[PATCH v3 5/6] PCI: hv: hv_pci_devices_present(): only queue a new work when necessary

Dexuan Cui
2018-03-06T18:21:55Z

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@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 | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index 3a385212f666..265ba11e53e2 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 +1757,21 @@ 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);
+ }
}

/**
--
2.7.4
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