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

BugLink: http://bugs.launchpad.net/bugs/1758378
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>
(cherry picked from commit 948373b3ed1bcf05a237c24675b84804315aff14)
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index ebfd32f142cd3f9bf15ed7f3868ed485a98ce45f..eb17036a2f32e1239dbff7d3e392291290ed6076 100644 (file)
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -1801,6 +1801,7 @@ 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)
@@ -1824,11 +1825,21 @@ 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);
+       }
 }
 
 /**