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Date: Fri, 24 Apr 2015 11:07:44 -0400 (EDT) From: David Miller <davem@...emloft.net> To: eric.dumazet@...il.com Cc: johunt@...mai.com, netdev@...r.kernel.org, edumazet@...gle.com, ncardwell@...gle.com, ycheng@...gle.com Subject: Re: [PATCH net] tcp: avoid looping in tcp_send_fin() From: Eric Dumazet <eric.dumazet@...il.com> Date: Thu, 23 Apr 2015 10:42:39 -0700 > From: Eric Dumazet <edumazet@...gle.com> > > Presence of an unbound loop in tcp_send_fin() had always been hard > to explain when analyzing crash dumps involving gigantic dying processes > with millions of sockets. > > Lets try a different strategy : > > In case of memory pressure, try to add the FIN flag to last packet > in write queue, even if packet was already sent. TCP stack will > be able to deliver this FIN after a timeout event. Note that this > FIN being delivered by a retransmit, it also carries a Push flag > given our current implementation. > > By checking sk_under_memory_pressure(), we anticipate that cooking > many FIN packets might deplete tcp memory. > > In the case we could not allocate a packet, even with __GFP_WAIT > allocation, then not sending a FIN seems quite reasonable if it allows > to get rid of this socket, free memory, and not block the process from > eventually doing other useful work. > > Signed-off-by: Eric Dumazet <edumazet@...gle.com> This is really nice, and long overdue, so I'm going to apply this now. Thanks Eric. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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