printk: introduce dump_stack_lvl()

printk: introduce dump_stack_lvl()

dump_stack() is used for many different cases, which may require a log
level consistent with other kernel messages surrounding the dump_stack()
call.  Without that, certain systems that are configured to ignore the
default level messages will miss stack traces in critical error reports.

This patch introduces dump_stack_lvl() that behaves similarly to
dump_stack(), but accepts a custom log level.  The old dump_stack()
becomes equal to dump_stack_lvl(KERN_DEFAULT).

A somewhat similar patch has been proposed in 2012:
https://lore.kernel.org/lkml/1332493269.2359.9.camel@hebo/ , but wasn't
merged.

[[email protected]: add missing dump_stack_lvl() stub if CONFIG_PRINTK=n]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Alexander Potapenko <[email protected]>
Reviewed-by: Marco Elver <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: he, bo <[email protected]>
Cc: Yanmin Zhang <[email protected]>
Cc: Prasad Sodagudi <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>