Messages in this thread | | | Date | Sat, 26 Apr 2014 17:35:37 +0100 | From | Al Viro <> | Subject | Re: [PATCH] drm: make variable named "refcount" atomic, like most refcounts in the kernel. |
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On Sat, Apr 26, 2014 at 06:06:15PM +0200, Lionel Debroux wrote: > Based on PaX.
Lovely - cargo-cult at its finest. "Most refcounts are atomic, must be good medicine. Shaman has spoken".
> - int refcount; > + atomic_t refcount;
... therefore, all places that modify that sucker will have to be visible in the patch. And those are
> - ++item->refcount; > + atomic_inc(&item->refcount); > ref->object = item->object; > mutex_unlock(&item->mutex);
and
> mutex_lock(&item->mutex); > - BUG_ON(item->refcount == 0); > + BUG_ON(atomic_read(&item->refcount) == 0); > BUG_ON(ref->object != item->object); > - if (--item->refcount == 0) { > + if (atomic_dec_and_test(&item->refcount)) { > ref->release(ref); > item->object = NULL;
Mind explaining how could we manage to reach either without item->mutex being held, serializing the modifications?
NAK, in case it's not obvious from the above...
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