@@ -135,7 +135,7 @@ extern void ftrace_record_recursion(unsigned long ip, unsigned long parent_ip);
# define do_ftrace_record_recursion(ip, pip) do { } while (0)
#endif
-#ifdef CONFIG_ARCH_WANTS_NO_INSTR
+#ifdef CONFIG_FTRACE_VALIDATE_RCU_IS_WATCHING
# define trace_warn_on_no_rcu(ip) \
({ \
bool __ret = !rcu_is_watching(); \
@@ -974,6 +974,20 @@ config FTRACE_RECORD_RECURSION_SIZE
This file can be reset, but the limit can not change in
size at runtime.
+config FTRACE_VALIDATE_RCU_IS_WATCHING
+ bool "Validate RCU is on during ftrace recursion check"
+ depends on FUNCTION_TRACER
+ depends on ARCH_WANTS_NO_INSTR
+ help
+ All callbacks that attach to the function tracing have some sort
+ of protection against recursion. This option performs additional
+ checks to make sure RCU is on when ftrace callbacks recurse.
+
+ This is a feature useful for debugging ftrace. This will add more
+ overhead to all ftrace-based invocations.
+
+ If unsure, say N
+
config RING_BUFFER_RECORD_RECURSION
bool "Record functions that recurse in the ring buffer"
depends on FTRACE_RECORD_RECURSION
Introduce CONFIG_FTRACE_VALIDATE_RCU_IS_WATCHING config option to control whether ftrace low-level code performs additional rcu_is_watching()-based validation logic in an attempt to catch noinstr violations. This check is expected to never be true and is mostly useful for low-level debugging of ftrace subsystem. For most users it should probably be kept disabled to eliminate unnecessary runtime overhead. Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> --- include/linux/trace_recursion.h | 2 +- kernel/trace/Kconfig | 14 ++++++++++++++ 2 files changed, 15 insertions(+), 1 deletion(-)