igb_uio: fix refcount if open returns error

This fixes the problem of reference count leak if
igbuio_pci_enable_interrupts fails.

Also, replace mutex and integer with a kernel atomic counter.
This is standard pattern for kernel devices.

Fixes: 19685d5aa79c ("igb_uio: allow multi-process access")
Cc: stable@dpdk.org
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>

diff --git a/kernel/linux/igb_uio/igb_uio.c b/kernel/linux/igb_uio/igb_uio.c
index 3398eac..fede66c 100644 (file)
--- a/kernel/linux/igb_uio/igb_uio.c
+++ b/kernel/linux/igb_uio/igb_uio.c
@@ -26,8 +26,7 @@ struct rte_uio_pci_dev {
        struct uio_info info;
        struct pci_dev *pdev;
        enum rte_intr_mode mode;
-       struct mutex lock;
-       int refcnt;
+       atomic_t refcnt;
 };
 
 static int wc_activate;
@@ -320,23 +319,19 @@ igbuio_pci_open(struct uio_info *info, struct inode *inode)
        struct pci_dev *dev = udev->pdev;
        int err;
 
-       mutex_lock(&udev->lock);
-       if (++udev->refcnt > 1) {
-               mutex_unlock(&udev->lock);
+       if (atomic_inc_return(&udev->refcnt) != 1)
                return 0;
-       }
 
        /* set bus master, which was cleared by the reset function */
        pci_set_master(dev);
 
        /* enable interrupts */
        err = igbuio_pci_enable_interrupts(udev);
-       mutex_unlock(&udev->lock);
        if (err) {
+               atomic_dec(&udev->refcnt);
                dev_err(&dev->dev, "Enable interrupt fails\n");
-               return err;
        }
-       return 0;
+       return err;
 }
 
 static int
@@ -345,19 +340,14 @@ igbuio_pci_release(struct uio_info *info, struct inode *inode)
        struct rte_uio_pci_dev *udev = info->priv;
        struct pci_dev *dev = udev->pdev;
 
-       mutex_lock(&udev->lock);
-       if (--udev->refcnt > 0) {
-               mutex_unlock(&udev->lock);
-               return 0;
-       }
-
-       /* disable interrupts */
-       igbuio_pci_disable_interrupts(udev);
+       if (atomic_dec_and_test(&udev->refcnt)) {
+               /* disable interrupts */
+               igbuio_pci_disable_interrupts(udev);
 
-       /* stop the device from further DMA */
-       pci_clear_master(dev);
+               /* stop the device from further DMA */
+               pci_clear_master(dev);
+       }
 
-       mutex_unlock(&udev->lock);
        return 0;
 }
 
@@ -489,7 +479,6 @@ igbuio_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
        if (!udev)
                return -ENOMEM;
 
-       mutex_init(&udev->lock);
        /*
         * enable device: ask low-level code to enable I/O and
         * memory
@@ -529,6 +518,7 @@ igbuio_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
        udev->info.release = igbuio_pci_release;
        udev->info.priv = udev;
        udev->pdev = dev;
+       atomic_set(&udev->refcnt, 0);
 
        err = sysfs_create_group(&dev->dev.kobj, &dev_attr_grp);
        if (err != 0)
@@ -580,7 +570,6 @@ igbuio_pci_remove(struct pci_dev *dev)
 {
        struct rte_uio_pci_dev *udev = pci_get_drvdata(dev);
 
-       mutex_destroy(&udev->lock);
        sysfs_remove_group(&dev->dev.kobj, &dev_attr_grp);
        uio_unregister_device(&udev->info);
        igbuio_pci_release_iomem(&udev->info);