tcp: guarantee forward progress in tcp_sendmsg() (d4011239) · Commits · 戴 / test

Under high rx pressure, it is possible tcp_sendmsg() never has a chance to allocate an skb and loop forever as sk_flush_backlog() would always return true. Fix this by calling sk_flush_backlog() only if one skb had been allocated and filled before last backlog check. Fixes: ("tcp: make tcp_sendmsg() aware of socket backlog") Signed-off-by:

Eric Dumazet <edumazet@google.com> Acked-by:

Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv4/tcp.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -1084,6 +1084,7 @@ int tcp_sendmsg(struct sock sk, struct msghdr msg, size_t size)
		struct sockcm_cookie sockc;
		int flags, err, copied = 0;
		int mss_now = 0, size_goal, copied_syn = 0;
		bool process_backlog = false;
		bool sg;
		long timeo;

		@@ -1167,9 +1168,10 @@ new_segment:
		if (!sk_stream_memory_free(sk))
		goto wait_for_sndbuf;

		if (sk_flush_backlog(sk))
		if (process_backlog && sk_flush_backlog(sk)) {
		process_backlog = false;
		goto restart;

		}
		skb = sk_stream_alloc_skb(sk,
		select_size(sk, sg),
		sk->sk_allocation,
		@@ -1177,6 +1179,7 @@ new_segment:
		if (!skb)
		goto wait_for_memory;

		process_backlog = true;
		/*
		* Check whether we can use HW checksum.
		*/

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