+++ This bug was initially created as a clone of Bug #1189671 +++

From Petr Mladek:

When on it. Would you like to enable?

CONFIG_PRINTK_CALLER=y

It adds extra information about the caller into the console/syslog
output. It might be used to sort mixed lines. It looks like:

[161722.464573] [ T1695] sysrq: Show backtrace of all active CPUs
[161722.471152] [ T1695] NMI backtrace for cpu 1
[161722.471163] [ T1695] CPU: 1 PID: 1695 Comm: bash Not tainted
5.14.0-rc1-default+ #276
[161722.471196] [ T1695] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014
[161722.471201] [ T1695] Call Trace:
[161722.471218] [ T1695]  dump_stack_lvl+0x47/0x60
[161722.471340] [ T1695]  nmi_cpu_backtrace+0xf1/0x110
[161722.471403] [ T1695]  ? lapic_can_unplug_cpu+0xa0/0xa0
[...]
[161722.471793] [ T1695] R13: 0000000000000001 R14: 00007f0d0e9c3720 R15:
0000000000000002
[161722.471864] [ T1695] Sending NMI from CPU 1 to CPUs 0,2-3:
[161722.472021] [    C2] NMI backtrace for cpu 2 skipped: idling at
native_safe_halt+0xb/0x10
[161722.472061] [    C3] NMI backtrace for cpu 3 skipped: idling at
native_safe_halt+0xb/0x10
[161722.472093] [    C0] NMI backtrace for cpu 0 skipped: idling at
native_safe_halt+0xb/0x10

, where "echo l > /proc/sysrq-trigger" was called by the process PID 1695.
The backtrace on this CPU was printed in the same context. While the backtrace
on the other CPUs were printed in IRQ context of the respective CPU.