lkml.org 
[lkml]   [2004]   [Sep]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: f_ops flag to speed up compatible ioctls in linux kernel
From
Date
On Wed, 2004-09-01 at 03:32, viro@parcelfarce.linux.theplanet.co.uk
wrote:
> On Wed, Sep 01, 2004 at 10:22:45AM +0300, Michael S. Tsirkin wrote:
> > Hello!
> > Currently, on the x86_64 architecture, its quite tricky to make
> > a char device ioctl work for an x86 executables.
> > In particular,
> > 1. there is a requirement that ioctl number is unique -
> > which is hard to guarantee especially for out of kernel modules
>
> Too bad.
>
> > 2. there's a performance huge overhead for each compat call - there's
> > a hash lookup in a global hash inside a lock_kernel -
> > and I think compat performance *is* important.
> >
> > Further, adding a command to the ioctl suddenly requires changing
> > two places - registration code and ioctl itself.
>
> So don't add them. Adding a new ioctl is *NOT* a step to be taken lightly -
> we used to be far too accepting in that area and as somebody who'd waded
> through the resulting dungpiles over the last months I can tell you that
> result is utterly revolting.
>

By adding a new ioctl you are adding a new use of the BKL. It has been
suggested on dri-devel that this should be fixed. Is this even
possible?

Lee


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 14:05    [W:0.706 / U:0.492 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site