Messages in this thread Patch in this message | | | Date | Tue, 11 Mar 2008 10:35:17 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 1/5] lib: introduce call_once() |
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On Tue, 11 Mar 2008 21:27:30 +0900 "Akinobu Mita" <akinobu.mita@gmail.com> wrote:
> 2008/3/11, Andrew Morton <akpm@linux-foundation.org>: > > On Tue, 11 Mar 2008 15:10:52 +1100 Nick Piggin <nickpiggin@yahoo.com.au> wrote: > > > > > > #define ONCE() \ > > > > ({ \ > > > > static long flag; \ > > > > \ > > > > return !test_and_set_bit(0, flag); \ > > > > }) > > > > > > > > and then callers can do > > > > > > > > if (ONCE()) > > > > do_something(); > > > > > > > > ? > > This cannot be used directly in the conversions of patch 2 - 5. > Because the callers of call_once() in patch 2 - 5 need to wait for the > complition of "init_routine". Some blocking mechanism is needed.
Of course it can be used in those places. Here's the idr.c conversion:
--- a/lib/idr.c~a +++ a/lib/idr.c @@ -585,14 +585,6 @@ static void idr_cache_ctor(struct kmem_c memset(idr_layer, 0, sizeof(struct idr_layer)); } -static int init_id_cache(void) -{ - if (!idr_layer_cache) - idr_layer_cache = kmem_cache_create("idr_layer_cache", - sizeof(struct idr_layer), 0, 0, idr_cache_ctor); - return 0; -} - /** * idr_init - initialize idr handle * @idp: idr handle @@ -602,7 +594,9 @@ static int init_id_cache(void) */ void idr_init(struct idr *idp) { - init_id_cache(); + if (ONCE()) + idr_layer_cache = kmem_cache_create("idr_layer_cache", + sizeof(struct idr_layer), 0, 0, idr_cache_ctor); memset(idp, 0, sizeof(struct idr)); spin_lock_init(&idp->lock); }
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