On Tue, Sep 12, 2000 at 11:37:46AM +0100, Alan Cox wrote:
> That code example can in theory deadlock without any patches if the CPU's
> end up locked in sync with each other and the same one always wins the test.
> It isnt likely on current x86 but other processors are a different story
If seen
On Tue, 12 Sep 2000, Alan Cox wrote:
>That code example can in theory deadlock without any patches if the CPU's
Woops I really meant:
while (test_and_set_bit(0, &lock));
/* critical section */
mb();
clear_bit(0, &lock);
Andrea
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> > while (test_and_set_bit(0, &something)) {
> > /* critical section */
> > mb();
> > clear_bit(0, &something);
> > }
>
> > The above construct it's discouraged of course when you can do
> > the same thing with a spinlock but some place is doing that.
Rik van Riel wrote:
>
> On Tue, 12 Sep 2000, Andrea Arcangeli wrote:
> > On Wed, 6 Sep 2000, George Anzinger wrote:
> >
> > >The times a kernel is not preemptable under this patch are:
> > >
> > >While handling interrupts.
> > >While doing "bottom half" processing.
> > >While holding a spinlock,
On Mon, 11 Sep 2000, Rik van Riel wrote:
>Hmmm, maybe the Montavista people can volunteer to clean
>up all those places in the kernel code? ;)
That would be nice and welcome indipendently of the preemptible kernel
indeed. The right construct to convert that stuff is
spin_is_locked/spin_trylock (
On Tue, 12 Sep 2000, Andrea Arcangeli wrote:
> On Wed, 6 Sep 2000, George Anzinger wrote:
>
> >The times a kernel is not preemptable under this patch are:
> >
> >While handling interrupts.
> >While doing "bottom half" processing.
> >While holding a spinlock, writelock or readlock.
> >
> >At all o
On Wed, 6 Sep 2000, George Anzinger wrote:
>The times a kernel is not preemptable under this patch are:
>
>While handling interrupts.
>While doing "bottom half" processing.
>While holding a spinlock, writelock or readlock.
>
>At all other times the algorithm allows preemption.
So it can deadlock
George Anzinger wrote:
>
> This patch, for 2.4.0-test6, allows the kernel to be built with full
> preemption.
Neat. Congratulations.
> ...
> The measured context switch latencies with this patch
> have been as high as 12 ms, however, we are actively working to
> isolate and fix the areas of t
This patch, for 2.4.0-test6, allows the kernel to be built with full
preemption. The patch relies on the spinlock mechanism to protect areas
of code that should not be preempted. The patch, by way of a small
change to schedule(), allows preemption during times when current->state
is not TASK_RU
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