Messages in this thread | | | Date | Mon, 14 Sep 2015 11:50:08 +0200 | From | Ingo Molnar <> | Subject | Re: [RFC][PATCH RT 0/3] RT: Fix trylock deadlock without msleep() hack |
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* Thomas Gleixner <tglx@linutronix.de> wrote:
> > And if we are into getting reference counts, why not solve it at a higher > > level and get a reference count to 'x' to make sure it's safe to use? Then we > > could do: > > > > lock(y->lock); > > retry: > > x = y->x; > > if (!trylock(x->lock)) { > > get_ref(x->count) > > unlock(y->lock); > > lock(x->lock); > > lock(y->lock); > > put_ref(x->count); > > if (y->x != x) { /* Retry if 'x' got dropped meanwhile */ > > unlock(x->lock); > > goto retry; > > } > > } > > > > Or so. > > In the case of dcache::dentry_kill() we probably do not have to take refcounts > and it might be actually counterproductive to do so. y->x, i.e. dentry->parent, > cannot vanish under us, if I understand the life time rules correctly.
Ok, that's even better.
> Aside of that, yes, I was thinking about a similar scheme for that. I need some > more time to grok all the rules there :)
Ok, great! :-)
I really don't think we need a new locking primitive - and with something like the above we could improve the code upstream as well and make it scale better in some scenarios, right?
Thanks,
Ingo
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