Re: [PATCH 4/6] hw/scsi/virtio-scsi: Use RCU_READ macro

[Manos Pitsidianakis]

On Wed, 24 Jan 2024 09:41, Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
> Replace the manual rcu_read_(un)lock calls by the
> WITH_RCU_READ_LOCK_GUARD macro (See commit ef46ae67ba
> "docs/style: call out the use of GUARD macros").
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
> hw/scsi/virtio-scsi.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
> index 690aceec45..998227404a 100644
> --- a/hw/scsi/virtio-scsi.c
> +++ b/hw/scsi/virtio-scsi.c
> @@ -343,14 +343,14 @@ static void virtio_scsi_do_one_tmf_bh(VirtIOSCSIReq *req)
>         target = req->req.tmf.lun[1];
>         qatomic_inc(&s->resetting);
>
> -        rcu_read_lock();
> -        QTAILQ_FOREACH_RCU(kid, &s->bus.qbus.children, sibling) {
> -            SCSIDevice *d1 = SCSI_DEVICE(kid->child);
> -            if (d1->channel == 0 && d1->id == target) {
> -                device_cold_reset(&d1->qdev);
> +        WITH_RCU_READ_LOCK_GUARD() {
> +            QTAILQ_FOREACH_RCU(kid, &s->bus.qbus.children, sibling) {
> +                SCSIDevice *d1 = SCSI_DEVICE(kid->child);
> +                if (d1->channel == 0 && d1->id == target) {
> +                    device_cold_reset(&d1->qdev);
> +                }
>             }
>         }
> -        rcu_read_unlock();
>
>         qatomic_dec(&s->resetting);
>         break;
> --
> 2.41.0

Unrelated to your patch: I just noticed in hw/scsi/virtio-scsi.c, 
s->resetting is used to flag whether the bus is resetting; but there's 
no check if a resetting is taking place before starting another. Is this 
single threaded code so it's not necessary?

As for the patch:

Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>