2001-03-02 10:57:25

by Tigran Aivazian

Subject: [patch-2.4.2-ac8] misc_register() fix (was Re: Linux 2.4.2ac8

On Fri, 2 Mar 2001, Tigran Aivazian wrote:
> On Thu, 1 Mar 2001, Alan Cox wrote:
> > 2.4.2-ac8
> > o Stop two people claiming the same misc dev id (Philipp Rumpf)
>
> is this what has broken misc devi registration on my machine? I have two
> misc devices -- microcode and psaux -- now (ac8) I get none, /proc/misc is
> empty. Also, on boot gpm generates an "oops" from gpm.c(968) saying
> "/dev/mouse: No such device"

Hi Alan,

here is the fix, tested, it works fine. The only unsatisfactory thing is
that we do an extra if() on each iteration making misc_register()
typically a few instructions slower. I will think a few minutes on how to
make the old version work (i.e. I suspect it was just an incorrect walking
of the misc_list in ac8).

Regards,
Tigran

--- linux/drivers/char/misc.c.0 Fri Mar 2 09:35:01 2001
+++ linux/drivers/char/misc.c Fri Mar 2 10:01:17 2001
@@ -175,14 +175,16 @@

if (misc->next || misc->prev)
return -EBUSY;
+
down(&misc_sem);
- c = misc_list.next;

- while ((c != &misc_list) && (c->minor != misc->minor))
+ c = misc_list.next;
+ while (c != &misc_list) {
+ if (c->minor == misc->minor) {
+ up(&misc_sem);
+ return -EBUSY;
+ }
c = c->next;
- if (c == &misc_list) {
- up(&misc_sem);
- return -EBUSY;
}

if (misc->minor == MISC_DYNAMIC_MINOR) {

2001-03-02 11:04:05

by Philipp Rumpf

Subject: Re: [patch-2.4.2-ac8] misc_register() fix (was Re: Linux 2.4.2ac8

On Fri, Mar 02, 2001 at 10:55:39AM +0000, Tigran Aivazian wrote:
> On Fri, 2 Mar 2001, Tigran Aivazian wrote:
> > On Thu, 1 Mar 2001, Alan Cox wrote:
> > > 2.4.2-ac8
> > > o Stop two people claiming the same misc dev id (Philipp Rumpf)
> >
> > is this what has broken misc devi registration on my machine? I have two
> > misc devices -- microcode and psaux -- now (ac8) I get none, /proc/misc is
> > empty. Also, on boot gpm generates an "oops" from gpm.c(968) saying
> > "/dev/mouse: No such device"
>
> Hi Alan,
>
> here is the fix, tested, it works fine. The only unsatisfactory thing is
> that we do an extra if() on each iteration making misc_register()
> typically a few instructions slower. I will think a few minutes on how to
> make the old version work (i.e. I suspect it was just an incorrect walking
> of the misc_list in ac8).

See earlier patch.

> --- linux/drivers/char/misc.c.0 Fri Mar 2 09:35:01 2001
> +++ linux/drivers/char/misc.c Fri Mar 2 10:01:17 2001
> @@ -175,14 +175,16 @@
>
> if (misc->next || misc->prev)
> return -EBUSY;
> +
> down(&misc_sem);
> - c = misc_list.next;
>
> - while ((c != &misc_list) && (c->minor != misc->minor))
> + c = misc_list.next;
> + while (c != &misc_list) {
> + if (c->minor == misc->minor) {
> + up(&misc_sem);
> + return -EBUSY;
> + }
> c = c->next;
> - if (c == &misc_list) {
> - up(&misc_sem);
> - return -EBUSY;
> }
>
> if (misc->minor == MISC_DYNAMIC_MINOR) {

This is fine as well, and possibly more readable.