Re: [PATCH V2] dmaengine: Fix client_count is countered one more incorrectly.

Vinod Koul
2022-11-04T13:27:44Z

On 02-11-22, 11:07, Jerry Snitselaar wrote:
> Hi Vinod,
>
> Thoughts on this patch?
>
> Maybe changing the summary to "dmaengine: Fix double increment of client_count in dma_chan_get()"
> would be clearer?

Yes that would be better

>
> On Sat, Oct 01, 2022 at 01:36:52AM +0800, Koba Ko wrote:
> > If the passed client_count is 0,
> > it would be incremented by balance_ref_count first
> > then increment one more.
> > This would cause client_count to 2.
> >
> > cat /sys/class/dma/dma0chan*/in_use
> > 2
> > 2
> > 2
>
> Would this be better?
>
> The first time dma_chan_get() is called for a channel the channel
> client_count is incorrectly incremented twice for public channels,
> first in balance_ref_count(), and again prior to returning. This
> results in an incorrect client count which will lead to the
> channel resources not being freed when they should be. A simple
> test of repeated module load and unload of async_tx on a Dell
> Power Edge R7425 also shows this resulting in a kref underflow
> warning.

Agree, also if you have the underflow warning handy, do add it to the
log

--
~Vinod