On Mon, 02 Nov 2015 09:12:29 -0800
"Shi, Yang" [off-list ref] wrote:

Yes, it is common practice for converting sleepable spin lock to raw 
spin lock in -rt to avoid scheduling in atomic context bug.

Note, in a lot of cases we don't just convert spin_locks to raw because
of atomic context. There's times we need to change the design where the
lock is not taken in atomic context (switching preempt_disable() to a
local_lock() for example).

But bpf is much like ftrace and kprobes where they can be taken almost
anywhere, and the do indeed need to be raw.

-- Steve