[Dnsmasq-discuss] CPU spin in master

[Simon Kelley]

On 01/01/16 11:28, Kevin Darbyshire-Bryant wrote:
> Hi Simon,
> 
> First off, Happy New Year!

.... and to you, and all our readers!

> 
> I compiled master ec0628c4b2a06e1fc21216091bb040d61a43b271 on OpenWrt
> (mips Archer C7 v2 platform  Linux 4.1) a few hours ago and have
> experienced dnsmasq going into a tight cpu loop.  Running strace showed
> no syscalls, so is spinning in dnsmasq somewhere.  Kill -9 seemed to be
> the only way out, and the behaviour would return an indeterminate time
> after restart. Unfortunately I didn't have gdb installed on the router,
> dnsmasq compiled with debug, nor any experience with gdb for that
> matter, so it's a very limited amount of info I can offer.
> 
> I tried turning off dnssec usage in case that avoided the problem, which
> it didn't.  I'm not really sure what provokes the behaviour.  However
> I'd been running efef497b890231ba9232d02e7bfaf8273f044622 for a week
> without incident, and have now backed out to
> d3a8b39c7df2f0debf3b5f274a1c37a9e261f94e as of a few hours ago (avoiding
> the arp caching) so far also without incident.
> 
> So this is a pretty vague report of something lurking in very recent code.#

It's pretty good really. I stared at the ARP-caching code and found a
fault in the linked list code that could introduce a cycle and create
exactly the symptoms you're seeing.


Git HEAD or 2.76test2 should do it. Please could you try it?


And many thanks for testing my new code!



Cheers,

Simon

> 
> Cheers,
> 
> Kevin
> 
>  
> 
> 
> 
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