tree 0c1a36c3121eabcc9ff337ad06ff25bc7d78a816
parent c99fc27c6d4a5f48f8f9cef42a7ff9fe40ff0dde
author Josh Poimboeuf <jpoimboe@kernel.org> 1699376192 -0800
committer Josh Poimboeuf <jpoimboe@kernel.org> 1734989465 -0800

perf: Add deferred user callchains

Instead of attempting to unwind user space from the NMI handler, defer
it to run in task context by sending a self-IPI and then scheduling the
unwind to run in the IRQ's exit task work before returning to user space.

This allows the user stack page to be paged in if needed, avoids
duplicate unwinds for kernel-bound workloads, and prepares for SFrame
unwinding (so .sframe sections can be paged in on demand).

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>