[PATCH v2 5/6] PCI: hv: hv_pci_devices_present(): only queue a new work when necessary

From: Dexuan Cui
Date: Mon Mar 05 2018 - 14:23:09 EST


If there is a pending work, we just need to add the new dr into
the dr_list.

This is suggested by Michael Kelley.

Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Cc: Jack Morgenstein <jackm@xxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Cc: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
Cc: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
Cc: Michael Kelley (EOSG) <Michael.H.Kelley@xxxxxxxxxxxxx>
---
drivers/pci/host/pci-hyperv.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index 3a385212f666..d3aa6736a9bb 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -1733,6 +1733,7 @@ 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)
@@ -1756,11 +1757,23 @@ 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);
+ }
+
+ spin_unlock_irqrestore(&hbus->device_list_lock, flags);
}

/**
--
2.7.4