Description of problem:

In tier_start, we  spawn two threads one for promotion and one for demotion. If the thread creation fails we do a join with out having a value for thread variabl. This can lead into a crash or undefined behaviour.

Version-Release number of selected component (if applicable):

mainline

How reproducible:

Mosty

Steps to Reproduce:

1.create a tier volume
2.Attach tier process into gdb
3.using a break point try creating failure for thread creation in tier_start

Actual results:

crash
Expected results:

Should behave normally

Additional info: