Xin Long 4de506d511 sctp: use sk_wmem_queued to check for writable space
[ Upstream commit cd305c74b0 ]

sk->sk_wmem_queued is used to count the size of chunks in out queue
while sk->sk_wmem_alloc is for counting the size of chunks has been
sent. sctp is increasing both of them before enqueuing the chunks,
and using sk->sk_wmem_alloc to check for writable space.

However, sk_wmem_alloc is also increased by 1 for the skb allocked
for sending in sctp_packet_transmit() but it will not wake up the
waiters when sk_wmem_alloc is decreased in this skb's destructor.

If msg size is equal to sk_sndbuf and sendmsg is waiting for sndbuf,
the check 'msg_len <= sctp_wspace(asoc)' in sctp_wait_for_sndbuf()
will keep waiting if there's a skb allocked in sctp_packet_transmit,
and later even if this skb got freed, the waiting thread will never
get waked up.

This issue has been there since very beginning, so we change to use
sk->sk_wmem_queued to check for writable space as sk_wmem_queued is
not increased for the skb allocked for sending, also as TCP does.

SOCK_SNDBUF_LOCK check is also removed here as it's for tx buf auto
tuning which I will add in another patch.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2019-12-01 09:16:39 +01:00
2019-11-24 08:21:09 +01:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
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In order to build the documentation, use ``make htmldocs`` or
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    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
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See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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