From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753093AbbJFQp4 (ORCPT ); Tue, 6 Oct 2015 12:45:56 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:57760 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752877AbbJFQpx (ORCPT ); Tue, 6 Oct 2015 12:45:53 -0400 X-IBM-Helo: d03dlp01.boulder.ibm.com X-IBM-MailFrom: paulmck@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 09/13] locking/percpu-rwsem: Make percpu_free_rwsem() after kzalloc() safe Date: Tue, 6 Oct 2015 09:45:30 -0700 Message-Id: <1444149934-16764-9-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 2.5.2 In-Reply-To: <1444149934-16764-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20151006164514.GA15516@linux.vnet.ibm.com> <1444149934-16764-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15100616-0009-0000-0000-00000EA0BC29 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Oleg Nesterov This is the temporary ugly hack which will be reverted later. We only need it to ensure that the next patch will not break "change sb_writers to use percpu_rw_semaphore" patches routed via the VFS tree. The alloc_super()->destroy_super() error path assumes that it is safe to call percpu_free_rwsem() after kzalloc() without percpu_init_rwsem(), so let's not disappoint it. Signed-off-by: Oleg Nesterov Signed-off-by: Paul E. McKenney --- kernel/locking/percpu-rwsem.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c index e2621fbbcbd1..9529a30ec57b 100644 --- a/kernel/locking/percpu-rwsem.c +++ b/kernel/locking/percpu-rwsem.c @@ -26,6 +26,13 @@ EXPORT_SYMBOL_GPL(__percpu_init_rwsem); void percpu_free_rwsem(struct percpu_rw_semaphore *brw) { + /* + * XXX: temporary kludge. The error path in alloc_super() + * assumes that percpu_free_rwsem() is safe after kzalloc(). + */ + if (!brw->fast_read_ctr) + return; + free_percpu(brw->fast_read_ctr); brw->fast_read_ctr = NULL; /* catch use after free bugs */ } -- 2.5.2