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

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Date:   Tue, 6 Mar 2018 18:21:55 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "apw@...onical.com" <apw@...onical.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "driverdev-devel@...uxdriverproject.org" 
        <driverdev-devel@...uxdriverproject.org>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "marcelo.cerri@...onical.com" <marcelo.cerri@...onical.com>,
        "Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Jack Morgenstein <jackm@...lanox.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: [PATCH v3 5/6] PCI: hv: hv_pci_devices_present(): only queue a new
 work when necessary

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@...rosoft.com>
Cc: Vitaly Kuznetsov <vkuznets@...hat.com>
Cc: Jack Morgenstein <jackm@...lanox.com>
Cc: stable@...r.kernel.org
Cc: Stephen Hemminger <sthemmin@...rosoft.com>
Cc: K. Y. Srinivasan <kys@...rosoft.com>
Cc: Michael Kelley (EOSG) <Michael.H.Kelley@...rosoft.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