lkml.org 
[lkml]   [2004]   [Oct]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [patch] Real-Time Preemption, -RT-2.6.9-rc4-mm1-U8
From
Date
On Thu, 2004-10-21 at 12:11, Jens Axboe wrote:
> On Thu, Oct 21 2004, Thomas Gleixner wrote:
> > On Thu, 2004-10-21 at 11:53, Jens Axboe wrote:
> > > On Thu, Oct 21 2004, Thomas Gleixner wrote:
> > > > On Thu, 2004-10-21 at 11:12, Rui Nuno Capela wrote:
> > > > > [<e018e139>] queuecommand+0x70/0x7c [usb_storage] (24)
> > > >
> > > > As I already pointed out, this is a problem due to up(sema) in
> > > > queuecommand. That's one of the semaphore abuse points, which needs to
> > > > be fixed.
> > > >
> > > > The problem is that semaphores are hold by Process A and released by
> > > > Process B, which makes Ingo's checks trigger
> > >
> > > That's utter crap, it's perfectly valid use.
> >
> > It's not!
> >
> > >From the code:
> >
> > init_MUTEX_LOCKED(&(us->sema));
> >
> > This is used to wait for command completion and therefor we have the
> > completion API. It was used this way because the ancestor of completion
> > (sleep_on) was racy !
>
> I didn't look at the USB code, I'm just saying that it's perfectly valid
> use of a semaphore the pattern you describe (process A holding it,
> process B releasing it).

Yeah, for a semaphore it is, but not for a mutex.

IMHO, this is not clearly seperated and therefor produces a lot of
confusion.

tglx


-
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 14:07    [W:0.708 / U:0.692 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site