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RE: [XEN][PATCH v6 14/19] common/device_tree: Add rwlock for dt_host
- To: Vikram Garhwal <vikram.garhwal@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Henry Wang <Henry.Wang@xxxxxxx>
- Date: Thu, 4 May 2023 04:38:26 +0000
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- Cc: "sstabellini@xxxxxxxxxx" <sstabellini@xxxxxxxxxx>, "michal.orzel@xxxxxxx" <michal.orzel@xxxxxxx>, Julien Grall <julien@xxxxxxx>
- Delivery-date: Thu, 04 May 2023 04:39:08 +0000
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- Thread-topic: [XEN][PATCH v6 14/19] common/device_tree: Add rwlock for dt_host
Hi Vikram,
> -----Original Message-----
> Subject: [XEN][PATCH v6 14/19] common/device_tree: Add rwlock for dt_host
>
> Dynamic programming ops will modify the dt_host and there might be other
> function which are browsing the dt_host at the same time. To avoid the race
> conditions, adding rwlock for browsing the dt_host during runtime.
While now I understand why you use rwlock instead of spinlock in this patch
since you explained it in replying my comment in v5 (Thanks!). I would still
suggest that you can add that kind of explanation in the commit message to
make the commit message clear to everyone that reading this patch.
>
> Signed-off-by: Vikram Garhwal <vikram.garhwal@xxxxxxx>
> ---
> xen/common/device_tree.c | 4 ++++
> xen/drivers/passthrough/device_tree.c | 18 ++++++++++++++++++
> xen/include/xen/device_tree.h | 6 ++++++
> 3 files changed, 28 insertions(+)
>
[...]
> ret = iommu_add_dt_device(dev);
> if ( ret < 0 )
> @@ -310,6 +321,8 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl,
> struct domain *d,
> printk(XENLOG_G_ERR "XEN_DOMCTL_assign_dt_device: assign
> \"%s\""
> " to dom%u failed (%d)\n",
> dt_node_full_name(dev), d->domain_id, ret);
> +
> + read_unlock(&dt_host->lock);
Since you added "read_unlock(&dt_host->lock);" before the final return,
i.e. "return ret", I don't think you need to add "read_unlock(&dt_host->lock);"
here before the break. Or am I missing something?
> break;
>
> case XEN_DOMCTL_deassign_device:
> @@ -328,11 +341,15 @@ int iommu_do_dt_domctl(struct xen_domctl
> *domctl, struct domain *d,
> break;
>
> ret = xsm_deassign_dtdevice(XSM_HOOK, d, dt_node_full_name(dev));
> +
Nit: Unnecessary blank line addition here.
Kind regards,
Henry
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