lkml.org 
[lkml]   [2008]   [Nov]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 3/4] add ksm kernel shared memory driver
    On Wed, 12 Nov 2008 00:17:39 +0200
    Izik Eidus <ieidus@redhat.com> wrote:

    > >> +static int ksm_dev_open(struct inode *inode, struct file *filp)
    > >> +{
    > >> + try_module_get(THIS_MODULE);
    > >> + return 0;
    > >> +}
    > >> +
    > >> +static int ksm_dev_release(struct inode *inode, struct file *filp)
    > >> +{
    > >> + module_put(THIS_MODULE);
    > >> + return 0;
    > >> +}
    > >> +
    > >> +static struct file_operations ksm_chardev_ops = {
    > >> + .open = ksm_dev_open,
    > >> + .release = ksm_dev_release,
    > >> + .unlocked_ioctl = ksm_dev_ioctl,
    > >> + .compat_ioctl = ksm_dev_ioctl,
    > >> +};
    > >>
    > >
    > > Why do you roll your own module reference counting? Is there a
    > > reason you don't just set .owner and let the VFS handle it?
    > >
    >
    > Yes, I am taking get_task_mm() if the module will be removed before i
    > free the mms, things will go wrong

    But...if you set .owner, the VFS will do the try_module_get() *before*
    calling into your module (as an added bonus, it will actually check the
    return value too). All you've succeeded in doing here is adding a
    microscopic race to the module reference counting; otherwise the end
    result is the same.

    jon


    \
     
     \ /
      Last update: 2008-11-11 23:29    [W:0.024 / U:120.920 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site