Re: Strange switching [threadname] to secondary mode after exception #0 in kernel-space at 0x80272444

François Legal devel at thom.fr.eu.org
Wed Sep 30 10:48:39 CEST 2020


I might have found what is causing this problem : CONFIG_CPU_SPECTRE

It was the noticeable difference between my last (4.4.189) kernel release not showing this problem, and the next I tried (4.4.227).
If I modify the Kconfig to disable CPU_SPECTRE, the problem does not show up anymore.

I'll dig a little deeper into that now.

François

Le Mercredi, Septembre 30, 2020 08:42 CEST, François Legal <francois.legal at thom.fr.eu.org> a écrit: 
 
> So I decided to dig a little deeper in this problem, and found out that it is not xenomai3.1 specific.
> I tried with xenomai-3.0.9 and linux 4.4.227 -> same problem.
> I thought it might be a matter of ipipe patch not quite fit to 4.4.227, so I decided to try with latest ipipe-4.4.y-cip from git and xenomai 3.0.9, but the same problem happens.
> 
> François
> 
> Le Vendredi, Septembre 25, 2020 18:11 CEST, François Legal via Xenomai <xenomai at xenomai.org> a écrit: 
>  
> > Sorry to come back so late on that topic.
> > I took some time to write a simple test program, which is attached.
> > 
> > Config is as follows :
> > xenomai-3.1
> > linux-4.4.227
> > 
> > François
> > 
> > Le Vendredi, Août 21, 2020 20:04 CEST, Jan Kiszka <jan.kiszka at siemens.com> a écrit: 
> >  
> > > On 20.08.20 15:46, François Legal via Xenomai wrote:
> > > > Using RTNet with multiple interfaces, xenomai 3.1 with linux 4.4
> > > > Whenever a posix RT thread calls recvmsg (), I get this error.
> > > > 
> > > > I could track this down to line 422 in udp.c :     msg = rtnet_get_arg(fd, &_msg, u_msg, sizeof(_msg));
> > > > 
> > > > If I disassemble the kernel, the failing instruction (at 0x80272444) is a nop in arm_copy_from_user
> > > > Am I doing anything wrong ?
> > > 
> > > Maybe you are passing an invalid pointer to recvmsg, directly or in its
> > > message structures. That would cause an exception which is fixed up but
> > > also reported. Do you get an error in return?
> > > 
> > > Jan
> > > 
> > > -- 
> > > Siemens AG, Corporate Technology, CT RDA IOT SES-DE
> > > Corporate Competence Center Embedded Linux
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