Re: [PATCH v3 2/3] s390/pci: Rework __zpci_event_availability() to remove conditional locking

[Niklas Schnelle <schnelle@linux.ibm.com>]

On Wed, 2026-08-05 at 15:36 +0200, Heiko Carstens wrote:
> Clang's compiler based static context analysis does not work with locks
> that are conditionally taken like in __zpci_event_availability():
> 
> arch/s390/pci/pci_event.c:402:10: warning: mutex 'get_zdev_by_fid(ccdf->fid).state_lock'
>   is not held on every path through here [-Wthread-safety-analysis]
> 
> Given that code which takes locks conditionally can be considered
> suboptimal rework __zpci_event_availability() to get rid of this.
> 
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
> ---
>  arch/s390/pci/pci_event.c | 162 ++++++++++++++++++++------------------
>  1 file changed, 85 insertions(+), 77 deletions(-)
> 
> diff --git a/arch/s390/pci/pci_event.c b/arch/s390/pci/pci_event.c
> index bead4ed5d4ab..0a9eecb62bd1 100644
> --- a/arch/s390/pci/pci_event.c
> +++ b/arch/s390/pci/pci_event.c
--- snip ---
>  void zpci_event_availability(void *data)
>  {
> -	if (zpci_is_enabled())
> -		__zpci_event_availability(data);
> +	struct zpci_ccdf_avail *ccdf = data;
> +	struct zpci_dev *zdev;
> +
> +	if (!zpci_is_enabled())
> +		return;
> +	zpci_dbg(3, "avl fid:%x, fh:%x, pec:%x\n",
> +		 ccdf->fid, ccdf->fh, ccdf->pec);
> +	if (zpci_event_avail_any_device(ccdf))
> +		return;
> +	zdev = get_zdev_by_fid(ccdf->fid);
> +	if (!zdev)
> +		return zpci_event_avail_new_device(ccdf);
> +	mutex_lock(&zdev->state_lock);
> +	zpci_event_avail_existing_device(zdev, ccdf);
> +	mutex_unlock(&zdev->state_lock);
> +	zpci_zdev_put(zdev);
>  }

Thank you, this is exactly what I had in mind! And in my opinion
definitely much cleaner than even the original code.

Feel free to add:

Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>

Thanks,
Niklas