Re: Jumptable losing reference to samplers

From: Neil McKee <>
Date: 02/08/10
Message-Id: <>

Thanks Andy,

Below is a diff showing the fix. Let me know if this is the same as the fix that you have made.


[root@chow InMon_Agent]# svn diff
Index: sflow_sampler.C
--- sflow_sampler.C (revision 1929)
+++ sflow_sampler.C (working copy)
@@ -25,15 +25,18 @@
      (Thanks to Jagjit Choudray of Force 10 Networks for pointing out this bug) */
   SFLDataSource_instance dsi = *pdsi;
- /* preserve the *nxt pointer too, in case we are resetting this poller and it is
- already part of the agent's linked list (thanks to Matt Woodly for pointing this out) */
+ /* preserve the *nxt pointers too, in case we are resetting this sampler and it is
+ already part of the agent's linked list (thanks to Matt Woodly for pointing this out,
+ and to Andy Kitchingman for pointing out that it applies to the hash_nxt ptr too) */
   SFLSampler *nxtPtr = sampler->nxt;
+ SFLSampler *hashPtr = sampler->hash_nxt;
   /* clear everything */
   memset(sampler, 0, sizeof(*sampler));
- /* restore the linked list ptr */
+ /* restore the linked list and hash-table ptrs */
   sampler->nxt = nxtPtr;
+ sampler->hash_nxt = hashPtr;
   /* now copy in the parameters */
   sampler->agent = agent;

On Feb 8, 2010, at 3:20 PM, andy kitchingman wrote:

> In addition to the fix for Matt Woodley's post "Potential memory leak in sFlow
> API" on 10/05/09, I think the "hash_nxt" pointer to the sampler also needs to
> be preserved when resetting the sampler.
> If a sampler which is stored at a jumptable index (head of list for that slot)
> gets reset, it currently loses the reference to the remaining sampler list
> members that share that hash table slot.
> Regards
> Andy
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Neil McKee
InMon Corp.
Received on Mon Feb 8 15:39:11 2010

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