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b2ea46fe23
An overall throughput gain of 22 % for heavy TCP use over a single TX queue. Original patchset comment https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v4.13&id=3f4888adae7c1619b990d98a9b967536f71822b8 Signed-off-by: Pavel Kubelun <be.dissent@gmail.com>
41 lines
1.5 KiB
Diff
41 lines
1.5 KiB
Diff
From 0a9648f1293966c838dc570da73c15a76f4c89d6 Mon Sep 17 00:00:00 2001
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From: Eric Dumazet <edumazet@google.com>
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Date: Wed, 21 Dec 2016 05:42:43 -0800
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Subject: [PATCH 09/10] tcp: add a missing barrier in tcp_tasklet_func()
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Madalin reported crashes happening in tcp_tasklet_func() on powerpc64
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Before TSQ_QUEUED bit is cleared, we must ensure the changes done
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by list_del(&tp->tsq_node); are committed to memory, otherwise
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corruption might happen, as an other cpu could catch TSQ_QUEUED
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clearance too soon.
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We can notice that old kernels were immune to this bug, because
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TSQ_QUEUED was cleared after a bh_lock_sock(sk)/bh_unlock_sock(sk)
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section, but they could have missed a kick to write additional bytes,
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when NIC interrupts for a given flow are spread to multiple cpus.
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Affected TCP flows would need an incoming ACK or RTO timer to add more
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packets to the pipe. So overall situation should be better now.
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Fixes: b223feb9de2a ("tcp: tsq: add shortcut in tcp_tasklet_func()")
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Signed-off-by: Eric Dumazet <edumazet@google.com>
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Reported-by: Madalin Bucur <madalin.bucur@nxp.com>
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Tested-by: Madalin Bucur <madalin.bucur@nxp.com>
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Tested-by: Xing Lei <xing.lei@nxp.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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net/ipv4/tcp_output.c | 1 +
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1 file changed, 1 insertion(+)
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--- a/net/ipv4/tcp_output.c
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+++ b/net/ipv4/tcp_output.c
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@@ -769,6 +769,7 @@ static void tcp_tasklet_func(unsigned lo
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list_del(&tp->tsq_node);
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sk = (struct sock *)tp;
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+ smp_mb__before_atomic();
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clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags);
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if (!sk->sk_lock.owned &&
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