From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
The previous ftrace detour implementation fc76b8b8011 ("riscv: Using
PATCHABLE_FUNCTION_ENTRY instead of MCOUNT") contain three problems. The
most horrible bug is preemption panic which found by Andy [1]. I think we
could disable preemption for ftrace first, and Andy could continue the
ftrace preemption work.
@Andy, as Steven said, improving stop_machine mechinism also could prevent
preemption problem, but it would reduce the speed of ftrace_modify. How
do you think about the stop_machine solution, would you give out the
patch for this?
[1]: https://lpc.events/event/16/contributions/1171/
Andy Chiu (1):
riscv: ftrace: Fixup panic by disabling preemption
Guo Ren (2):
riscv: ftrace: Remove wasted nops for !RISCV_ISA_C
riscv: ftrace: Reduce the detour code size to half
arch/riscv/Kconfig | 2 +-
arch/riscv/Makefile | 6 ++-
arch/riscv/include/asm/ftrace.h | 46 ++++++++++++++++++-----
arch/riscv/kernel/ftrace.c | 65 ++++++++++-----------------------
arch/riscv/kernel/mcount-dyn.S | 43 +++++++++-------------
5 files changed, 78 insertions(+), 84 deletions(-)
--
2.36.1
