Re: [PATCH v1 1/3] coding-style.rst: document BUG() and WARN() rules ("do not crash the kernel")

From: David Hildenbrand
Date: Tue Oct 04 2022 - 08:32:59 EST

On 26.09.22 09:44, Kalle Valo wrote:
David Hildenbrand <david@xxxxxxxxxx> writes:

+Use WARN_ON_ONCE() rather than WARN() or WARN_ON()
+WARN_ON_ONCE() is generally preferred over WARN() or WARN_ON(), because it
+is common for a given warning condition, if it occurs at all, to occur
+multiple times. This can fill up and wrap the kernel log, and can even slow
+the system enough that the excessive logging turns into its own, additional

FWIW I have had cases where WARN() messages caused a reboot, maybe
mention that here? In my case the logging was so excessive that the
watchdog wasn't updated and in the end the device was forcefully

That should be covered by the last part, no? What would be your suggestion?

I was just thinking that maybe make it more obvious that even WARN_ON()
can crash the system, something along these lines:

"..., additional problem like stalling the system so much that it causes
a reboot."

Hi Kalle,

sorry for the late reply. Jonathan already queued v2 and sent it upstream.

I think that's it is already covered by the statement and that the additional example isn't required -- most of us learned the hard way that "excessive logging turns into its own problem" includes all weird kinds of kernel crashes. A panic/reboot due to a watchdog not firing is one such possible outcome.



David / dhildenb