strange SysRq problem

strange SysRq problem

[Hans-Peter Jansen]

Hi,

I'm suffering from a strange SysRq problem:

syslog shows haphazardly "SysRq : HELP" lines, while I definitely didn't 
triggered them, neither via (PS/2) keyboard, nor via /proc/sysrq-trigger.
This is accompanied with stalls of about 15-60 secs. 

Here's an example:

Feb 14 00:16:11 xrated kernel: SysRq : HELP : loglevel0-8 reBoot Crashdump 
tErm Full kIll saK showMem Nice powerOff showPc show-all-timers(Q) unRaw 
Sync showTasks Unmount shoW-blocked-tasks 
Feb 14 00:32:45 xrated kernel: SysRq : HELP : loglevel0-8 reBoot Crashdump 
tErm Full kIll saK showMem Nice powerOff showPc show-all-timers(Q) unRaw 
Sync showTasks Unmount shoW-blocked-tasks 
Feb 14 00:32:57 xrated kernel: SysRq : HELP : loglevel0-8 reBoot Crashdump 
tErm Full kIll saK showMem Nice powerOff showPc show-all-timers(Q) unRaw 
Sync showTasks Unmount shoW-blocked-tasks 
Feb 14 00:32:57 xrated kernel: SysRq : HELP : loglevel0-8 reBoot Crashdump 
tErm Full kIll saK showMem Nice powerOff showPc show-all-timers(Q) unRaw 
Sync showTasks Unmount shoW-blocked-tasks 
Feb 14 00:33:04 xrated kernel: SysRq : HELP : loglevel0-8 reBoot Crashdump 
tErm Full kIll saK showMem Nice powerOff showPc show-all-timers(Q) unRaw 
Sync showTasks Unmount shoW-blocked-tasks 
Feb 14 00:33:24 xrated kernel: SysRq : HELP : loglevel0-8 reBoot Crashdump 
tErm Full kIll saK showMem Nice powerOff showPc show-all-timers(Q) unRaw 
Sync showTasks Unmount shoW-blocked-tasks 
Feb 14 00:33:24 xrated kernel: SysRq : HELP : loglevel0-8 reBoot Crashdump 
tErm Full kIll saK showMem Nice powerOff showPc show-all-timers(Q) unRaw 
Sync showTasks Unmount shoW-blocked-tasks 
Feb 14 00:33:24 xrated kernel: SysRq : HELP : loglevel0-8 reBoot Crashdump 
tErm Full kIll saK showMem Nice powerOff showPc show-all-timers(Q) unRaw 
Sync showTasks Unmount shoW-blocked-tasks 
Feb 14 00:33:24 xrated kernel: SysRq : HELP : loglevel0-8 reBoot Crashdump 
tErm Full kIll saK showMem Nice powerOff showPc show-all-timers(Q) unRaw 
Sync showTasks Unmount shoW-blocked-tasks 
Feb 14 00:33:33 xrated kernel: SysRq : HELP : loglevel0-8 reBoot Crashdump 
tErm Full kIll saK showMem Nice powerOff showPc show-all-timers(Q) unRaw 
Sync showTasks Unmount shoW-blocked-tasks 

Anybody suffered from similar behavior out there, and tracked it down?

TIA,
Pete

Re: strange SysRq problem

[Arnd Hannemann]

Hans-Peter Jansen wrote:
> I'm suffering from a strange SysRq problem:
> 
> syslog shows haphazardly "SysRq : HELP" lines, while I definitely didn't 
> triggered them, neither via (PS/2) keyboard, nor via /proc/sysrq-trigger.
> This is accompanied with stalls of about 15-60 secs. 

Any chance that a device connected via serial (or an USB device which uses USB/Serial conversion)
triggers them? My cheap pl2303 device seems to send spurious BREAKs every once in a while, which
results in the described behavior, as the kernel will print the help line for any character which
is not a valid sysrq. (The probability to trigger another sysrq with random data is much lower, but
did you find any other printout of an sysrq in your logs?)

Best regards,
Arnd Hannemann

Re: strange SysRq problem

[Hans-Peter Jansen]

Am Donnerstag, 14. Februar 2008 schrieb Arnd Hannemann:
> Hans-Peter Jansen wrote:
> > I'm suffering from a strange SysRq problem:
> >
> > syslog shows haphazardly "SysRq : HELP" lines, while I definitely
> > didn't triggered them, neither via (PS/2) keyboard, nor via
> > /proc/sysrq-trigger. This is accompanied with stalls of about 15-60
> > secs.
>
> Any chance that a device connected via serial (or an USB device which
> uses USB/Serial conversion) triggers them? My cheap pl2303 device seems
> to send spurious BREAKs every once in a while, which results in the
> described behavior, as the kernel will print the help line for any
> character which is not a valid sysrq. (The probability to trigger another
> sysrq with random data is much lower, but did you find any other printout
> of an sysrq in your logs?)

Hmm, keyboard (Cherry G80-3000 LPCDE-2) and mouse (Logitech RX300) are 
connected via an equip KVM 2 port switch, but everything else is behaving 
properly, and no serial devices connected ATM. It only triggers the help 
messages, other sysrq messages are triggered at will (AFAIKS).

# grep "SysRq : HELP" /var/log/messages | wc -l
814

syslog starts at Jan 16, so you can imagine how disturbing this behavior is.

I cannot outrule some hardware defects. Will start to eliminate the KVM 
switch, but I thought, I ask here before since google also didn't revealed 
any hints..

Thanks,
Pete