Re: [PATCH v1 2/6] dmaengine: dmatest: Fix process hang when reading 'wait' parameter

[Vinod Koul <vkoul@kernel.org>]

On 24-04-20, 19:11, Andy Shevchenko wrote:
> If we do
> 
>   % echo 1 > /sys/module/dmatest/parameters/run
>   [  115.851124] dmatest: Could not start test, no channels configured
> 
>   % echo dma8chan7 > /sys/module/dmatest/parameters/channel
>   [  127.563872] dmatest: Added 1 threads using dma8chan7
> 
>   % cat /sys/module/dmatest/parameters/wait
>   ... !!! HANG !!! ...
> 
> The culprit is the commit 6138f967bccc
> 
>   ("dmaengine: dmatest: Use fixed point div to calculate iops")
> 
> which makes threads not to run, but pending and being kicked off by writing
> to the 'run' node. However, it forgot to consider 'wait' routine to avoid
> above mentioned case.
> 
> In order to fix this, check for really running threads, i.e. with pending
> and done flags unset.
> 
> It's pity the culprit commit hadn't updated documentation and tested all
> possible scenarios.
> 
> Fixes: 6138f967bccc ("dmaengine: dmatest: Use fixed point div to calculate iops")
> Cc: Seraj Alijan <seraj.alijan@sondrel.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>  drivers/dma/dmatest.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
> index 4993e3e5c5b01..307622e765996 100644
> --- a/drivers/dma/dmatest.c
> +++ b/drivers/dma/dmatest.c
> @@ -240,7 +240,7 @@ static bool is_threaded_test_run(struct dmatest_info *info)
>  		struct dmatest_thread *thread;
>  
>  		list_for_each_entry(thread, &dtc->threads, node) {
> -			if (!thread->done)
> +			if (!thread->done && !thread->pending)
>  				return true;
>  		}
>  	}
> @@ -1192,7 +1192,7 @@ static int dmatest_chan_set(const char *val, const struct kernel_param *kp)
>  		mutex_unlock(&info->lock);
>  		return ret;
>  	}
> -	/*Clear any previously run threads */
> +	/* Clear any previously run threads */

This does not belong to this patch, can you please split it out...

-- 
~Vinod