unwind: Add deferred user space unwinding API
Add unwind_user_deferred() which allows callers to schedule task work to
unwind the user space stack before returning to user space. This solves
several problems for its callers:
- Ensure the unwind happens in task context even if the caller may be
running in interrupt context.
- Only do the unwind once, even if called multiple times either by the
same caller or multiple callers.
- Create a "context cookie" which allows trace post-processing to
correlate kernel unwinds/traces with the user unwind.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
7 files changed
