On Mon, 14 Feb 2022 22:54:23 +0530
"Naveen N. Rao" [off-list ref] wrote:

For x86, commit 0c0593b45c9b4e ("x86/ftrace: Make function graph use 
ftrace directly") also adds recursion check before the call to 
function_graph_enter() in prepare_ftrace_return(). Do we need that on
powerpc as well?

Yes. The function_graph_enter() does not provide any recursion protection,
so if it were to call something that gets function graph traced, it will
crash the machine.

-- Steve