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    SubjectRe: [PATCH] uio/gen-pci: don't enable interrupts in ISR
    On Tue, Aug 09, 2011 at 02:37:43PM +0300, Michael S. Tsirkin wrote:
    > >
    > > Should I hack up a patch to remove the lock, or do you have anything in your
    > > pipeline?
    >
    >
    > Please do.
    >

    Here it is:

    Greg (and anyone else...), you can also pull this from branch "uio-for-greg" from

    git://hansjkoch.de/git/linux-hjk


    From ff74627ade002d40fe1f902b7aadab8b1f15f889 Mon Sep 17 00:00:00 2001
    From: "Hans J. Koch" <hjk@hansjkoch.de>
    Date: Tue, 9 Aug 2011 20:34:31 +0200
    Subject: [PATCH] uio: uio_pci_generic: Remove useless spin_lock

    The spin_lock in uio_pci_generic.c is only used in the interrupt
    handler, which cannot be executed twice at the same time.
    That makes the lock rather pointless. This patch removes it.

    Cc: "Michael S. Tsirkin" <mst@redhat.com>
    Cc: Chris Wright <chrisw@redhat.com>
    Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
    Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    Cc: Anthony Foiani <anthony.foiani@gmail.com>
    Reported-by: Anthony Foiani <anthony.foiani@gmail.com>
    Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    Signed-off-by: Hans J. Koch <hjk@hansjkoch.de>
    ---
    drivers/uio/uio_pci_generic.c | 5 -----
    1 files changed, 0 insertions(+), 5 deletions(-)

    diff --git a/drivers/uio/uio_pci_generic.c b/drivers/uio/uio_pci_generic.c
    index fc22e1e..02bd47b 100644
    --- a/drivers/uio/uio_pci_generic.c
    +++ b/drivers/uio/uio_pci_generic.c
    @@ -24,7 +24,6 @@
    #include <linux/pci.h>
    #include <linux/slab.h>
    #include <linux/uio_driver.h>
    -#include <linux/spinlock.h>

    #define DRIVER_VERSION "0.01.0"
    #define DRIVER_AUTHOR "Michael S. Tsirkin <mst@redhat.com>"
    @@ -33,7 +32,6 @@
    struct uio_pci_generic_dev {
    struct uio_info info;
    struct pci_dev *pdev;
    - spinlock_t lock; /* guards command register accesses */
    };

    static inline struct uio_pci_generic_dev *
    @@ -57,7 +55,6 @@ static irqreturn_t irqhandler(int irq, struct uio_info *info)
    BUILD_BUG_ON(PCI_COMMAND % 4);
    BUILD_BUG_ON(PCI_COMMAND + 2 != PCI_STATUS);

    - spin_lock_irq(&gdev->lock);
    pci_block_user_cfg_access(pdev);

    /* Read both command and status registers in a single 32-bit operation.
    @@ -83,7 +80,6 @@ static irqreturn_t irqhandler(int irq, struct uio_info *info)
    done:

    pci_unblock_user_cfg_access(pdev);
    - spin_unlock_irq(&gdev->lock);
    return ret;
    }

    @@ -158,7 +154,6 @@ static int __devinit probe(struct pci_dev *pdev,
    gdev->info.irq_flags = IRQF_SHARED;
    gdev->info.handler = irqhandler;
    gdev->pdev = pdev;
    - spin_lock_init(&gdev->lock);

    if (uio_register_device(&pdev->dev, &gdev->info))
    goto err_register;
    --
    1.7.5.4


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