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    Subject[PATCH v3 4/6] PCI: hv: remove hbus->enum_sem
    Date
    Since we serialize the present/eject work items now, we don't need the
    semaphore any more.

    This is suggested by Michael Kelley.

    Signed-off-by: Dexuan Cui <decui@microsoft.com>
    Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
    Cc: Jack Morgenstein <jackm@mellanox.com>
    Cc: stable@vger.kernel.org
    Cc: Stephen Hemminger <sthemmin@microsoft.com>
    Cc: K. Y. Srinivasan <kys@microsoft.com>
    Cc: Michael Kelley (EOSG) <Michael.H.Kelley@microsoft.com>
    ---
    drivers/pci/host/pci-hyperv.c | 17 ++---------------
    1 file changed, 2 insertions(+), 15 deletions(-)

    diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
    index aaee41faf55f..3a385212f666 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;
    @@ -1592,12 +1591,8 @@ 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)
    {
    @@ -1618,11 +1613,6 @@ 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)) {
    @@ -1639,7 +1629,6 @@ 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;
    }
    @@ -1726,7 +1715,6 @@ static void pci_devices_present_work(struct work_struct *work)
    break;
    }

    - up(&hbus->enum_sem);
    put_hvpcibus(hbus);
    kfree(dr);
    }
    @@ -2460,7 +2448,6 @@ 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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