netdev - Re: [PATCH net] tcp/dccp: do not block bh too long in inet_twdr_twkill

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Message-Id: <20150412.210456.227234180754411318.davem@davemloft.net>
Date:	Sun, 12 Apr 2015 21:04:56 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net] tcp/dccp: do not block bh too long in
 inet_twdr_twkill_work()

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Fri, 10 Apr 2015 04:19:07 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> I have seen inet_twdr_twkill_work() blocking softirq for
> periods up to 1.5 seconds, depending on number of timewait sockets.
> 
> This is an unacceptable source of latency.
> 
> Note that inet_twdr_do_twkill_work() releases death_lock spinlock
> for every tw handled, but does not take care of bh enabling.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

I think it makes sense to use local_softirq_pending() here rather
than flip the lock unconditionally.
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