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From: Neal Cardwell <ncardwell@google.com>
To: Eric Dumazet <edumazet@google.com>
Cc: "David S . Miller" <davem@davemloft.net>,
	netdev <netdev@vger.kernel.org>,
	Soheil Hassas Yeganeh <soheil@google.com>,
	Eric Dumazet <eric.dumazet@gmail.com>,
	Jason Baron <jbaron@akamai.com>,
	Vladimir Rutsky <rutsky@google.com>
Subject: Re: [PATCH net] tcp: remove empty skb from write queue in error cases
Date: Mon, 26 Aug 2019 13:18:23 -0400	[thread overview]
Message-ID: <CADVnQynhZ3Vr9pC5_id4z5d3Y-RhVr5c-AapbQcVntZ1=DN9YA@mail.gmail.com> (raw)
In-Reply-To: <20190826161915.81676-1-edumazet@google.com>

On Mon, Aug 26, 2019 at 12:19 PM Eric Dumazet <edumazet@google.com> wrote:
>
> Vladimir Rutsky reported stuck TCP sessions after memory pressure
> events. Edge Trigger epoll() user would never receive an EPOLLOUT
> notification allowing them to retry a sendmsg().
>
> Jason tested the case of sk_stream_alloc_skb() returning NULL,
> but there are other paths that could lead both sendmsg() and sendpage()
> to return -1 (EAGAIN), with an empty skb queued on the write queue.
>
> This patch makes sure we remove this empty skb so that
> Jason code can detect that the queue is empty, and
> call sk->sk_write_space(sk) accordingly.
>
> Fixes: ce5ec440994b ("tcp: ensure epoll edge trigger wakeup when write queue is empty")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Jason Baron <jbaron@akamai.com>
> Reported-by: Vladimir Rutsky <rutsky@google.com>
> Cc: Soheil Hassas Yeganeh <soheil@google.com>
> Cc: Neal Cardwell <ncardwell@google.com>
> ---

Acked-by: Neal Cardwell <ncardwell@google.com>

Nice detective work. :-) Thanks, Eric!

neal

  parent reply	other threads:[~2019-08-26 17:18 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-26 16:19 [PATCH net] tcp: remove empty skb from write queue in error cases Eric Dumazet
2019-08-26 16:50 ` Soheil Hassas Yeganeh
2019-08-26 17:18 ` Neal Cardwell [this message]
2019-08-26 19:56 ` Jason Baron
2019-08-26 20:04   ` Eric Dumazet
2019-08-28  4:38 ` David Miller
2019-09-11 17:36 ` Christoph Paasch
2019-09-11 20:59   ` Eric Dumazet

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