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    SubjectRe: [GIT, RFC] Killing the Big Kernel Lock
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    On Monday 29 March 2010, Frederic Weisbecker wrote:
    > On Mon, Mar 29, 2010 at 01:18:48AM +0200, Frederic Weisbecker wrote:
    > > @@ -1943,7 +1949,7 @@ static ssize_t proc_fdinfo_read(struct file *file, char __user *buf,
    > > }
    > >
    > > static const struct file_operations proc_fdinfo_file_operations = {
    > > - .open = nonseekable_open,
    > > + .llseek = generic_file_llseek,
    > > .read = proc_fdinfo_read,
    > > };
    > >
    > >
    > > Replacing default_llseek() by generic_file_llseek() as you
    > > did for most of the other parts is fine.
    > >
    > > But the above changes the semantics as it makes it seekable.
    > > Why not just keeping it as is? It just ends up in no_llseek().

    The default is default_llseek, which uses the BKL and cannot be
    used if procfs is builtin and the BKL is a module.

    > There is also the ioctl part that takes the bkl in procfs.
    > I'll just check nothing weird happens there wrt file pos.
    > We probably first need to pushdown the bkl in the procfs
    > ioctl handlers.

    The BKL in procfs is only for proc files that have registered
    their own .ioctl instead of .unlocked_ioctl method. Converting
    every file_operations instance to provide an unlocked_ioctl
    (as one of the other patches does) makes sure that this path
    is never taken. BTW, there are less than a handful of procfs files
    that provide an ioctl operation, and those probably should never
    have been merged.

    Arnd


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