Re: [PATCH v2 4/4] pps: generators: wake up PPS_GEN_FETCHEVENT readers on unregister

[Rodolfo Giometti <giometti@enneenne.com>]

On Tue, 29 Sep 2026 07:49:37 -0500, Danish Khateeb wrote:
> A reader sleeping in PPS_GEN_FETCHEVENT waits for the next event, but
> no event comes after pps_gen_unregister_source(), so the reader sleeps
> until it gets a signal. A PPS_GEN_FETCHEVENT issued after the
> unregister sleeps the same way.
>
> Wake up the readers on unregister, and make PPS_GEN_FETCHEVENT fail
> with -ENODEV once the generator is gone, like the other ioctls. The
> wait checks info without info_lock, so clear it with WRITE_ONCE().
>
> Fixes: 86b525bed275 ("drivers pps: add PPS generators support")
> Suggested-by: Rodolfo Giometti <giometti@enneenne.com>
> Assisted-by: LLM
> Signed-off-by: Danish Khateeb <danishkhateeb03@gmail.com>
> ---
>
> Notes:
>     Tested in the same setup. With a reader asleep in PPS_GEN_FETCHEVENT,
>     unbinding the test driver used to leave it asleep until its alarm(5)
>     fired (-EINTR after 5 s), and a PPS_GEN_FETCHEVENT after the unbind
>     did the same. With this patch both return -ENODEV right away. Normal
>     use of pps_gen-dummy, including PPS_GEN_FETCHEVENT, is unchanged.
>
>  drivers/pps/generators/pps_gen.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pps/generators/pps_gen.c b/drivers/pps/generators/pps_gen.c
> index 452cc12a96f2..474e17c36458 100644
> --- a/drivers/pps/generators/pps_gen.c
> +++ b/drivers/pps/generators/pps_gen.c
> @@ -103,11 +103,14 @@ static long pps_gen_cdev_ioctl(struct file *file,
>  		dev_dbg(&pps_gen->dev, "PPS_GEN_FETCHEVENT\n");
>  
>  		ret = wait_event_interruptible(pps_gen->queue,
> -				ev != pps_gen->last_ev);
> +				ev != pps_gen->last_ev ||
> +				!READ_ONCE(pps_gen->info));
>  		if (ret == -ERESTARTSYS) {
>  			dev_dbg(&pps_gen->dev, "pending signal caught\n");
>  			return -EINTR;
>  		}
> +		if (!READ_ONCE(pps_gen->info))
> +			return -ENODEV;
>  
>  		spin_lock_irq(&pps_gen->lock);
>  		info.sequence = pps_gen->sequence;
> @@ -238,9 +241,12 @@ static void pps_gen_unregister_cdev(struct pps_gen_device *pps_gen)
>  			pps_gen->info->enable(pps_gen, false);
>  			pps_gen->enabled = false;
>  		}
> -		pps_gen->info = NULL;
> +		WRITE_ONCE(pps_gen->info, NULL);
>  	}
>  
> +	/* Wake up the readers in PPS_GEN_FETCHEVENT, they fail now as well */
> +	wake_up_interruptible_all(&pps_gen->queue);
> +
>  	put_device(&pps_gen->dev);
>  }
>  

Acked-by: Rodolfo Giometti <giometti@enneenne.com>