From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753666Ab2KYWd5 (ORCPT ); Sun, 25 Nov 2012 17:33:57 -0500 Received: from mx1.redhat.com ([209.132.183.28]:23814 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753631Ab2KYWdz (ORCPT ); Sun, 25 Nov 2012 17:33:55 -0500 Date: Sun, 25 Nov 2012 23:33:47 +0100 From: Oleg Nesterov To: Ingo Molnar , Peter Zijlstra , Srikar Dronamraju Cc: Ananth N Mavinakayanahalli , Anton Arapov , linux-kernel@vger.kernel.org Subject: [PATCH 2/3] uprobes: Introduce uprobe_is_active() Message-ID: <20121125223347.GA24808@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121125223331.GA24788@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The lifetime of uprobe->rb_node and uprobe->inode is not refcounted, delete_uprobe() is called when we detect that uprobe has no consumers, and it would be deadly wrong to do this twice. Change delete_uprobe() to WARN() if it was already called. We use RB_CLEAR_NODE() to mark uprobe "inactive", then RB_EMPTY_NODE() can be used to detect this case. RB_EMPTY_NODE() is not used directly, we add the trivial helper for the next change. Signed-off-by: Oleg Nesterov --- kernel/events/uprobes.c | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 53dc2eb..2886c82 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -669,6 +669,10 @@ remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vad return set_orig_insn(&uprobe->arch, mm, vaddr); } +static inline bool uprobe_is_active(struct uprobe *uprobe) +{ + return !RB_EMPTY_NODE(&uprobe->rb_node); +} /* * There could be threads that have already hit the breakpoint. They * will recheck the current insn and restart if find_uprobe() fails. @@ -676,9 +680,13 @@ remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vad */ static void delete_uprobe(struct uprobe *uprobe) { + if (WARN_ON(!uprobe_is_active(uprobe))) + return; + spin_lock(&uprobes_treelock); rb_erase(&uprobe->rb_node, &uprobes_tree); spin_unlock(&uprobes_treelock); + RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */ iput(uprobe->inode); put_uprobe(uprobe); } -- 1.5.5.1