diff options
| author | Eric Dumazet <edumazet@google.com> | 2019-08-16 21:26:22 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-09-06 10:19:45 +0200 |
| commit | fda2092976b38e238b338bf717744faab89c6883 (patch) | |
| tree | bc15bfc0d161170d0a6d55391ddfe7e947806819 /net/core | |
| parent | 53856af73d8577a4017b9762d7406f47df192bed (diff) | |
tcp: make sure EPOLLOUT wont be missed
[ Upstream commit ef8d8ccdc216f797e66cb4a1372f5c4c285ce1e4 ]
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/stream.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/net/core/stream.c b/net/core/stream.c index 1086c8b280a8..6e41b20bf9f8 100644 --- a/net/core/stream.c +++ b/net/core/stream.c @@ -118,7 +118,6 @@ 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(wait); if (sk_stream_memory_free(sk)) @@ -131,11 +130,8 @@ 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); @@ -167,7 +163,13 @@ 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: |