netdev - Re: [PATCH net 1/6] sctp: remove the unnecessary state check in sctp_outq

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Date:   Fri, 9 Sep 2016 01:34:05 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     Neil Horman <nhorman@...driver.com>
Cc:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org,
        davem <davem@...emloft.net>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Vlad Yasevich <vyasevich@...il.com>, daniel@...earbox.net
Subject: Re: [PATCH net 1/6] sctp: remove the unnecessary state check in sctp_outq_tail

>> Data Chunks are only sent by sctp_primitive_SEND, in which sctp checks
>> the asoc's state through statetable before calling sctp_outq_tail. So
>> there's no need to do it again in sctp_outq_tail.
>>
>> This patch is to remove it from sctp_outq_tail.
>>
>> Signed-off-by: Xin Long <lucien.xin@...il.com>
> This doesn't seem safe to me.  The send operation is handled in side effect
> processing off a queue that might have operations queued ahead of it, which
> affect the associations state.  I think you need to keep this check in place
>
But not really for Data Chunk.

There are 3 places calling sctp_outq_tail.
1. in sctp_assoc_rwnd_increase():
   it's for sending sack chunk, so this patch is safe for here
2. sctp_cmd_interpreter(), SCTP_CMD_REPLY:
   still not Data Chunk, so safe.
3.SCTP_CMD_SEND_MSG: ->  sctp_cmd_send_msg()
   it's for Data Chunk, but it's only called by sctp_sf_do_prm_send().

#define TYPE_SCTP_PRIMITIVE_SEND  { \
...
/* SCTP_STATE_COOKIE_WAIT */ \
TYPE_SCTP_FUNC(sctp_sf_do_prm_send), \
/* SCTP_STATE_COOKIE_ECHOED */ \
TYPE_SCTP_FUNC(sctp_sf_do_prm_send), \
/* SCTP_STATE_ESTABLISHED */ \
TYPE_SCTP_FUNC(sctp_sf_do_prm_send), \
/* SCTP_STATE_SHUTDOWN_PENDING */ \


in sctp_sf_do_prm_send():
   sctp_add_cmd_sf(commands, SCTP_CMD_SEND_MSG, SCTP_DATAMSG(msg));
   return SCTP_DISPOSITION_CONSUME;

This function is called by PRIMITIVE_SEND, and every time after
calling sctp_do_sm(), there must be no operations inside.
so it's impossible that other operations queued ahead of it.

I'm not sure if I miss some special case, pls correct me if I'm wrong.

Thanks.