netdev - [PATCH] tcp: ensure epoll edge trigger wakeup when out of memory

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Message-Id: <20150515211707.D9FC480066@prod-mail-relay07.akamai.com>
Date:	Fri, 15 May 2015 21:17:07 +0000 (GMT)
From:	Jason Baron <jbaron@...mai.com>
To:	edumazet@...gle.com, davem@...emloft.net
Cc:	netdev@...r.kernel.org, ncardwell@...gle.com, ycheng@...gle.com
Subject: [PATCH] tcp: ensure epoll edge trigger wakeup when out of memory

From: Jason Baron <jbaron@...mai.com>

If we really can't get an skb allocated, make sure that we let
userspace know. This at least gives us a chance to re-try or abort.

Signed-off-by: Jason Baron <jbaron@...mai.com>
---
 net/ipv4/tcp.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index ecccfdc..d7d85e8 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -986,6 +986,9 @@ do_error:
 	if (copied)
 		goto out;
 out_err:
+	/* make sure we wake any epoll edge trigger waiter */
+	if (unlikely(sk->sk_write_queue == 0 && err == -EAGAIN))
+		sk->sk_write_space(sk);
 	return sk_stream_error(sk, flags, err);
 }
 
@@ -1274,6 +1277,9 @@ do_error:
 		goto out;
 out_err:
 	err = sk_stream_error(sk, flags, err);
+	/* make sure we wake any epoll edge trigger waiter */
+	if (unlikely(sk->sk_write_queue == 0 && err == -EAGAIN))
+		sk->sk_write_space(sk);
 	release_sock(sk);
 	return err;
 }
-- 
1.8.2.rc2

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