PCI: hv: Only queue new work items in hv_pci_devices_present() if necessary

If there is pending work in hv_pci_devices_present() we just need to add
the new dr entry into the dr_list. Add a check to detect pending work
items and update the code to skip queuing work if pending work items
are detected.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
[lorenzo.pieralisi@arm.com: updated commit log]
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.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>

1 files changed, 13 insertions, 2 deletions

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index 0dc2ecdbbe45..50cdefe3f6d3 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -1789,6 +1789,7 @@ static void hv_pci_devices_present(struct hv_pcibus_device *hbus,
         struct hv_dr_state *dr;
         struct hv_dr_work *dr_wrk;
         unsigned long flags;
+        bool pending_dr;
 
         dr_wrk = kzalloc(sizeof(*dr_wrk), GFP_NOWAIT);
         if (!dr_wrk)
@@ -1812,11 +1813,21 @@ static void hv_pci_devices_present(struct hv_pcibus_device *hbus,
         }
 
         spin_lock_irqsave(&hbus->device_list_lock, flags);
+        /*
+         * If pending_dr is true, we have already queued a work,
+         * which will see the new dr. Otherwise, we need to
+         * queue a new work.
+         */
+        pending_dr = !list_empty(&hbus->dr_list);
         list_add_tail(&dr->list_entry, &hbus->dr_list);
         spin_unlock_irqrestore(&hbus->device_list_lock, flags);
 
-        get_hvpcibus(hbus);
-        queue_work(hbus->wq, &dr_wrk->wrk);
+        if (pending_dr) {
+                kfree(dr_wrk);
+        } else {
+                get_hvpcibus(hbus);
+                queue_work(hbus->wq, &dr_wrk->wrk);
+        }
 }
 
 /**