From: David Miller <davem@davemloft.net>
To: edumazet@google.com
Cc: netdev@vger.kernel.org, soheil@google.com, ncardwell@google.com,
eric.dumazet@gmail.com, jbaron@akamai.com, rutsky@google.com
Subject: Re: [PATCH net] tcp: make sure EPOLLOUT wont be missed
Date: Mon, 19 Aug 2019 13:08:37 -0700 (PDT) [thread overview]
Message-ID: <20190819.130837.1772205052483949360.davem@davemloft.net> (raw)
In-Reply-To: <20190817042622.91497-1-edumazet@google.com>
From: Eric Dumazet <edumazet@google.com>
Date: Fri, 16 Aug 2019 21:26:22 -0700
> As Jason Baron explained in commit 790ba4566c1a ("tcp: set SOCK_NOSPACE
> under memory pressure"), it is crucial we properly set SOCK_NOSPACE
> when needed.
>
> However, Jason patch had a bug, because the 'nonblocking' status
> as far as sk_stream_wait_memory() is concerned is governed
> by MSG_DONTWAIT flag passed at sendmsg() time :
>
> long timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
>
> So it is very possible that tcp sendmsg() calls sk_stream_wait_memory(),
> and that sk_stream_wait_memory() returns -EAGAIN with SOCK_NOSPACE
> cleared, if sk->sk_sndtimeo has been set to a small (but not zero)
> value.
>
> This patch removes the 'noblock' variable since we must always
> set SOCK_NOSPACE if -EAGAIN is returned.
>
> It also renames the do_nonblock label since we might reach this
> code path even if we were in blocking mode.
>
> Fixes: 790ba4566c1a ("tcp: set SOCK_NOSPACE under memory pressure")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Jason Baron <jbaron@akamai.com>
> Reported-by: Vladimir Rutsky <rutsky@google.com>
Applied and queued up for -stable.
prev parent reply other threads:[~2019-08-19 20:08 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-17 4:26 [PATCH net] tcp: make sure EPOLLOUT wont be missed Eric Dumazet
2019-08-17 12:39 ` Soheil Hassas Yeganeh
2019-08-17 14:19 ` Jason Baron
2019-08-17 16:26 ` Eric Dumazet
2019-08-19 18:40 ` Jason Baron
2019-08-17 17:10 ` Neal Cardwell
2019-08-19 20:08 ` David Miller [this message]
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