On Fri, Feb 5, 2010 at 12:08 PM, Simon Wilkinson <[email protected]> wrote: > > On 5 Feb 2010, at 14:23, Rainer Toebbicke wrote: > >> aklog -setpag does not work as expected under Openafs 1.4.11, under RHEL 5. > > Basically, we've not supported changing the PAG of your parent on Linux for a > while now. There's no easy way of fiddling with the group membership of the > parent process without breaking loads of locking assumptions, or using things > that we aren't allowed to have access to. Hence the warning in the manpage. > That said, we haven't consciously set out to break it either, so if this is > something that works in 1.4.x, but not in 1.4.11, and is unrelated to a > kernel version change, I'd be interested to hear more about it. > > In 1.4.x, PAG membership is still determined by a processes group list (in > 1.5.x, we use the keyring as the only source of PAG information) - so the > existence or not of a keyring shouldn't be a problem. However, it does occur > to me that we are now using keyrings for PAG garbage collection - as walking > the process table ceased being an option. It's possible that what's happening > is that we are, through some fluke, succeeding in changing the parent's group > ID. However, we can't (on kernels of RHEL5 vintage) set the keyring of the > parent safely. So only the child has a keyring containing that PAG. When the > child dies, the keyring's reference count hits 0, and so it is garbage > collected. This triggers garbage collection of the associated tokens, and so > the parent loses out. > > I can't think of any easy way to solve this, though, beyond reiterating > "-setpag isn't supported on Linux". Ideas are welcome. > > Cheers, > > Simon.
I'd point out that in very recent kernels (2.6.32+), there is a new system call that allows a process to copy its session keyring to its parent, and in the 1.5 branch there's a commit that uses this to make aklog -setpag work again. I don't believe that it has been pulled up to the 1.4 branch. So on the development branch at least, aklog -setpag should work as expected for current and future kernels. Marc _______________________________________________ OpenAFS-info mailing list [email protected] https://lists.openafs.org/mailman/listinfo/openafs-info
