From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <49674C62.5090009@domain.hid> Date: Fri, 09 Jan 2009 13:08:50 +0000 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <493306F5.2080605@domain.hid> <49330CD3.4090700@domain.hid> <4933BAE2.3000502@domain.hid> <4933F1A4.8060209@domain.hid> <4933F18F.7080103@domain.hid> <4933FE5A.5060501@domain.hid> <49355B5D.8070802@domain.hid> <49355A59.4050600@domain.hid> <49357C02.1090001@domain.hid> <49358003.1080705@domain.hid> <493BF43B.4080208@domain.hid> <493FA528.3060307@domain.hid> <495CC649.1070203@domain.hid> <495CF842.5000100@domain.hid> In-Reply-To: <495CF842.5000100@domain.hid> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-help] pthread cancelation and scheduling magics List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: rpm@xenomai.org Cc: xenomai-help Philippe Gerum wrote: > Gilles Chanteperdrix wrote: >> Wolfgang Grandegger wrote: >>> Wolfgang Grandegger wrote: >>>> Hi Gilles, >>>> >>>> Gilles Chanteperdrix wrote: >>>>> Wolfgang Grandegger wrote: >>>>>> I'm also puzzled why pthread_setschedparam() does make a mode switch >>>>>> to secondary mode (sometimes). >>>>> That is normal. The glibc caches threads priority value, so we have to >>>>> call __real_pthread_setschedparam to update them. This issue has been >>>>> solved differently on trunk, but unfortunately, we can not backport this >>>>> modification on v2.4.x branch. >>>> To get you right. With v2.4.x it is not possible with the POSIX skin to >>>> change the priority of a real-time thread in the primary mode without >>>> loosing determinism (because it will switch to secondary mode). What >>>> options do I have? >>> I gave Xenomai trunk a try and pthread_setschedparam() does not switch >>> to secondary mode any more on my PowerPC test system. Nice, I just get >>> an Oops in thread_delete from time to time. More on that issue later. >>> For my ARM i.mx31 system, a need a few patches to get the Xenomai src's >>> compiled: >>> >>> Index: include/asm-generic/bits/bind.h >>> =================================================================== >>> --- include/asm-generic/bits/bind.h (revision 4450) >>> +++ include/asm-generic/bits/bind.h (working copy) >>> @@ -72,7 +72,7 @@ >>> err = XENOMAI_SYSCALL1(__xn_sys_current, ¤t); >>> if (err) { >>> fprintf(stderr, "Xenomai: error obtaining handle for current " >>> - "thread: %s\n", strerror(err)); >>> + "thread: %s\n", strerror(-err)); >>> exit(1); >>> } >>> __xeno_set_current(current); >>> Index: include/asm-arm/syscall.h >>> =================================================================== >>> --- include/asm-arm/syscall.h (revision 4450) >>> +++ include/asm-arm/syscall.h (working copy) >>> @@ -228,7 +228,7 @@ >>> volatile unsigned long long *const tscp = __xn_tscinfo.u.fr.tsc; >>> volatile unsigned *const counterp = __xn_tscinfo.u.fr.counter; >>> const unsigned mask = __xn_tscinfo.u.fr.mask; >>> - register unsigned long long after, before; >>> + register unsigned long long result; >>> unsigned counter; >>> >>> __asm__ ("ldmia %1, %M0\n": "=r"(result): "r"(tscp), "m"(*tscp)); >>> >>> >>> When I then start my application or cyclictest I get: >>> >>> -bash-3.2# ./cyclictest -n >>> Xenomai: error obtaining handle for current thread: Operation not permitted >>> >>> As the latency program works fine, it seems to be a problem with the >>> POSIX skin. Any idea what it is? >> What version of gcc are you using ? When trying to get xenomai running >> on an ARM platform, I found out that gcc 4.3.1 and 4.3.2 have a bug on >> ARM which thrashes the parameters passed to some xenomai syscalls. >> > > A common issue happens when pthread_self() is inlined in the syscall arg list. > Early gcc 4.x for powerpc has this problem; never tried with newer releases, but > rather made sure to use a temporary variable to pass this value to the syscall. The issue on arm is a similar issue: the problem comes from the "mode_buf" parameter now passed to pthread_create which clobbers the register r0, normally used to pass the syscall number. I am still trying to figure out if it is a bug in Xenomai's syscall inline assembly, or a bug in gcc or binutils. And even if it is a bug in the toolchain, I am afraid we will have to find a workaround in the syscall inline assmbley anyway. -- Gilles.