Messages in this thread | | | Date | Thu, 13 Jul 2006 14:43:41 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] Convert idr's internal locking to _irqsave variant |
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On Thu, 13 Jul 2006 14:03:21 -0700 Roland Dreier <rdreier@cisco.com> wrote:
> > I suspect it'll get really ugly. It's a container library which needs to > > allocate memory when items are added, like the radix-tree. Either it needs > > to assume GFP_ATOMIC, which is bad and can easily fail or it does weird > > things like radix_tree_preload(). > > Actually I don't think it has to be too bad. We could tweak the > interface a little bit so that consumers do something like: > > struct idr_layer *layer = NULL; /* opaque */ > > retry: > spin_lock(&my_idr_lock); > ret = idr_get_new(&my_idr, ptr, &id, layer); > spin_unlock(&my_idr_lock); > > if (ret == -EAGAIN) { > layer = idr_alloc_layer(&my_idr, GFP_KERNEL); > if (!IS_ERR(layer)) > goto retry; > } > > in other words make the consumer responsible for passing in new memory > that can be used for a new entry (or freed if other entries have > become free in the meantime). >
Good point, a try-again loop would work. Do we really need the caller to maintain a cache? I suspect something like
drat: if (idr_pre_get(GFP_KERNEL) == ENOMEM) give_up(); spin_lock(); ret = idr_get_new(); spin_unlock(); if (ret == ENOMEM) goto drat;
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