it results in cleaner code because the
pm_runtime_put() at the end of the function would have to be conditional on
the return value from pm_runtime_resume_and_get() at the top of the
function.

pm_runtime_get_sync() doesn't have this problem because it always
increments the count, so always needs a put. The code can just flow through
and do the pm_runtime_put() unconditionally.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
---
 drivers/soundwire/bus.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

Comments

Pierre-Louis Bossart Feb. 27, 2023, 3:27 p.m. UTC | #1 
On 2/27/23 06:29, Richard Fitzgerald wrote:
> This reverts commit
> 443a98e649b4 ("soundwire: bus: use pm_runtime_resume_and_get()")
> 
> Change calls to pm_runtime_resume_and_get() back to pm_runtime_get_sync().
> This fixes a usage count underrun caused by doing a pm_runtime_put() even
> though pm_runtime_resume_and_get() returned an error.
> 
> The three affected functions ignore -EACCES error from trying to get
> pm_runtime, and carry on, including a put at the end of the function.
> But pm_runtime_resume_and_get() does not increment the usage count if it
> returns an error. So in the -EACCES case you must not call
> pm_runtime_put().
> 
> The documentation for pm_runtime_get_sync() says:
>  "Consider using pm_runtime_resume_and_get() ...  as this is likely to
>  result in cleaner code."
> 
> In this case I don't think it results in cleaner code because the
> pm_runtime_put() at the end of the function would have to be conditional on
> the return value from pm_runtime_resume_and_get() at the top of the
> function.
> 
> pm_runtime_get_sync() doesn't have this problem because it always
> increments the count, so always needs a put. The code can just flow through
> and do the pm_runtime_put() unconditionally.
> 
> Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>

Agreed, in hindsight the move to use pm_runtime_resume_and_get() mostly
added issues left and right with limited benefits - just too hard to
review and figure out what cases work and which ones don't.

Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>



> ---
>  drivers/soundwire/bus.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
> index 76515c33e639..4fd221d0cc81 100644
> --- a/drivers/soundwire/bus.c
> +++ b/drivers/soundwire/bus.c
> @@ -571,9 +571,11 @@ int sdw_nread(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
>  {
>  	int ret;
>  
> -	ret = pm_runtime_resume_and_get(&slave->dev);
> -	if (ret < 0 && ret != -EACCES)
> +	ret = pm_runtime_get_sync(&slave->dev);
> +	if (ret < 0 && ret != -EACCES) {
> +		pm_runtime_put_noidle(&slave->dev);
>  		return ret;
> +	}
>  
>  	ret = sdw_nread_no_pm(slave, addr, count, val);
>  
> @@ -595,9 +597,11 @@ int sdw_nwrite(struct sdw_slave *slave, u32 addr, size_t count, const u8 *val)
>  {
>  	int ret;
>  
> -	ret = pm_runtime_resume_and_get(&slave->dev);
> -	if (ret < 0 && ret != -EACCES)
> +	ret = pm_runtime_get_sync(&slave->dev);
> +	if (ret < 0 && ret != -EACCES) {
> +		pm_runtime_put_noidle(&slave->dev);
>  		return ret;
> +	}
>  
>  	ret = sdw_nwrite_no_pm(slave, addr, count, val);
>  
> @@ -1565,9 +1569,10 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave)
>  
>  	sdw_modify_slave_status(slave, SDW_SLAVE_ALERT);
>  
> -	ret = pm_runtime_resume_and_get(&slave->dev);
> +	ret = pm_runtime_get_sync(&slave->dev);
>  	if (ret < 0 && ret != -EACCES) {
>  		dev_err(&slave->dev, "Failed to resume device: %d\n", ret);
> +		pm_runtime_put_noidle(&slave->dev);
>  		return ret;
>  	}
>
diff mbox series

Patch

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index 76515c33e639..4fd221d0cc81 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -571,9 +571,11 @@  int sdw_nread(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
 {
 	int ret;
 
-	ret = pm_runtime_resume_and_get(&slave->dev);
-	if (ret < 0 && ret != -EACCES)
+	ret = pm_runtime_get_sync(&slave->dev);
+	if (ret < 0 && ret != -EACCES) {
+		pm_runtime_put_noidle(&slave->dev);
 		return ret;
+	}
 
 	ret = sdw_nread_no_pm(slave, addr, count, val);
 
@@ -595,9 +597,11 @@  int sdw_nwrite(struct sdw_slave *slave, u32 addr, size_t count, const u8 *val)
 {
 	int ret;
 
-	ret = pm_runtime_resume_and_get(&slave->dev);
-	if (ret < 0 && ret != -EACCES)
+	ret = pm_runtime_get_sync(&slave->dev);
+	if (ret < 0 && ret != -EACCES) {
+		pm_runtime_put_noidle(&slave->dev);
 		return ret;
+	}
 
 	ret = sdw_nwrite_no_pm(slave, addr, count, val);
 
@@ -1565,9 +1569,10 @@  static int sdw_handle_slave_alerts(struct sdw_slave *slave)
 
 	sdw_modify_slave_status(slave, SDW_SLAVE_ALERT);
 
-	ret = pm_runtime_resume_and_get(&slave->dev);
+	ret = pm_runtime_get_sync(&slave->dev);
 	if (ret < 0 && ret != -EACCES) {
 		dev_err(&slave->dev, "Failed to resume device: %d\n", ret);
+		pm_runtime_put_noidle(&slave->dev);
 		return ret;
 	}