Re: [Dazuko-devel] 2.0.6 released

[John Ogness]

Calin A. Culianu wrote:
> Is there some known issue that 2.0.6 fixed (esp. with respect to 2.6.11 
> kernels) that was present in 2.0.5?  Could this issue lead to lockups?  
> I am asking since I am not sure if the lockup was more likely due to 
> some idiocy in my app or some actual possible (hard to reproduce) bug in 
> dazuko on Linux?

Hi,

The only changes from 2.0.5 to 2.0.6 have to do with fixes in LSM for the 
Linux 2.6 kernel. This means you. :)

In 2.0.5 there was an ugly typo in the LSM stacking code. I do not quite 
understand how 2.0.5 is able to compile. The possible side-effects of this 
error would be that capabilities might not work correctly. But that is all.

There were no changes from 2.0.5 to 2.0.6 that would fix a lockup. Lockups 
can occur if your registered application blocks on some resource and there 
are no other registered applications in the same group to continue the file 
access control.

It is better to register multiple processes or threads under the same group 
name and let them work together. This can really help if your application 
wants to do blocking-type actions (such a file I/O, network I/O, IPC, etc). 
Remember, if your registered process blocks, then the entire system will 
wait for it to unblock before allowing any further access events. This has 
the effect of a system "lockup".

If your application is only logging/monitoring events and never tries to 
block events, then you should register your application in read-only mode:

dazukoRegister("mygroup", "r");

This reduces the number of kernel/user context switches by 50% and can also 
have some benefits of reducing dead-lock risks.

John Ogness

--
Dazuko Maintainer