From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4C062106.50809@domain.hid> Date: Wed, 02 Jun 2010 11:14:46 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <20100601135005.GA5483@domain.hid> <1275402757.27918.151.camel@domain.hid> <20100601155403.GA8240@domain.hid> <4C053C51.4090903@domain.hid> <4C061823.70005@domain.hid> In-Reply-To: <4C061823.70005@domain.hid> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-help] Handling Linux Signals in primary domain context List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gilles Chanteperdrix Cc: "xenomai@xenomai.org" Gilles Chanteperdrix wrote: > Jan Kiszka wrote: >> Tschaeche IT-Services wrote: >>> On Tue, Jun 01, 2010 at 04:32:37PM +0200, Philippe Gerum wrote: >>>> Not in the absence of syscall. We thought about this once already, when >>>> considering how a watchdog preempting a runaway task in primary mode >>>> could force a secondary mode switch: there is no sane and easy solution >>>> to this unfortunately. >>> This is exactly Sigmatek's problem: Our customers develop code >>> within our debugging/development environment. We want to catch >>> this situation (the developer implements a while(1)) with a >>> watchdog throwing SIGTRAP so that our debugger gets active >>> and can locate the problem according to the stack frame... >> CONFIG_XENO_OPT_WATCHDOG is probably what you are looking for. It tries >> to catch "well-behaving" broken threads via SIGDEBUG and kills the >> hopelessly broken rest - system alive again. >> >> You can then debug the former and need to do code review on the latter. >> Or you could also try to add some loop-breaking Xenomai syscalls (or >> even more clever checks) to library services the code under suspect >> usually invokes. > > I am afraid "well-behaving" means emitting syscalls. We have a radical > way to cause a SIGSEGV to be sent to a thread having run amok: set its > PC to an invalid address (after having printed the real PC). gdb will > not be able to print where the program stopped, but should be able to > print the backtrace. Just discussing this with our customer raised spontaneous interest (due to the yet unsolved switching issue with non-RT Xenomai threads). I'm going to look into this, also trying to find some more sophisticated approaches, e.g. simulating a call to preserve the call trace (which would make it really useful) or jumping to some helper function that issues a syscall. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux