include/asm-generic/bug.h: clarify valid uses of WARN()
Explicitly state that WARN*() should be used only for recoverable kernel
issues/bugs and that it should not be used for any kind of invalid
external inputs or transient conditions.
Motivation: it's a very useful capability to be able to understand if a
particular kernel splat means a kernel bug or simply an invalid user-space
program. For the former one wants to notify kernel developers, while
notifying kernel developers for the latter is annoying. Even a kernel
developer may not know what to do with a WARNING in an unfamiliar
subsystem. This is especially critical for any automated testing systems
that may use panic_on_warn and mail kernel developers.
The clear separation also serves as an additional documentation: is it a
condition that must never occur because of additional checks/logic
elsewhere? or is it simply a check for invalid inputs or unfortunate
conditions?
Use of pr_err() for user messages also leads to better error messages.
"Something is wrong in file foo on line X" is not particularly useful
message for end user. pr_err() forces developers to write more meaningful
error messages for user.
As of now we are almost there. We are doing systematic kernel testing
with panic_on_warn and are not seeing massive amounts of false positives.
But every now and then another WARN on ENOMEM or invalid inputs pops up
and leads to a lengthy argument each time. The goal of this change is to
officially document the rules.
Link: http://lkml.kernel.org/r/20180620103716.61636-1-dvyukov@gmail.com
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 file changed