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From: Joachim Fenkes <fenkes@de.ibm.com>
To: linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org,
       jim.houston@ccur.com
Subject: DEFINE_IDR() and the layer cache
Date: Wed, 11 Jul 2007 20:27:29 +0200
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Cc: Christoph Raisch <raisch@de.ibm.com>,
       "Hoang-Nam Nguyen" <hnguyen@de.ibm.com>,
       Stefan Roscher <stefan.roscher@de.ibm.com>
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Hi all,

while the idr discussion is still hot, there's another thing that caught my
eye recently:

As to my reading of idr.h, I have two choices of initializing a global idr:
 a) static struct idr foo; /* ... */ idr_init(&foo);
 b) static DEFINE_IDR(foo);

idr_init(), when called for the first time, sets up the layer
cache. idr_get_new() and friends expect the cache to exist. Now, what happens
if the first call to idr_get_new() targets an idr initialized using
DEFINE_IDR() before idr_init() has been called at least once? Could this
happen?

My $0.02,
  Joachim