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SubjectRe: [PATCH v4 3/4] PCI: hv: Remove hbus->enum_sem
On Thu, Mar 15, 2018 at 02:21:51PM +0000, Dexuan Cui wrote:
> Since we serialize the present/eject work items now, we don't need the
> semaphore any more.
>
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> Reviewed-by: Michael Kelley <mikelley@microsoft.com>
> Acked-by: Haiyang Zhang <haiyangz@microsoft.com>
> Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
> Cc: Jack Morgenstein <jackm@mellanox.com>
> Cc: Stephen Hemminger <sthemmin@microsoft.com>
> Cc: K. Y. Srinivasan <kys@microsoft.com>
> ---
> drivers/pci/host/pci-hyperv.c | 17 ++---------------
> 1 file changed, 2 insertions(+), 15 deletions(-)

Dexuan,

while applying/updating these patches I notice this one may be squashed
into:

https://patchwork.ozlabs.org/patch/886266/

since they logically belong in the same patch. Are you OK with me doing
that ? Is my reading correct ?

Thanks,
Lorenzo

> diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
> index 1d2e1cb617f4..0dc2ecdbbe45 100644
> --- a/drivers/pci/host/pci-hyperv.c
> +++ b/drivers/pci/host/pci-hyperv.c
> @@ -447,7 +447,6 @@ struct hv_pcibus_device {
> spinlock_t device_list_lock; /* Protect lists below */
> void __iomem *cfg_addr;
>
> - struct semaphore enum_sem;
> struct list_head resources_for_children;
>
> struct list_head children;
> @@ -1648,12 +1647,8 @@ static struct hv_pci_dev *get_pcichild_wslot(struct hv_pcibus_device *hbus,
> * It must also treat the omission of a previously observed device as
> * notification that the device no longer exists.
> *
> - * Note that this function is a work item, and it may not be
> - * invoked in the order that it was queued. Back to back
> - * updates of the list of present devices may involve queuing
> - * multiple work items, and this one may run before ones that
> - * were sent later. As such, this function only does something
> - * if is the last one in the queue.
> + * Note that this function is serialized with hv_eject_device_work(),
> + * because both are pushed to the ordered workqueue hbus->wq.
> */
> static void pci_devices_present_work(struct work_struct *work)
> {
> @@ -1674,11 +1669,6 @@ static void pci_devices_present_work(struct work_struct *work)
>
> INIT_LIST_HEAD(&removed);
>
> - if (down_interruptible(&hbus->enum_sem)) {
> - put_hvpcibus(hbus);
> - return;
> - }
> -
> /* Pull this off the queue and process it if it was the last one. */
> spin_lock_irqsave(&hbus->device_list_lock, flags);
> while (!list_empty(&hbus->dr_list)) {
> @@ -1695,7 +1685,6 @@ static void pci_devices_present_work(struct work_struct *work)
> spin_unlock_irqrestore(&hbus->device_list_lock, flags);
>
> if (!dr) {
> - up(&hbus->enum_sem);
> put_hvpcibus(hbus);
> return;
> }
> @@ -1782,7 +1771,6 @@ static void pci_devices_present_work(struct work_struct *work)
> break;
> }
>
> - up(&hbus->enum_sem);
> put_hvpcibus(hbus);
> kfree(dr);
> }
> @@ -2516,7 +2504,6 @@ static int hv_pci_probe(struct hv_device *hdev,
> spin_lock_init(&hbus->config_lock);
> spin_lock_init(&hbus->device_list_lock);
> spin_lock_init(&hbus->retarget_msi_interrupt_lock);
> - sema_init(&hbus->enum_sem, 1);
> init_completion(&hbus->remove_event);
> hbus->wq = alloc_ordered_workqueue("hv_pci_%x", 0,
> hbus->sysdata.domain);
> --
> 2.7.4
>

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