linux-kernel - Re: [PATCH] soft lockup rose_node_list

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Message-ID: <480CF8AF.9040501@ccr.jussieu.fr>
Date:	Mon, 21 Apr 2008 22:27:27 +0200
From:	Bernard Pidoux <pidoux@....jussieu.fr>
To:	David Miller <davem@...emloft.net>
CC:	ralf@...ux-mips.org, linux-kernel@...r.kernel.org,
	linux-hams@...r.kernel.org,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH] soft lockup rose_node_list_lock

Hi David,

I also spent a lot of time to understand how rose behaved and I agree 
that it is difficult to decifer a code especially dealing
with socket programming and when it was written by someone else.
But as a radioamateur, Linux is a hobby for me and I like to learn.

Actually, rose_get_neigh() is called when two different events are 
occuring :

- first, it is called by rose_connect() in order to find if an adjacent 
node is ready to route to a specific ROSE address.
- second, rose_route_frame() calls rose_get_neigh() every time an 
incoming frame must be routed to an appropriate AX25 connection.

By the way, rose_get_neigh() function is not optimized for it does not 
check if an adjacent node is already connected before a new connect is 
requested.
For this purpose I have derived a new function, I named 
rose_get_route(), that is called by rose_route_frame() to find a route 
via an adjacent node.
This function has been tested for months now and it works fine.
It adds the automatic frames routing that rose needed desperately.
I will send next a patch with this new rose_get_route().

Bernard Pidoux

p.s. my email client is set for MIME attachements, but it seems corrupted.
    I will fix that. Sorry for the unvoluntary increase of workload it 
gave you.


David Miller a écrit :
> From: Bernard Pidoux <pidoux@....jussieu.fr>
> Date: Sun, 20 Apr 2008 19:09:23 +0200
>
>   
>> Since rose_route_frame() does not use rose_node_list we can safely
>> remove rose_node_list_lock spin lock here and let it be free for
>> rose_get_neigh().
>>
>> Signed-off-by: Bernard Pidoux <f6bvp@...at.org>
>>     
>
> Indeed, I went over this code several times and I can't
> see any reason for rose_route_frame() to take the node
> list lock.
>
> Patch applied, thanks Bernard.  But one thing...
>
>   
>> diff --git a/net/rose/rose_route.c b/net/rose/rose_route.c
>> index fb9359f..5053a53 100644
>> --- a/net/rose/rose_route.c
>> +++ b/net/rose/rose_route.c
>> @@ -857,7 +857,6 @@ int rose_route_frame(struct sk_buff *skb, ax25_cb *ax25)
>>          src_addr  = (rose_address *)(skb->data + 9);
>>          dest_addr = (rose_address *)(skb->data + 4);
>>
>> -       spin_lock_bh(&rose_node_list_lock);
>>          spin_lock_bh(&rose_neigh_list_lock);
>>          spin_lock_bh(&rose_route_list_lock);
>>
>>     
>
> Could you please fix your email client so it doesn't corrupt
> patches like this?  I've had to apply all of your patches by
> hand because the tabs have been converted into spaces.  Use
> MIME attachments if you have to.
>
> Thanks again.
> --
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>
>   

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