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| author |   Eric Dumazet <edumazet@google.com> | 2019-08-16 21:26:22 -0700 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2019-08-19 13:07:43 -0700 |
| commit | ef8d8ccdc216f797e66cb4a1372f5c4c285ce1e4 (patch) | |
| tree | 12820529253fbeddbcf136905071a2e1cdf1e57d /net/core | |
| parent | Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net (diff) | |
| download | linux-dev-ef8d8ccdc216f797e66cb4a1372f5c4c285ce1e4.tar.xz linux-dev-ef8d8ccdc216f797e66cb4a1372f5c4c285ce1e4.zip | |
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')
| -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 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: |