netdev - Re: [PATCH net] sctp: fix missing wake ups in some situations

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Date:   Fri, 08 Sep 2017 10:07:07 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     marcelo.leitner@...il.com
Cc:     netdev@...r.kernel.org, linux-sctp@...r.kernel.org,
        nhorman@...driver.com, vyasevich@...il.com, laforge@...monks.org
Subject: Re: [PATCH net] sctp: fix missing wake ups in some situations

From: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Date: Fri,  8 Sep 2017 11:35:21 -0300

> Commit fb586f25300f ("sctp: delay calls to sk_data_ready() as much as
> possible") minimized the number of wake ups that are triggered in case
> the association receives a packet with multiple data chunks on it and/or
> when io_events are enabled and then commit 0970f5b36659 ("sctp: signal
> sk_data_ready earlier on data chunks reception") moved the wake up to as
> soon as possible. It thus relies on the state machine running later to
> clean the flag that the event was already generated.
> 
> The issue is that there are 2 call paths that calls
> sctp_ulpq_tail_event() outside of the state machine, causing the flag to
> linger and possibly omitting a needed wake up in the sequence.
> 
> One of the call paths is when enabling SCTP_SENDER_DRY_EVENTS via
> setsockopt(SCTP_EVENTS), as noticed by Harald Welte. The other is when
> partial reliability triggers removal of chunks from the send queue when
> the application calls sendmsg().
> 
> This commit fixes it by not setting the flag in case the socket is not
> owned by the user, as it won't be cleaned later. This works for
> user-initiated calls and also for rx path processing.
> 
> Fixes: fb586f25300f ("sctp: delay calls to sk_data_ready() as much as possible")
> Reported-by: Harald Welte <laforge@...monks.org>
> Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>

Applied and queued up for -stable, th anks.