diff options
| author | Andrii Nakryiko <[email protected]> | 2024-04-18 12:09:08 -0700 |
|---|---|---|
| committer | Masami Hiramatsu (Google) <[email protected]> | 2024-05-01 23:18:48 +0900 |
| commit | b0e28a4b5becea84ae6fca5cbd8a6b80a134e223 (patch) | |
| tree | 436194932eee40c5eced2d6019b6d28287ffaf7a | |
| parent | 0dc715295d4143d1659879f7f50ad4e9a6f6a99c (diff) | |
ftrace: make extra rcu_is_watching() validation check optional
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 validation of ftrace subsystem invariants. For most users it
should probably be kept disabled to eliminate unnecessary runtime
overhead.
This improves BPF multi-kretprobe (relying on ftrace and rethook
infrastructure) runtime throughput by 2%, according to BPF benchmarks ([0]).
[0] https://lore.kernel.org/bpf/CAEf4BzauQ2WKMjZdc9s0rBWa01BYbgwHN6aNDXQSHYia47pQ-w@mail.gmail.com/
Link: https://lore.kernel.org/all/[email protected]/
Cc: Steven Rostedt <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
| -rw-r--r-- | include/linux/trace_recursion.h | 2 | ||||
| -rw-r--r-- | kernel/trace/Kconfig | 13 |
2 files changed, 14 insertions, 1 deletions
diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h index d48cd92d2364..24ea8ac049b4 100644 --- a/include/linux/trace_recursion.h +++ b/include/linux/trace_recursion.h @@ -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(); \ diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index 47345bf1d4a9..d093e16d01c1 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -974,6 +974,19 @@ 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 execution" + 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 is only to verify that + ftrace (and other users of ftrace_test_recursion_trylock()) are not + called outside of RCU, as if they are, it can cause a race. But it + also has a noticeable overhead when enabled. + + If unsure, say N + config RING_BUFFER_RECORD_RECURSION bool "Record functions that recurse in the ring buffer" depends on FTRACE_RECORD_RECURSION |