From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <559D189A.8060800@siemens.com> Date: Wed, 08 Jul 2015 14:33:30 +0200 From: Jan Kiszka MIME-Version: 1.0 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> In-Reply-To: <20150708123205.GM20176@hermes.click-hack.org> 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: Gilles Chanteperdrix Cc: Xenomai 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. Jan -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux