Eric Dumazet 8e81baeb83 tcp: fix SO_RCVLOWAT related hangs under mem pressure ... [ Upstream commit f969dc5a88 ] While commit 24adbc1676 ("tcp: fix SO_RCVLOWAT hangs with fat skbs") fixed an issue vs too small sk_rcvbuf for given sk_rcvlowat constraint, it missed to address issue caused by memory pressure. 1) If we are under memory pressure and socket receive queue is empty. First incoming packet is allowed to be queued, after commit 76dfa60820 ("tcp: allow one skb to be received per socket under memory pressure") But we do not send EPOLLIN yet, in case tcp_data_ready() sees sk_rcvlowat is bigger than skb length. 2) Then, when next packet comes, it is dropped, and we directly call sk->sk_data_ready(). 3) If application is using poll(), tcp_poll() will then use tcp_stream_is_readable() and decide the socket receive queue is not yet filled, so nothing will happen. Even when sender retransmits packets, phases 2) & 3) repeat and flow is effectively frozen, until memory pressure is off. Fix is to consider tcp_under_memory_pressure() to take care of global memory pressure or memcg pressure. Fixes: 24adbc1676 ("tcp: fix SO_RCVLOWAT hangs with fat skbs") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Arjun Roy <arjunroy@google.com> Suggested-by: Wei Wang <weiwan@google.com> Reviewed-by: Wei Wang <weiwan@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org>		2021-03-04 11:37:33 +01:00
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acpi	ACPICA: Fix exception code class checks	2021-03-04 11:37:24 +01:00
asm-generic	vmlinux.lds.h: Define SANTIZER_DISCARDS with CONFIG_GCOV_KERNEL=y	2021-03-04 11:37:19 +01:00
clocksource
crypto
drm	drm/dp/mst: Export drm_dp_get_vc_payload_bw()	2021-02-10 09:29:18 +01:00
dt-bindings	ASoC: dt-bindings: lpass: Fix and common up lpass dai ids	2021-02-03 23:28:46 +01:00
keys
kunit	kunit: fix display of failed expectations for strings	2020-11-10 13:45:15 -07:00
kvm
linux	bpf: Avoid warning when re-casting __bpf_call_base into __bpf_call_base_args	2021-03-04 11:37:22 +01:00
math-emu
media	media: v4l2-fwnode: v4l2_fwnode_endpoint_parse caller must init vep argument	2020-12-30 11:53:11 +01:00
memory
misc
net	tcp: fix SO_RCVLOWAT related hangs under mem pressure	2021-03-04 11:37:33 +01:00
pcmcia
ras
rdma	RDMA: Lift ibdev_to_node from rds to common code	2021-02-26 10:12:59 +01:00
scsi	scsi: libiscsi: Fix NOP race condition	2020-11-16 22:32:50 -05:00
soc	net: dsa: felix: implement port flushing on .phylink_mac_link_down	2021-02-17 11:02:27 +01:00
sound	ASoC: Fixes for v5.11	2020-11-19 19:56:29 +01:00
target
trace	trace: fix potenial dangerous pointer	2020-11-25 13:03:44 +01:00
uapi	uapi: fix big endian definition of ipv6_rpl_sr_hdr	2021-02-03 23:28:43 +01:00
vdso
video
xen	Xen/gntdev: correct error checking in gntdev_map_grant_pages()	2021-02-23 15:53:24 +01:00