[Cluster-devel] "->ls_in_recovery" not released

[Menyhart Zoltan]

> I'd suggest getting it from cluster.git STABLE3 or RHEL6 branches instead.

Could you please indicate the exact URL?


I have got a concern about the robustness of the DLM.

The Linux rules say: one should not return to user mode while holding a lock.
This is because one should not trust the user mode programs whether they
eventually re-enter the kernel or not, in order to release the lock.

For the very same reason (one should not trust the user mode programs),
I think, the DML kernel module is not sufficiently robust.

If you have a closer look, the situation of the "dlm_recoverd" kernel thread
is quite similar to waiting for a user mode program to trigger setting free
a lock.

I can agree: it does not return to user mode.
Yet it holds the lock and goes to sleep, in an um-interruptible way, waiting
for a user action: it trusts 100 % a user mode program, that can be killed,
can bee swapped out and no room to swap it in, etc.

Instead, the DLM should always return in a few seconds, saying the caller
cannot be granted a given "dlm_lock" for a given reason.

E.g. the ocfs2 is able to handle refused lock request. It is up to the
caller to decide if s/he wants to wait more.

I think whatever the user land does, the DLM kernel module should give
a response to a "dlm_lock()" request within a short (for a human operator)
time.


Thanks for your response,

Zoltan Menyhart