Re: [PATCH] net: make unregister netdev warning timeout configurable

On Mon, Mar 22, 2021 at 8:26 PM David Miller [off-list ref] wrote:

From: Dmitry Vyukov <dvyukov@google.com>
Date: Sat, 20 Mar 2021 15:28:51 +0100

quoted

netdev_wait_allrefs() issues a warning if refcount does not drop to 0
after 10 seconds. While 10 second wait generally should not happen
under normal workload in normal environment, it seems to fire falsely
very often during fuzzing and/or in qemu emulation (~10x slower).
At least it's not possible to understand if it's really a false
positive or not. Automated testing generally bumps all timeouts
to very high values to avoid flake failures.
Make the timeout configurable for automated testing systems.
Lowering the timeout may also be useful for e.g. manual bisection.
The default value matches the current behavior.

Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=211877
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

I'd say a sysctl knob is much better than a compile time setting for this.
That way stock kernels can be used in these testing scenerios.

FTR, I've mailed v2 with a sysctl:
https://lore.kernel.org/netdev/20210323064923.2098711-1-dvyukov@google.com/T/#u (local)