parameter panic – the number of seconds the kernel waits before rebooting on a panic

GNU/Linux PARAMETER

root>cat /proc/sys/kernel/panic
0
root>echo 60 > /proc/sys/kernel/panic
root>cat /proc/sys/kernel/panic
60
root>

PARAMETER EXPLANATION

http://en.wikipedia.org/wiki/Kernel_panic

PARAMETER FUNCTION
panic:

The value in this file represents the number of seconds the kernel
waits before rebooting on a panic. When you use the software watchdog,
the recommended setting is 60.

PARAMETER CODE CONNECTION


http://lxr.linux.no/linux+v3.12.5/kernel/panic.c

Linux KERNEL TESTING signaltest

ABOUT Signal(IPC)

Signals are a limited form of inter-process communication (IPC), typically used in Unix, Unix-like, and other POSIX-compliant operating systems. A signal is an asynchronous notification sent to a process or to a specific thread within the same process in order to notify it of an event that occurred. Signals originated in 1970s Bell Labs Unix and have been more recently specified in the POSIX standard.

When a signal is sent, the operating system interrupts the target process' normal flow of execution to deliver the signal. Execution can be interrupted during any non-atomic instruction. If the process has previously registered a signal handler, that routine is executed. Otherwise, the default signal handler is executed.

TYPICAL COMMANDLINE SESSION
[bash]
$sudo ./signaltest –help
signaltest V 0.85
Usage:
signaltest <options>

-b USEC –breaktrace=USEC send break trace command when latency > USEC
-l LOOPS –loops=LOOPS number of loops: default=0(endless)
-p PRIO –prio=PRIO priority of highest prio thread
-q –quiet print only a summary on exit
-t NUM –threads=NUM number of threads: default=2
-m –mlockall lock current and future memory allocations
-v –verbose output values on stdout for statistics
format: n:c:v n=tasknum c=count v=value in us

$sudo ./signaltest -v -t 10 -l 10
0: 0: 0
0: 1: 118
0: 2: 91
0: 3: 83
0: 4: 80
0: 5: 78
0: 6: 78
0: 7: 80
0: 8: 78
0: 9: 79
$

[/bash]
LINK
https://en.wikipedia.org/wiki/Signal_(IPC)
https://www.ibm.com/developerworks/community/blogs/aimsupport/entry/Finding_the_source_of_signals_on_Linux_with_strace_auditd_or_Systemtap?lang=en

Linux KERNEL TESTING cyclictest DETAIL

ABOUT SOFTWARE TESTING

Software testing is an investigation conducted to provide stakeholders with information about the quality of the software product or service under test.[1] Software testing can also provide an objective, independent view of the software to allow the business to appreciate and understand the risks of software implementation. Test techniques include the process of executing a program or application with the intent of finding software bugs (errors or other defects), and verifying that the software product is fit for use.

TYPICAL COMMANDLINE RELATED EXPOSURE
[bash]
$sudo ./cyclictest –smp -p95 -f -b 200
# /dev/cpu_dma_latency set to 0us
INFO: debugfs mountpoint: /sys/kernel/debug/tracing/
could not set ftrace_enabled to 1
Requested tracer ” not available
could not set tracing_max_latency to 0
policy: fifo: loadavg: 0.16 0.24 0.17 1/364 16976

T: 0 (16976) P:95 I:1000 C: 2902 Min: 7 Act: 15 Avg: 20 Max: 169
# Thread Ids: 16976
# Break thread: 16976
# Break value: 246
could not set ftrace_enabled to 0
[/bash]
[bash]
$sudo ./cyclictest –smp -p95 -f -b 100
# /dev/cpu_dma_latency set to 0us
INFO: debugfs mountpoint: /sys/kernel/debug/tracing/
could not set ftrace_enabled to 1
Requested tracer ” not available
could not set tracing_max_latency to 0
policy: fifo: loadavg: 0.27 0.15 0.14 2/361 16999

T: 0 ( 0) P:95 I:1000 C: 0 Min:1000000 Act: 0 Avg: 0 Max: 0
# Thread Ids: 16999
# Break thread: 16999
# Break value: 161
could not set ftrace_enabled to 0
[/bash]
[bash]
$sudo ./cyclictest –smp -p95 -f -b 1000
# /dev/cpu_dma_latency set to 0us
INFO: debugfs mountpoint: /sys/kernel/debug/tracing/
could not set ftrace_enabled to 1
Requested tracer ” not available
could not set tracing_max_latency to 0
policy: fifo: loadavg: 0.17 0.14 0.14 3/361 17002

T: 0 (17002) P:95 I:1000 C: 35587 Min: 7 Act: 32 Avg: 20 Max: 264
^C# Thread Ids: 17002
could not set ftrace_enabled to 0
$

[/bash]
LINKS
https://events.static.linuxfound.org/sites/events/files/slides/cyclictest.pdf
https://en.wikipedia.org/wiki/Software_testing

Advanced Programmable Interrupt Controller

Connected From This

APIC
In   computing,   an   Advanced  Programmable   Interrupt
Controller   (APIC)  is   a  more   complex  Programmable
Interrupt  Controller (PIC)  than Intel's  original types
such  as  the 8259A.  APIC  devices  permit more  complex
priority  models, and  Advanced  IRQ (Interrupt  Request)
management.

In computing,  a programmable interrupt  controller (PIC)
is a  device that is  used to combine several  sources of
interrupt  onto one  or  more CPU  lines, while  allowing
priority   levels  to  be   assigned  to   its  interrupt
outputs. When  the device has  multiple interrupt outputs
to  assert, it  will assert  them in  the order  of their
relative priority

source : http://en.wikipedia.org/wiki/Advanced_Programmable_Interrupt_Controller

Kernel Panic….

Call Trace:  {panic+483}
{_spin_unlock_
irq+12}
       {__down_read+60}
{_spin_lock_irqsave+ 9}
       {__up_read+25}
{blocking_notifier_cal
l_chain+70}
       {do_exit+141} {kernel_math_error+0}
       <ffffffff80270dfc}{do_invalid_op+173}
{:aacraid:aac_intr
_normal+463}
       <fffffff80269ece}{spin_lock_irqsave+9} {printk+82}
       {error_exit+0} {vgacon_cursor+0}
       {:aacraid:aac_intr_normal+473}
{:aacr
aid:aac_intr_normal+473}
       {:aacraid:aac_rx_intr+55}
{handle_IRQ
_event+41}
       {__do_IRQ+154} {do_IRQ+60}
       {ret_from_intr+0} 
(3) astrax:/home/pgperez>
(3) astrax:/home/pgperez> cat error
       {:aacraid:aac_rx_intr+55}
{handle_IRQ_event+41}
       {__do_IRQ+154} {do_IRQ+60}
       {ret_from_intr+0} 

link : https://bugzilla.redhat.com/show_bug.cgi?format=multiple&id=205778