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From:   Dexuan Cui <decui@microsoft.com>
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        "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
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        "marcelo.cerri@canonical.com" <marcelo.cerri@canonical.com>,
        "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>,
        Dexuan Cui <decui@microsoft.com>,
        Jack Morgenstein <jackm@mellanox.com>,
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Subject: [PATCH v2 4/6] PCI: hv: remove hbus->enum_sem
Thread-Topic: [PATCH v2 4/6] PCI: hv: remove hbus->enum_sem
Thread-Index: AQHTtLdHnsXJFvisFEWUranPC/7lKA==
Date:   Mon, 5 Mar 2018 19:22:19 +0000
Message-ID: <20180305192134.32207-5-decui@microsoft.com>
References: <20180305192134.32207-1-decui@microsoft.com>
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Since we serialize the present/eject work items now, we don't need the
semaphore any more.

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 | 17 ++---------------
 1 file changed, 2 insertions(+), 15 deletions(-)

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index aaee41faf55f..3a385212f666 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -447,7 +447,6 @@ struct hv_pcibus_device {
 	spinlock_t device_list_lock;	/* Protect lists below */
 	void __iomem *cfg_addr;
=20
-	struct semaphore enum_sem;
 	struct list_head resources_for_children;
=20
 	struct list_head children;
@@ -1592,12 +1591,8 @@ static struct hv_pci_dev *get_pcichild_wslot(struct =
hv_pcibus_device *hbus,
  * It must also treat the omission of a previously observed device as
  * notification that the device no longer exists.
  *
- * Note that this function is a work item, and it may not be
- * invoked in the order that it was queued.  Back to back
- * updates of the list of present devices may involve queuing
- * multiple work items, and this one may run before ones that
- * were sent later. As such, this function only does something
- * if is the last one in the queue.
+ * Note that this function is serialized with hv_eject_device_work(),
+ * because both are pushed to the ordered workqueue hbus->wq.
  */
 static void pci_devices_present_work(struct work_struct *work)
 {
@@ -1618,11 +1613,6 @@ static void pci_devices_present_work(struct work_str=
uct *work)
=20
 	INIT_LIST_HEAD(&removed);
=20
-	if (down_interruptible(&hbus->enum_sem)) {
-		put_hvpcibus(hbus);
-		return;
-	}
-
 	/* Pull this off the queue and process it if it was the last one. */
 	spin_lock_irqsave(&hbus->device_list_lock, flags);
 	while (!list_empty(&hbus->dr_list)) {
@@ -1639,7 +1629,6 @@ static void pci_devices_present_work(struct work_stru=
ct *work)
 	spin_unlock_irqrestore(&hbus->device_list_lock, flags);
=20
 	if (!dr) {
-		up(&hbus->enum_sem);
 		put_hvpcibus(hbus);
 		return;
 	}
@@ -1726,7 +1715,6 @@ static void pci_devices_present_work(struct work_stru=
ct *work)
 		break;
 	}
=20
-	up(&hbus->enum_sem);
 	put_hvpcibus(hbus);
 	kfree(dr);
 }
@@ -2460,7 +2448,6 @@ static int hv_pci_probe(struct hv_device *hdev,
 	spin_lock_init(&hbus->config_lock);
 	spin_lock_init(&hbus->device_list_lock);
 	spin_lock_init(&hbus->retarget_msi_interrupt_lock);
-	sema_init(&hbus->enum_sem, 1);
 	init_completion(&hbus->remove_event);
 	hbus->wq =3D alloc_ordered_workqueue("hv_pci_%x", 0,
 					   hbus->sysdata.domain);
--=20
2.7.4