netdev - Re: [PATCH net] bridge: start hello_timer when enabling KERNEL_STP in br_stp

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Date:   Fri, 19 May 2017 17:45:38 +0300
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     Xin Long <lucien.xin@...il.com>,
        network dev <netdev@...r.kernel.org>
Cc:     davem@...emloft.net, cera@...a.cz
Subject: Re: [PATCH net] bridge: start hello_timer when enabling KERNEL_STP in
 br_stp_start

On 5/19/17 5:20 PM, Xin Long wrote:
> Since commit 76b91c32dd86 ("bridge: stp: when using userspace stp stop
> kernel hello and hold timers"), bridge would not start hello_timer if
> stp_enabled is not KERNEL_STP when br_dev_open.
> 
> The problem is even if users set stp_enabled with KERNEL_STP later,
> the timer will still not be started. It causes that KERNEL_STP can
> not really work. Users have to re-ifup the bridge to avoid this.
> 
> This patch is to fix it by starting br->hello_timer when enabling
> KERNEL_STP in br_stp_start.
> 
> As an improvement, it's also to start hello_timer again only when
> br->stp_enabled is KERNEL_STP in br_hello_timer_expired, there is
> no reason to start the timer again when it's NO_STP.
> 
> Fixes: 76b91c32dd86 ("bridge: stp: when using userspace stp stop kernel hello and hold timers")
> Reported-by: Haidong Li <haili@...hat.com>
> Signed-off-by: Xin Long <lucien.xin@...il.com>
> ---
>   net/bridge/br_stp_if.c    | 1 +
>   net/bridge/br_stp_timer.c | 2 +-
>   2 files changed, 2 insertions(+), 1 deletion(-)
> 

This doesn't make much sense to me, how do you change from USER_STP to
KERNEL_STP without first going through NO_STP ?

If you go through NO_STP then all will be fine because br_stp_stop will restart
the timers if the previous val was USER_STP.