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

[Dmitry Vyukov]

On Mon, Mar 22, 2021 at 8:26 PM David Miller <davem@xxxxxxxxxxxxx> wrote:
>
> From: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Date: Sat, 20 Mar 2021 15:28:51 +0100
>
> > 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@xxxxxxxxxx>
> > Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=211877
> > Cc: netdev@xxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
>
> 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@xxxxxxxxxx/T/#u