ftrace_dump_on_oops

Official reference

Determines whether ftrace_dump() should be called on an oops (or kernel panic). This will output the contents of the ftrace buffers to the console. This is very useful for capturing traces that lead to crashes and outputting them to a serial console.

======================= ===========================================
0                       Disabled (default).
1                       Dump buffers of all CPUs.
2(orig_cpu)             Dump the buffer of the CPU that triggered the
                        oops.
<instance>              Dump the specific instance buffer on all CPUs.
<instance>=2(orig_cpu)  Dump the specific instance buffer on the CPU
                        that triggered the oops.
======================= ===========================================

Multiple instance dump is also supported, and instances are separated by commas. If global buffer also needs to be dumped, please specify the dump mode (1/2/orig_cpu) first for global buffer.

So for example to dump “foo” and “bar” instance buffer on all CPUs, user can::

echo “foo,bar” > /proc/sys/kernel/ftrace_dump_on_oops

To dump global buffer and “foo” instance buffer on all CPUs along with the “bar” instance buffer on CPU that triggered the oops, user can::

echo “1,foo,bar=2” > /proc/sys/kernel/ftrace_dump_on_oops