"Alignment trap" errors filling up log

[Brandon Pedersen]

Hi, I am running CoreCDP 2.0.2. I am running a python program and I am noticing messages like this in /var/log/messages:

Nov 30 19:53:39 mtcdp user.warn kernel: Alignment trap: traacerlinkd (15102) PC=0x413efe40 Instr=0xe5893001 Address=0x463faffd FSR 0x813

Nov 30 19:53:39 mtcdp user.warn kernel: Alignment trap: traacerlinkd (15102) PC=0x413efe44 Instr=0xe5890005 Address=0x463fb001 FSR 0x801

Nov 30 19:53:40 mtcdp user.warn kernel: Alignment trap: traacerlinkd (15115) PC=0x413ed6d0 Instr=0xe597e000 Address=0x0082fc72 FSR 0x013

Nov 30 19:53:40 mtcdp user.warn kernel: Alignment trap: traacerlinkd (15115) PC=0x413efe40 Instr=0xe5893001 Address=0x4cbfb455 FSR 0x801

Nov 30 19:53:40 mtcdp user.warn kernel: Alignment trap: traacerlinkd (15115) PC=0x413efe44 Instr=0xe5890005 Address=0x4cbfb459 FSR 0x801

I don’t know what this means or what it is doing. From what I can tell I don’t see any issues with my program. I am constantly sending data over the cell connection and am thinking it is related to that, but I have no idea what to look for. Are these messages bad? How would I fix it?

Thanks for any help,

-Brandon

[Jesse Gilles]

What is “traacerlinkd”? I can’t find any reference to it anywhere.

The log messages means that the kernel detected a mis-aligned memory access by that particular process and it tries to fix it if possible. If the process doesn’t crash then it may not cause any noticeable problems, but it is generally indicative of an alignment bug.

[Brandon Pedersen]

traacerlinkd is my custom python service. The process didn’t crash, I had it running for at least 24 hours (constantly pumping data) and it ran just fine. I am not sure when these messages started showing in the log, I have made several changes to the program, using different libraries…and also switching to 2.0.2 from 1.1.1. I just happened to check the log after all these changes to make sure no under-the-cover errors were happening and saw this. I guess I will need to figure out which library is causing this.

Right now I know I am using 2 modules that have C bindings which I suspect are probably causing this. One is the pybsddb (Berkeley DB) bindings from here http://www.jcea.es/programacion/pybsddb.htm (the built-in version that ships with Python doesn’t work since Berkeley DB on 2.0.2 is 5.x). The other is some Qpid messaging bindings (http://qpid.apache.org) that are generated using Swig.

If I happen to figure out which component is causing these messages, is there anything I can do to fix it? I am comfortable creating patches and everything but I am not too familiar with the low-level C stuff and wouldn’t know what to look for in the code.

I was also looking at a document here http://netwinder.osuosl.org/users/b/brianbr/public_html/alignment.html that says there should be an option that tells the kernel to fix the alignment but not log the message but not sure how to do that, any ideas?

[Jesse Gilles]

If the alignment warnings don’t end up causing any issues, which they may not, you can disable the warning as such:

echo 2 > /proc/cpu/alignment

Here is more info on the setting

http://www.kernel.org/doc/Documentation/arm/mem_alignment

Fixing the alignment issue yourself may or may not be simple, but if you’re not too familiar with C debugging, it will be more difficult. It’s probably easier to report the issue to the project authors. Let me know if you narrow it down.

[Jesse Gilles]

How frequently are you seeing the trap warning? I see the timestamps are close together…how many msgs per second? Also, does it do this the entire time the program is running or just once in a while?

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