linux-kernel - Re: [PATCH v2] net: make unregister netdev warning timeout configurable

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Message-ID: <YFsHEwkqCq91ngwn@unreal>
Date:   Wed, 24 Mar 2021 11:32:03 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     davem@...emloft.net, edumazet@...gle.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: make unregister netdev warning timeout
 configurable

On Tue, Mar 23, 2021 at 07:49:23AM +0100, Dmitry Vyukov wrote:
> 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.
> Add net.core.netdev_unregister_timeout_secs sysctl to 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
> 
> ---
> Changes since v1:
>  - use sysctl instead of a config
> ---
>  Documentation/admin-guide/sysctl/net.rst | 11 +++++++++++
>  include/linux/netdevice.h                |  1 +
>  net/core/dev.c                           |  6 +++++-
>  net/core/sysctl_net_core.c               | 10 ++++++++++
>  4 files changed, 27 insertions(+), 1 deletion(-)
> 

Thanks,
Reviewed-by: Leon Romanovsky <leonro@...dia.com>