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

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Message-Id: <20210322.122613.1113183432857887657.davem@davemloft.net>
Date:   Mon, 22 Mar 2021 12:26:13 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     dvyukov@...gle.com
Cc:     edumazet@...gle.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: make unregister netdev warning timeout
 configurable

From: Dmitry Vyukov <dvyukov@...gle.com>
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@...gle.com>
> Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=211877
> Cc: netdev@...r.kernel.org
> Cc: linux-kernel@...r.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.

Thanks.