linux-kernel - Re: [PATCH RESEND] soundwire: bus: Fix unbalanced pm_runtime

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Message-ID: <ZDaCRwU+WFqNo5iL@matsya>
Date:   Wed, 12 Apr 2023 15:34:55 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Richard Fitzgerald <rf@...nsource.cirrus.com>
Cc:     yung-chuan.liao@...ux.intel.com,
        pierre-louis.bossart@...ux.intel.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, patches@...nsource.cirrus.com
Subject: Re: [PATCH RESEND] soundwire: bus: Fix unbalanced pm_runtime_put()
 causing usage count underflow

On 06-04-23, 14:46, 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.

Applied, thanks

-- 
~Vinod