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authorEric Dumazet <edumazet@google.com>2019-08-17 07:26:22 +0300
committerDavid S. Miller <davem@davemloft.net>2019-08-19 23:07:43 +0300
commitef8d8ccdc216f797e66cb4a1372f5c4c285ce1e4 (patch)
tree12820529253fbeddbcf136905071a2e1cdf1e57d /net/core/stream.c
parent06821504fd47a5e5b641aeeb638a0ae10a216ef8 (diff)
downloadlinux-ef8d8ccdc216f797e66cb4a1372f5c4c285ce1e4.tar.xz
tcp: make sure EPOLLOUT wont be missed
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> Acked-by: Soheil Hassas Yeganeh <soheil@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Acked-by: Jason Baron <jbaron@akamai.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core/stream.c')
-rw-r--r--net/core/stream.c16
1 files changed, 9 insertions, 7 deletions
diff --git a/net/core/stream.c b/net/core/stream.c
index e94bb02a5629..4f1d4aa5fb38 100644
--- a/net/core/stream.c
+++ b/net/core/stream.c
@@ -120,7 +120,6 @@ int sk_stream_wait_memory(struct sock *sk, long *timeo_p)
int err = 0;
long vm_wait = 0;
long current_timeo = *timeo_p;
- bool noblock = (*timeo_p ? false : true);
DEFINE_WAIT_FUNC(wait, woken_wake_function);
if (sk_stream_memory_free(sk))
@@ -133,11 +132,8 @@ int sk_stream_wait_memory(struct sock *sk, long *timeo_p)
if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN))
goto do_error;
- if (!*timeo_p) {
- if (noblock)
- set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
- goto do_nonblock;
- }
+ if (!*timeo_p)
+ goto do_eagain;
if (signal_pending(current))
goto do_interrupted;
sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
@@ -169,7 +165,13 @@ out:
do_error:
err = -EPIPE;
goto out;
-do_nonblock:
+do_eagain:
+ /* Make sure that whenever EAGAIN is returned, EPOLLOUT event can
+ * be generated later.
+ * When TCP receives ACK packets that make room, tcp_check_space()
+ * only calls tcp_new_space() if SOCK_NOSPACE is set.
+ */
+ set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
err = -EAGAIN;
goto out;
do_interrupted: