linux-kernel - RE: [RFC PATCH] net/tipc: reduce tipc_node lock holding time in tipc

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Date:   Fri, 24 Nov 2023 10:22:28 +0000
From:   Tung Quang Nguyen <tung.q.nguyen@...tech.com.au>
To:     xu <xu.xin.sc@...il.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "jmaloy@...hat.com" <jmaloy@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "tipc-discussion@...ts.sourceforge.net" 
        <tipc-discussion@...ts.sourceforge.net>,
        "xu.xin16@....com.cn" <xu.xin16@....com.cn>,
        "yang.yang29@....com.cn" <yang.yang29@....com.cn>,
        "ying.xue@...driver.com" <ying.xue@...driver.com>,
        "zhang.yunkai@....com.cn" <zhang.yunkai@....com.cn>
Subject: RE: [RFC PATCH] net/tipc: reduce tipc_node lock holding time in
 tipc_rcv

>Why can't use le->lock instead of node's lock to protect it in tipc_link_rcv.
>
I have already explained:
__tipc_node_link_down()
{
    ...
   if (!l || tipc_link_is_reset(l)) <-- read link status
    ...
}
>>What I showed you were just 2 use cases (link reset/delete). There are more use cases (netlink, transmit path etc) that need proper
>locks.
>
>The same. We can also add spin_lock_bh(&le->lock) to protect the link in other places where it changes the link status in addition to
>'reset/delete'. Because using node lock to protect the link in tipc_link_rcv is really wasting CPU performance.
>
If you want to change current lock policy, you need to submit a complete/correct patch. I will acknowledge this patch if I can see a significant improvement in my test.