From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4F0C5C63.40105@domain.hid> Date: Tue, 10 Jan 2012 16:42:27 +0100 From: Philippe Gerum MIME-Version: 1.0 References: <4F0B530A.80905@domain.hid> <4F0C5524.9020501@domain.hid> <4F0C58B7.1080602@domain.hid> <4F0C5C00.3060508@domain.hid> <4F0C5C02.50308@domain.hid> In-Reply-To: <4F0C5C02.50308@domain.hid> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-help] Issue with Auto relax and nested mutexes List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Makarand Pradhan Cc: xenomai@xenomai.org On 01/10/2012 04:40 PM, Philippe Gerum wrote: > On 01/10/2012 04:40 PM, Makarand Pradhan wrote: >> Another point: >> >> "These are fast mutexes, the thread does not have to jump to kernel space >> unless the released mutex was actually contented." >> >> When the first task is started with prio 0, I always see that >> rt_mutex_release is invoked in the kernel. even when there is no >> contention. > > I should have added: "unless there is no contention ... or the caller is > a non-rt thread". This is because we have to jump to kernel space to > track rescnt. > Ok, next try: "unless the mutex was contented ... or the caller is a non-rt thread". >> >> I have an instrumented kernel. The kernel trace is given below. In this >> trace only task1 is running at prio 0. It should be easy to follow: >> >> Jan 10 10:36:59 ruggedcom kernel: lo: rescnt: 0, switched: 0 >> Jan 10 10:36:59 ruggedcom kernel: hi: rescnt: 0, switched: 0 >> Jan 10 10:36:59 ruggedcom kernel: lo: rescnt: 1, switched: 1 >> Jan 10 10:36:59 ruggedcom kernel: hi: rescnt: 2, switched: 0 >> Jan 10 10:36:59 ruggedcom kernel: hi: rescnt: 3, switched: 0 >> Jan 10 10:37:01 ruggedcom kernel: hi: rescnt: 3, switched: 0 >> Jan 10 10:37:01 ruggedcom kernel: __rt_mutex_release >> Jan 10 10:37:01 ruggedcom kernel: RML >> Jan 10 10:37:01 ruggedcom kernel: rt_mutex_release: lockcnt: 1 >> Jan 10 10:37:01 ruggedcom kernel: xnsynch_release_thread: BP: 0 >> Jan 10 10:37:01 ruggedcom kernel: hi: rescnt: 2, switched: 0 >> Jan 10 10:37:01 ruggedcom kernel: __rt_mutex_release >> Jan 10 10:37:01 ruggedcom kernel: RML >> Jan 10 10:37:01 ruggedcom kernel: rt_mutex_release: lockcnt: 1 >> Jan 10 10:37:01 ruggedcom kernel: xnsynch_release_thread: BP: 0 >> Jan 10 10:37:01 ruggedcom kernel: hi: rescnt: 1, switched: 0 >> Jan 10 10:37:01 ruggedcom kernel: __rt_mutex_release >> Jan 10 10:37:01 ruggedcom kernel: RML >> Jan 10 10:37:01 ruggedcom kernel: rt_mutex_release: lockcnt: 1 >> Jan 10 10:37:01 ruggedcom kernel: xnsynch_release_thread: BP: 0 >> Jan 10 10:37:01 ruggedcom kernel: hi: rescnt: 0, switched: 0 >> Jan 10 10:37:01 ruggedcom kernel: lo: rescnt: 1, switched: 1 >> Jan 10 10:37:01 ruggedcom kernel: hi: rescnt: 2, switched: 0 >> Jan 10 10:37:01 ruggedcom kernel: hi: rescnt: 3, switched: 0 >> Jan 10 10:37:03 ruggedcom kernel: hi: rescnt: 3, switched: 0 >> Jan 10 10:37:03 ruggedcom kernel: __rt_mutex_release >> Jan 10 10:37:03 ruggedcom kernel: RML >> Jan 10 10:37:03 ruggedcom kernel: rt_mutex_release: lockcnt: 1 >> Jan 10 10:37:03 ruggedcom kernel: xnsynch_release_thread: BP: 0 >> Jan 10 10:37:03 ruggedcom kernel: hi: rescnt: 2, switched: 0 >> Jan 10 10:37:03 ruggedcom kernel: __rt_mutex_release >> Jan 10 10:37:03 ruggedcom kernel: RML >> Jan 10 10:37:03 ruggedcom kernel: rt_mutex_release: lockcnt: 1 >> Jan 10 10:37:03 ruggedcom kernel: xnsynch_release_thread: BP: 0 >> Jan 10 10:37:03 ruggedcom kernel: hi: rescnt: 1, switched: 0 >> Jan 10 10:37:03 ruggedcom kernel: __rt_mutex_release >> Jan 10 10:37:03 ruggedcom kernel: RML >> Jan 10 10:37:03 ruggedcom kernel: rt_mutex_release: lockcnt: 1 >> Jan 10 10:37:03 ruggedcom kernel: xnsynch_release_thread: BP: 0 >> Jan 10 10:37:03 ruggedcom kernel: hi: rescnt: 0, switched: 0 >> Jan 10 10:37:03 ruggedcom kernel: lo: rescnt: 1, switched: 1 >> Jan 10 10:37:03 ruggedcom kernel: hi: rescnt: 2, switched: 0 >> Jan 10 10:37:03 ruggedcom kernel: hi: rescnt: 3, switched: 0 >> Jan 10 10:37:04 ruggedcom kernel: hi: rescnt: 3, switched: 0 >> >> >> root@domain.hid:~# ./a.out 0 1 >> Spawning: tasks >> bP: 0, cp: 0, mode: 0 >> Acquire complete >> Release complete >> bP: 0, cp: 0, mode: 0 >> Acquire complete >> Release complete >> bP: 0, cp: 0, mode: 0 >> Acquire complete >> ^C >> >> >> Rgds, >> Mak. >> >> >> >> On 10/01/12 10:26 AM, Makarand Pradhan wrote: >>> Hi Phillippe, >>> >>> You are right. Task 1 requires to be started with prio 0. I start seeing >>> the problem after task2 grabs the mutex and releases them. The first >>> task never jumps back to seconodary. Here is my output. The mode never >>> goes back to 0 after "Grabbing mux in HP" and the rescnt stays stuck at >>> 1 in the kernel. >>> >>> root@domain.hid:~# ./relax 0 1 >>> Spawning: tasks >>> bP: 0, cp: 0, mode: 0 >>> Acquire complete >>> Release complete >>> bP: 0, cp: 0, mode: 0 >>> Acquire complete >>> Release complete >>> bP: 0, cp: 0, mode: 0 >>> Acquire complete >>> Release complete >>> bP: 0, cp: 0, mode: 0 >>> Acquire complete >>> Grabbing mux in HP >>> Mux held by Task2 >>> Release complete >>> bP: 0, cp: 0, mode: 1 >>> Acquire complete >>> Release complete >>> bP: 0, cp: 0, mode: 1 >>> Acquire complete >>> >>> Rgds, >>> Mak. >>> >>> >>> On 10/01/12 10:11 AM, Philippe Gerum wrote: >>>> On 01/09/2012 09:50 PM, Makarand Pradhan wrote: >>>>> Hi, >>>>> >>>>> I am running kernel 3.0.0, xenomai: 2.6, powerpc 8360. >>>>> >>>>> I am noticing an issue while using the auto relax feature related to >>>>> mutexes. I am using nested mutexes. The code is attached to this >>>>> email. >>>>> >>>>> The problem is that I am not relaxing after a RT thread grabs and >>>>> releases a mutex. On further investigation, it was noted that the >>>>> rescnt >>>>> is not going down to 0. >>>> From your code, task1 would auto-relax only if started with priority 0, >>>> which is what I get here: >>>> >>>> -bash-3.2# ./relax 0 1 >>>> Spawning: tasks >>>> bP: 0, cp: 0, mode: 0 >>>> Acquire complete >>>> Release complete >>>> bP: 0, cp: 0, mode: 0 >>>> Acquire complete >>>> Release complete >>>> bP: 0, cp: 0, mode: 0 >>>> Acquire complete >>>> Release complete >>>> ... >>>> >>>> Conversely, I get the right behavior if setting a non-zero priority to >>>> task1: >>>> >>>> -bash-3.2# ./relax 1 0 >>>> Spawning: tasks >>>> bP: 1, cp: 1, mode: 1 >>>> Acquire complete >>>> Release complete >>>> bP: 1, cp: 1, mode: 1 >>>> Acquire complete >>>> Release complete >>>> bP: 1, cp: 1, mode: 1 >>>> Acquire complete >>>> ... >>>> >>>> In any case, the priority of task2 should have no impact on the result. >>>> >>>> I'm running current 2.6 HEAD commit (168da46de), kernel 3.1.5/powerpc32 >>>> (52xx), pipeline 2.13-06. >>>> >>>> Which priority arguments are you passing to your test program? >>>> >>>>> Another observation is that I do not hit >>>>> rt_mutex_release in the kernel in the problem scenario, I believe when >>>>> the thread undergoes a priority inversion.This may be a problem as the >>>>> rescnt would not get decremented. Not sure how the mutex is releasing >>>>> wiithout hitting rt_mutex_relase or am I missing anything? >>>>> >>>> These are fast mutexes, the thread does not have to jump to kernel >>>> space >>>> unless the released mutex was actually contented. >>>> >>>>> If I have both the tasks running at priority 0, I stay in the >>>>> secondary >>>>> domain, rt_mutex_release is invoked as expected, the rescnt goes >>>>> down to >>>>> 0 when all the mutexes are released. >>>>> >>>>> Has anyone faced this problem? >>>>> >>>> I'm unsure there is any yet. Auto-relax applies to non -rt Xenomai >>>> threads only (i.e. prio == 0). >>>> >>>>> Rgds, >>>>> Makarand >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> Xenomai-help mailing list >>>>> Xenomai-help@domain.hid >>>>> https://mail.gna.org/listinfo/xenomai-help >>> >> >> > > -- Philippe.