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Description of problem:
sysrq+t only displays a header, it doesn't show any task tracebacks.
this is connected to an hp rx5670 console via a telnet connection to
the mp. sysrq + s works on this setup.
[bigeverest:root]# cat /proc/sys/kernel/sysrq
[bigeverest:root]# echo 1 > /proc/sys/kernel/sysrq
Commands may be abbreviated. Commands are:
close close current connection
logout forcibly logout remote user and close the connection
display display operating parameters
mode try to enter line or character mode ('mode ?' for more)
open connect to a site
quit exit telnet
send transmit special characters ('send ?' for more)
set set operating parameters ('set ?' for more)
unset unset operating parameters ('unset ?' for more)
status print status information
toggle toggle operating parameters ('toggle ?' for more)
slc set treatment of special characters
z suspend telnet
environ change environment variables ('environ ?' for more)
telnet> send ?
ao Send Telnet Abort output
ayt Send Telnet 'Are You There'
brk Send Telnet Break
ec Send Telnet Erase Character
el Send Telnet Erase Line
escape Send current escape character
ga Send Telnet 'Go Ahead' sequence
ip Send Telnet Interrupt Process
nop Send Telnet 'No operation'
eor Send Telnet 'End of Record'
abort Send Telnet 'Abort Process'
susp Send Telnet 'Suspend Process'
eof Send Telnet End of File Character
synch Perform Telnet 'Synch operation'
getstatus Send request for STATUS
? Display send options
telnet> send brk
SysRq : Emergency Sync
Syncing device 08:14 ... OK
Syncing device 08:12 ... OK
Syncing device 08:13 ... OK
Syncing device 08:21 ... OK
telnet> send brk
SysRq : Show State
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. echo 1 > /proc/sys/kernel/sysrq
2. send a break + t over console
Actual Results: the following is displayed on the console:
SysRq : Show State
Expected Results: tracebacks of tasks on the system are displayed
What is the output of:
# echo /proc/sys/kernel/printk
If I remember correctly, on AS2.1 for IA64, the default values are:
3 4 1 7
The first number is the console log level, and the second number is
the default message level. When kernel printk's are issued without
a specified message level preceding the output string (KERN_INFO,
KERN_WARNING, KERN_ERR, etc.), then the printk function uses the
second number above as the message level. Then, only if the console
log level is greater than the the message level will the messages be
printed to the console.
The "Show State" string will be always be printed because the sysrq.c
handler temporarily bumps the console log level to 7. But then it
sets it back to its original value, and calls the code that prints out
the back traces. Since those printks do not have a KERN_XXX at the
beginning of each string, the level is set to the default message
level. Therefore, if the first number (the console log level) is
less than the default message level of 4, then the messages are not
printed to the console -- but only go to the kernel's message buffer,
and eventually to /var/log/messages.
So if you do this:
# echo 7 4 1 7 > /proc/sys/kernel/printk
then the back trace code will be displayed. (The first number must
be greater than the second, so "5" would work as well as "7" since it
is greater than the default message level of "4")
> What is the output of:
> # echo /proc/sys/kernel/printk
> If I remember correctly, on AS2.1 for IA64, the default values are:
> 3 4 1 7
yes, that is correct.
> So if you do this:
> # echo 7 4 1 7 > /proc/sys/kernel/printk
> then the back trace code will be displayed. (The first number must
> be greater than the second, so "5" would work as well as "7" since
> it is greater than the default message level of "4")
yes, that worked. thank you Dave.