8000 CPU Percentage: after realloc the pointer becomes invalid; by dothebart · Pull Request #639 · collectd/collectd · GitHub
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CPU Percentage: after realloc the pointer becomes invalid; #639

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Merged
merged 1 commit into from
Jul 24, 2014
Merged

CPU Percentage: after realloc the pointer becomes invalid; #639

merged 1 commit into from
Jul 24, 2014

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dothebart
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need to work on new pointer else we will crash.

fixes https://gist.github.com/toni-moreno/a2f80021535f87202de7

@toni-moreno
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hi @dothebart, thanks a lot by this fix.

It is easy to reproduce the crash in, #587 we need only restarting several times. So I've been building a little testing set which does a big loop restart with different configurations ( adding a plugin on each loop iteration) and counting crashes.

I will test with my current binaries ( compiled on a RHEL 5.5 kernel 2.6.18-194.el5) and after I will patch with this fix.

I will send you the results in a few days.

Thank you very much!

@toni-moreno
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hi @dothebart I'm still working on some kind of test to validate your fix, I agree that it seems a clear bug in the realloc pointer.

The crashed where detected on 69187b7, compiled over RHEL 5.6 on a server exact like a production server.

When I did the loop of 500 restarts adding a plugin on each iteration , the number of crashes with this binaries were:

1.-plugin_graphite.conf:0
2.-plugin_memory.conf:0
3.-plugin_swap.conf:2
4.-plugin_df.conf:3
5.-plugin_disk.conf:2
6.-plugin_processes.conf:1
7.-plugin_interface.conf:1
8.-plugin_cpu.conf:159
9.-plugin_ping.conf:481

As you can see after added the cpu plugin the crashes grow exponentially

After I did the same test changing the plugin order with the following results:

0.-plugin_graphite.conf:0
1.-plugin_cpu.conf:209
2.-plugin_memory.conf:183
3.-plugin_swap.conf :195
4.-plugin_df.conf:610
5.-plugin_disk.conf:192
6.-plugin_processes.conf:415
7.-plugin_interface.conf:158
8.-plugin_ping.conf:204

As you can see again after cpu plugin loads the crash number grow exponentially.

Then I tried to recompile it and I choose the last commit d76d251 ( since no significant changes found) .

But now I can not reproduce it on a testing machine after recompiling with other hardware and compiled over RHEL 5.9.

I'm sure this bug is responsible for most of crashes but I can not reproduce it.

I will try to patch on next days directly on the machines where are still crashing and I will report results to you

Thank you very match!

pyr added a commit that referenced this pull request Jul 24, 2014
@pyr
Merge pull request #639 from dothebart/fix_cpu_crash
fff2e10 
CPU Percentage: after realloc the pointer becomes invalid;
@pyr pyr merged commit fff2e10 into collectd:master Jul 24, 2014
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pyr commented Jul 24, 2014

thanks @dothebart

@pyr
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pyr commented Jul 24, 2014

@toni-moreno thanks for the helpful pointers

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@dothebart @toni-moreno @pyr
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