From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751870Ab1JRR4F (ORCPT ); Tue, 18 Oct 2011 13:56:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:20941 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751368Ab1JRR4E (ORCPT ); Tue, 18 Oct 2011 13:56:04 -0400 Date: Tue, 18 Oct 2011 19:55:51 +0200 From: Gleb Natapov To: linux-kernel@vger.kernel.org Cc: Jason Baron , Peter Zijlstra , Steven Rostedt Subject: [PATCH] jump_label_inc may return before the code is patched Message-ID: <20111018175551.GH17571@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If cpu A calls jump_label_inc() just after atomic_add_return() is called by cpu B, atomic_inc_not_zero() will return value greater then zero and jump_label_inc() will return to a caller before jump_label_update() finishes its job on cpu B. Signed-off-by: Gleb Natapov diff --git a/kernel/jump_label.c b/kernel/jump_label.c index a8ce450..e6f1f24 100644 --- a/kernel/jump_label.c +++ b/kernel/jump_label.c @@ -66,8 +66,9 @@ void jump_label_inc(struct jump_label_key *key) return; jump_label_lock(); - if (atomic_add_return(1, &key->enabled) == 1) + if (atomic_read(&key->enabled) == 0) jump_label_update(key, JUMP_LABEL_ENABLE); + atomic_inc(&key->enabled); jump_label_unlock(); } -- Gleb.