Re: [PATCH] iio: buffer: Fix wait_queue not being removed

["Nuno Sá" <noname.nuno@gmail.com>]

On Mon, 2026-02-23 at 17:05 +0200, Andy Shevchenko wrote:
> On Mon, Feb 23, 2026 at 01:39:37PM +0000, Nuno Sá wrote:
> > On Sun, 2026-02-22 at 12:37 +0000, Jonathan Cameron wrote:
> > > On Sat, 21 Feb 2026 15:27:42 -0600
> > > David Lechner <dlechner@baylibre.com> wrote:
> > > 
> > > > On 2/16/26 7:24 AM, Nuno Sá via B4 Relay wrote:
> > > > > From: Nuno Sá <nuno.sa@analog.com>
> > > > > 
> > > > > In the edge case where the IIO device is unregistered while we're
> > > > > buffering, we were directly returning an error without removing the wait
> > > > > queue. Instead, set 'ret' and break out of the loop.
> > > > > 
> > > > > Fixes: 9eeee3b0bf19 ("iio: Add output buffer support")
> > > > > Signed-off-by: Nuno Sá <nuno.sa@analog.com>
> > > > > ---  
> > > > Reviewed-by: David Lechner <dlechner@baylibre.com>
> > > > 
> > > This brings the code inline with the near identical
> > > flow in the read path.
> > > 
> > > It's been a while since I last looked at the locking / tear
> > > down (what that ->info check is all about).  I'll add actually
> > 
> > Yeah not sure if you remember but I already said this a couple of times. In the buffer
> > paths I'm not convinced the check we have is enough. Still very open to races AFAICT.
> > I have it in my list to try and trigger and actual issue/dump on that path so it's not just
> > theory. Already asked the bot to write some stressor/test code :).
> 
> Perhaps also a good task for stress-ng? Ask Colin!

I would be surprised if there's a stressor for this :). We need to sample (read) an IIO buffer while
unbinding the device at the same tim. It might even be that some real issues only pop for some
specific HW (which provides different buffer knobs).

- Nuno Sá

> 
> > > documenting all the corner cases to the todo list as IIRC
> > > there are some non obvious ordering constraints.  IIRC,
> > > in the buffer paths, it is fairly straight forward
> > > as it's just an optimization to avoid queuing or draining
> > > data when the device is going down - nothing about the buffers
> > > themselves involves interacting directly with the hardware.
> > > 
> > > Applied to the fixes-togreg branch of iio.git and marked
> > > for stable.
> > 
> > BTW, I just realized we now have an Assisted-by: tag for getting help from AI. I should
> > say that this bug was identified by Claude code (when bulding the stressor test app I 
> > mentioned above :)). So, maybe (or can we Reported by: Claude Code?!!):
> 
> > Assisted-by: Claude Code