From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick McHardy Subject: Re: proto_unregister sleeps while atomic Date: Wed, 07 Sep 2005 01:02:01 +0200 Message-ID: <431E1FE9.7030405@trash.net> References: <200509070026.34999.daniele@orlandi.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------000704030201010204060600" Cc: linux-kernel@vger.kernel.org, Kernel Netdev Mailing List , "David S. Miller" Return-path: To: Daniele Orlandi In-Reply-To: <200509070026.34999.daniele@orlandi.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org This is a multi-part message in MIME format. --------------000704030201010204060600 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Daniele Orlandi wrote: > I'm looking at proto_unregister() in linux-2.6.13: > > Il calls kmem_cache_destroy() while holding proto_list_lock: > > void proto_unregister(struct proto *prot) > { > write_lock(&proto_list_lock); > > if (prot->slab != NULL) { > kmem_cache_destroy(prot->slab); > > > However, kmem_cache_destroy() may sleep: > > /* Find the cache in the chain of caches. */ > down(&cache_chain_sem); > ^^^^^^^^^^^^^^^^^^^^^^^ > > Am I seeing it right? You're right, good catch. This patch fixes it by moving the lock down to the list-operation which it is supposed to protect. --------------000704030201010204060600 Content-Type: text/plain; name="x" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="x" [NET]: proto_unregister: fix sleeping while atomic proto_unregister holds a lock while calling kmem_cache_destroy, which can sleep. Noticed by Daniele Orlandi . Signed-off-by: Patrick McHardy --- commit 90fdf8bc78b52d40190766c5496a3d8c24903be8 tree 54048218d981ab263b37e0de09ad52f4bd49a000 parent 591bd554f58b7d363167760a606d2a84696772da author Patrick McHardy Wed, 07 Sep 2005 01:00:00 +0200 committer Patrick McHardy Wed, 07 Sep 2005 01:00:00 +0200 net/core/sock.c | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-) diff --git a/net/core/sock.c b/net/core/sock.c --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1528,8 +1528,6 @@ EXPORT_SYMBOL(proto_register); void proto_unregister(struct proto *prot) { - write_lock(&proto_list_lock); - if (prot->slab != NULL) { kmem_cache_destroy(prot->slab); prot->slab = NULL; @@ -1551,6 +1549,7 @@ void proto_unregister(struct proto *prot prot->twsk_slab = NULL; } + write_lock(&proto_list_lock); list_del(&prot->node); write_unlock(&proto_list_lock); } --------------000704030201010204060600--