From mboxrd@z Thu Jan 1 00:00:00 1970 From: Darren Hart Subject: [PATCH 2/4] rtmutex: add BUG_ON if a task attempts to block on two locks Date: Fri, 9 Jul 2010 15:32:58 -0700 Message-ID: <1278714780-788-3-git-send-email-dvhltc@us.ibm.com> References: <1278714780-788-1-git-send-email-dvhltc@us.ibm.com> Cc: Thomas Gleixner , Peter Zijlstra , Ingo Molnar , Eric Dumazet , John Kacur , Steven Rostedt , Mike Galbraith , linux-rt-users@vger.kernel.org, Darren Hart To: linux-kernel@vger.kernel.org Return-path: In-Reply-To: <1278714780-788-1-git-send-email-dvhltc@us.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org rtmutex proxy locking complicates the logic a bit and opens up the possibility for a task to wake and attempt to take another sleeping lock without knowing it has been enqueued on another lock already. Add a BUG_ON to catch this scenario early. Signed-off-by: Darren Hart Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Eric Dumazet Cc: John Kacur Cc: Steven Rostedt Cc: Mike Galbraith --- kernel/rtmutex.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c index baac7d9..22f9d18 100644 --- a/kernel/rtmutex.c +++ b/kernel/rtmutex.c @@ -459,6 +459,9 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock, top_waiter = rt_mutex_top_waiter(lock); plist_add(&waiter->list_entry, &lock->wait_list); + /* Tasks can only block on one lock at a time. */ + BUG_ON(task->pi_blocked_on != NULL); + task->pi_blocked_on = waiter; raw_spin_unlock(&task->pi_lock); -- 1.7.0.4