On Tue, Apr 24, 2001 at 02:07:47PM +0100, David Howells wrote:
> It was my implementation that triggered it (I haven't tried it with yours),
> but the bug occurred because the SUBL happened to make the change outside of
> the spinlocked region in the slowpath at the same time as the wakeup routine
> so you reproduced a deadlock with my patch applied, or you are saying
> you discovered that case with one of you testcases?
It was my implementation that triggered it (I haven't tried it with yours),
but the bug occurred because the SUBL happened to make the change outside of
the spinlocked reg
On Tue, Apr 24, 2001 at 02:19:28PM +0200, Andrea Arcangeli wrote:
> I'm starting the benchmarks of the C version and I will post a number update
> and a new patch in a few minutes.
(sorry for the below wrap around, just grow your terminal to read it stright)
aa RW
There is a bug in both the C version and asm version of my rwsem
and it is the slow path where I forgotten to drop the _irq part
from the spinlock calls ;) Silly bug. (I inherit it also in the
asm fast path version because I started hacking the same C slow path)
I catched it now because it locks
On Tue, Apr 24, 2001 at 11:33:13AM +0100, David Howells wrote:
> *grin* Fun ain't it... Try it on a dual athlon or P4 and the answer may come
> out differently.
compile with -mathlon and the compiler then should generate (%%eax) if that's
faster even if the sem is a constant, that's a compiler is
On Tue, Apr 24, 2001 at 11:25:23AM +0100, David Howells wrote:
> > I'd love to hear this sequence. Certainly regression testing never generated
> > this sequence yet but yes that doesn't mean anything. Note that your slow
> > path is very different than mine.
>
> One of my testcases fell over on
> I see what you meant here and no, I'm not lucky, I thought about that. gcc x
> 2.95.* seems smart enough to produce (%%eax) that you hardcoded when the
> sem is not a constant (I'm not clobbering another register, if it does it's
> stupid and I consider this a compiler mistake).
It is a compil
> I'd love to hear this sequence. Certainly regression testing never generated
> this sequence yet but yes that doesn't mean anything. Note that your slow
> path is very different than mine.
One of my testcases fell over on it...
> I don't feel the need of any xchg to enforce additional serializ
On Tue, Apr 24, 2001 at 09:56:11AM +0100, David Howells wrote:
> | +: "+m" (sem->count), "+a" (sem)
^^ I think you were comenting on
the +m not +a ok
>
> >From what I've been told,
> Ok I finished now my asm optimized rwsemaphores and I improved a little my
> spinlock based one but without touching the icache usage.
And I can break it. There's a very good reason the I changed __up_write() to
use CMPXCHG instead of SUBL. I found a sequence of operations that locked up
on thi
On Mon, Apr 23, 2001 at 11:34:35PM +0200, Andrea Arcangeli wrote:
> On Mon, Apr 23, 2001 at 09:35:34PM +0100, D . W . Howells wrote:
> > This patch (made against linux-2.4.4-pre6) makes a number of changes to the
> > rwsem implementation:
> >
> > (1) Everything in try #2
> >
> > plus
> >
> >
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