JVM Warning

[George Gastaldi]

Hello,

I am using JDK 1.7.0_40 and when I start XADisk, I get the following message when starting up:

Java HotSpot(TM) 64-Bit Server VM warning: You have loaded library /tmp/xadisk/native/unix_32_xadisk.native which might have disabled stack guard. The VM will try to fix the stack guard now.
It's highly recommended that you fix the library with 'execstack -c <libfile>', or link it with '-z noexecstack'.

Is there any way to fix that? It looks like it should be fixed in the library itself, but I am not sure.

Thanks

[Nitin Verma]

Hi George,

Can you try fixing it with the execstack -c command as suggested in the warning above.

Thanks,
Nitin

[George Gastaldi]

Already did, but it didn't work. The message keeps showing up.

2013/10/11 Nitin Verma <emailt...@gmail.com>

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[Nitin Verma]

You can replace "unix_32_xadisk.native" in the xadiskHome/native directory. Or, you can replace it in the xadisk.jar/rar but make sure to delete the existing lib from xadiskHome/native directory.

[Nitin Verma]

Hi George,

I have created a tracking bug https://java.net/jira/browse/XADISK-149.

Please let me know if you observed any difference with my last update.

Thanks,
Nitin

[George Gastaldi]

Hi Nitin, Thanks for the feedback.

I noticed that for some reason it is trying to load the unix_32_xadisk.native, however I am running on a 64 bit JVM. How do I force the usage of the correct library?

Thanks

[George Gastaldi]

I just ran DurableDiskSession.testNativeLib() and the output was this:

Java HotSpot(TM) 64-Bit Server VM warning: You have loaded library /tmp/xadisk/native/unix_32_xadisk.native which might have disabled stack guard. The VM will try to fix the stack guard now.
It's highly recommended that you fix the library with 'execstack -c <libfile>', or link it with '-z noexecstack'.

Congrats!! The native lib named [unix_64_xadisk] works on your system.

Perhaps a valid fix would be to attempt to load the 64bit libraries first ?

[Nitin Verma]

Hi George,

You may have noticed, the ordering comes from the enum in DurableDiskSession class:

private enum NATIVE_LIB_NAMES {
        unix_32_xadisk, unix_64_xadisk,
        windows_32_xadisk, windows_64_xadisk,
        mac_32_xadisk, mac_64_xadisk,
        placeholder_xadisk
};

To stop the warning message, you can try the workaround of truncating the unix_32 lib to 0 size (just make sure that you delete the already copied libs from the xadiskHome/native directory).

Thanks,
Nitin

[George Gastaldi]

Hi Nitin,

Unfortunately that didn't work. I truncated the file to 0 size and the same message appears. If I delete it, it is replaced by the original version.
I think a simple rearrangement of the enum (64 bit first) could fix the problem. Thoughts?

2013/10/17 Nitin Verma <emailt...@gmail.com>

--

[George Gastaldi]

My suggestion is to change the enum to this:

private enum NATIVE_LIB_NAMES {
        unix_64_xadisk, unix_32_xadisk,
        windows_64_xadisk,windows_32_xadisk,
        mac_64_xadisk, mac_32_xadisk,
        placeholder_xadisk
};

2013/10/17 George Gastaldi <gegas...@gmail.com>

[George Gastaldi]

Hi Nitin,

I downloaded the sources, and applied this change to the enum and the error is gone. Could you change it and test against a 32 bit VM and check if the message is gone too?

Thanks

2013/10/17 George Gastaldi <gegas...@gmail.com>

[Nitin Verma]

Hi George,

During each startup xadisk iterates over this enum and tries to load the binaries in that order and sees which one would work (i implemented this as a workaround to dynamically detecting the platform). For each iteration in this loop, the native lib is copied (from the jar) to the xadiskhome/native directory if it is not present already.

So, you will have to put the truncated lib in the jar and delete all native libs in the xadiskhome/native directory. I hope the error would go with this (because a jvm should not give such kind of warning while loading such blank lib).

Please let me know if it works.

Thanks,
Nitin

[George Gastaldi]

Hi Nitin, 

I cannot tamper the xadisk jar file because it's using the one from the maven repository and people building the project would experience the same warning message. I tested locally and the only solution so far was to change the enum values order as I beforementioned. This will try to load the 64bit lib before the 32bit. I expect no changes for 32bit users because the 64bit version should not load (and should avoid the JVM warning message). The main problem lies in 64bit VMs trying to load a 32bit lib, therefore displaying that annoying message.

--

[Nitin Verma]

Hi George,

Thanks for your inputs. I see the problem with maven build. As you have said, one of the solutions to this JVM warning bug is to alter the orders in enum - 64s before 32s. That would require a basic test on all these platforms (to see if similar warnings don't appear).

You have asked for the 32 bit unix test; unfortunately I cannot that at this moment due to unavailability of setup.

Thanks,
Nitin

[George Gastaldi]

I can assert that this solution works in Fedora 19 64bit with JDK 1.7.0_45 64bits

[gegas...@gmail.com]

Hi Nitin, it's been 2 years now. Can we have this fix included in XADisk? No issues were found after changing the enum order

Thanks

[Nitin Verma]

Hi George,

I can checkin this fix (bug XADISK-149) to svn/trunk, but I am not feeling the next release (with this fix) would come in 1-2 months. Are you looking for a release version with this bug fixed?

Thanks,
Nitin

[gegas...@gmail.com]

Hi Nitin,

Yes, this bug is really annoying and I'd really appreciate if it is fixed asap. I really don't want to consider forking and maintain a separate codebase :)
How about putting the sources in Github? That would make contribution easier.

[Nitin Verma]

Hi George,

I am considering fixing this in some free time next 3-4 days. Will update here once I checkin the changes. The fix is simply what you had updated in https://java.net/jira/browse/XADISK-149.

I didnt have a chance to explore github much. Let me check (I think that would also involve moving away from java.net's repository, and other things probably).

Thanks,
Nitin

[Nitin Verma]

Resolved the jira issue https://java.net/jira/browse/XADISK-149.