On Mon, Mar 09, 2020 at 03:49:53PM +0100, Daniel Glöckner wrote:
> Hello Sascha,
>
> Am 03/06/20 um 20:33 schrieb Sascha Hauer:
> > +static void __slice_acquire(struct slice *slice, int add)
> > +{
> > + struct slice_entry *se;
> > +
> > + slice->acquired += add;
> > +
> > + if (slice->acquired < 0) {
> > + pr_err("Slice %s acquired count drops below zero\n",
> > + slice_name(slice));
> > + dump_stack();
> > + slice->acquired = 0;
> > + return;
> > + }
> > +
> > + list_for_each_entry(se, &slice->deps, list)
> > + __slice_acquire(se->slice, add);
>
> I don't think we need that loop. slice_acquired will already recurse into
> the dependency tree. That loop would also mark resources as used which
> are still unused. The network packet handlers can safely do MDIO transfers
> because the network stack does not talk to the PHY while checking for
> received packets.
Agreed.
>
> > +bool slice_acquired(struct slice *slice)
> > +{
> > + struct slice_entry *se;
> > +
> > + if (slice->acquired)
> > + return true;
> > +
> > + list_for_each_entry(se, &slice->deps, list)
> > + if (slice_acquired(se->slice))
> > + return true;
> > +
> > + return false;
> > +}
>
> It would be nice if this function was able to detect cyclic dependencies
> if DEBUG. This can be done by setting slice->acquired to INT_MIN while
> recursing and checking if any of the values found are negative.
Yes, good idea.
I'll send an update for this.
Sascha
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