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From: Andrew Morton <akpm@linux-foundation.org>
To: "Akinobu Mita" <akinobu.mita@gmail.com>
Cc: nickpiggin@yahoo.com.au, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/5] lib: introduce call_once()
Date: Tue, 11 Mar 2008 10:35:17 -0700	[thread overview]
Message-ID: <20080311103517.5b6dc23f.akpm@linux-foundation.org> (raw)
In-Reply-To: <961aa3350803110527g4d6654ew34847807e46da315@mail.gmail.com>

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);
 }



  reply	other threads:[~2008-03-11 17:35 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-10 14:57 Akinobu Mita
2008-03-10 15:00 ` [PATCH 2/5] idr: use call_once() Akinobu Mita
2008-03-10 15:01   ` [PATCH 3/5] hugetlbfs: " Akinobu Mita
2008-03-10 15:03     ` [PATCH 4/5] shmem: " Akinobu Mita
2008-03-10 15:05       ` [PATCH 5/5] tiny-shmem: " Akinobu Mita
2008-03-10 22:15       ` [PATCH 4/5] shmem: " Hugh Dickins
2008-03-11 12:29         ` Akinobu Mita
2008-03-11 13:41           ` Hugh Dickins
2008-03-10 15:29 ` [PATCH 1/5] lib: introduce call_once() Joe Perches
2008-03-11 12:17   ` Akinobu Mita
2008-03-11  3:48 ` Andrew Morton
2008-03-11  4:10   ` Nick Piggin
2008-03-11  4:21     ` Andrew Morton
2008-03-11 12:27       ` Akinobu Mita
2008-03-11 17:35         ` Andrew Morton [this message]
2008-03-11 18:56           ` Joe Perches
2008-03-11 19:11             ` Andrew Morton
2008-03-15  4:01           ` Akinobu Mita
2008-03-11 12:41 ` Nick Piggin

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