Merge branch 'bpf-lockdep-fixes'

Alexei Starovoitov says:

====================
v1->v2:
- reworded 2nd patch. It's a real dead lock. Not a false positive
- dropped the lockdep fix for up_read_non_owner in bpf_get_stackid

In addition to preempt_disable patch for socket filters
https://patchwork.ozlabs.org/patch/1032437/
First patch fixes lockdep false positive in percpu_freelist
Second patch fixes potential deadlock in bpf_prog_register
Third patch fixes another potential deadlock in stackmap access
from tracing bpf prog and from syscall.
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>