From mboxrd@z Thu Jan 1 00:00:00 1970 References: <558579E2.9070507@web.de> <559B9B77.3020409@xenomai.org> <559BCBDB.7080208@xenomai.org> <559CFBE7.3050802@siemens.com> <559D0FEC.8030606@xenomai.org> <559D1689.2020102@siemens.com> <20150708123205.GM20176@hermes.click-hack.org> <559D189A.8060800@siemens.com> From: Philippe Gerum Message-ID: <559D1B05.9010503@xenomai.org> Date: Wed, 8 Jul 2015 14:43:49 +0200 MIME-Version: 1.0 In-Reply-To: <559D189A.8060800@siemens.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai] Mayday issues again List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka , Gilles Chanteperdrix Cc: Xenomai On 07/08/2015 02:33 PM, Jan Kiszka wrote: > On 2015-07-08 14:32, Gilles Chanteperdrix wrote: >> On Wed, Jul 08, 2015 at 02:24:41PM +0200, Jan Kiszka wrote: >>> On 2015-07-08 13:56, Philippe Gerum wrote: >>>> On 07/08/2015 12:31 PM, Jan Kiszka wrote: >>>>> On 2015-07-07 14:53, Philippe Gerum wrote: >>>>>> On 07/07/2015 11:27 AM, Philippe Gerum wrote: >>>>>>> I tested the patch on ARM. Enabling IPIPE_DEBUG_INTERNAL there reveals a >>>>>>> bug with the mayday handler now turning hw IRQs on, as a result of >>>>>>> relaxing over the low level IRQ trampoline, which makes some I-pipe call >>>>>>> in the irq_handler boilerplate code unhappy. The very same issue is >>>>>>> looming on x86, with an unprotected call to __ipipe_root_p from >>>>>>> __ipipe_handle_irq(). Disabling IRQs before leaving the mayday handler >>>>>>> is required at the very least. >>>>>>> >>>>>> >>>>>> Looking further, ARM is affected because it does not invoke >>>>>> __ipipe_call_mayday() for triggering the mayday trap, but still uses the >>>>>> open-coded method. This routine preserves the current hw state across >>>>>> the trap, which should make x86 safe in the end. >>>>> >>>>> Which kernel version are you testing? It's not reproducing on 3.14 for >>>>> Cortex-A7/15 targets at least. And I find __ipipe_call_mayday in both >>>>> 3.14 and 3.18 (fastcall_exit_check). >>>>> >>>> >>>> Looking at the code, any kernel version since 3.10 will have the same >>>> issue, older ones likely too, tested on 3.18.12. This does not depend on >>>> the ARM target. >>>> >>>> irq_handler from entry-armv.S: >>>> => __ipipe_grab_irq (or indirecty via ipipe_handle_multi_irq with >>>> MULTI_IRQ enabled) >>>> => __ipipe_exit_irq (open coded __ipipe_notify_trap(MAYDAY), >>>> xnthread_relax() re-enables hw IRQs) >>>> => __ipipe_check_root_interruptible (from irq_handler) >>>> BAD: __ipipe_root_p tested with CPU migration enabled >>>> >>> >>> Maybe [1] makes the difference here? I think I had to fix this for a >>> different reason. >> >> Except this does not work over legacy kernel thread stacks.. > > Xenomai 2 is out of scope for these changes on mayday and for gdb > improvements. > Testing CONFIG_IPIPE_LEGACY for such change would be required then. -- Philippe.