Re: [PATCH v2 0/2] fix & prevent the missing preemption disabling

[Steven Rostedt]

Please start a new thread when sending new versions. v2 should not be a
reply to v1. If you want to reference v1, just add it to the cover
letter with a link tag:

Link: https://lore.kernel.org/all/8c7de46d-9869-aa5e-2bb9-5dbc2eda395e@xxxxxxxxxxxxxxxxx/

-- Steve


On Wed, 13 Oct 2021 11:16:56 +0800
王贇 <yun.wang@xxxxxxxxxxxxxxxxx> wrote:

> The testing show that perf_ftrace_function_call() are using smp_processor_id()
> with preemption enabled, all the checking on CPU could be wrong after preemption.
> 
> As Peter point out, the section between ftrace_test_recursion_trylock/unlock()
> pair require the preemption to be disabled as 'Documentation/trace/ftrace-uses.rst'
> explained, but currently the work is done outside of the helpers.
> 
> Patch 1/2 will make sure preemption disabled after trylock() succeed,
> patch 2/2 will do smp_processor_id() checking after trylock to address the
> issue.
> 
> Michael Wang (2):
>   ftrace: disable preemption between ftrace_test_recursion_trylock/unlock()
>   ftrace: do CPU checking after preemption disabled
> 
>  arch/csky/kernel/probes/ftrace.c     |  2 --
>  arch/parisc/kernel/ftrace.c          |  2 --
>  arch/powerpc/kernel/kprobes-ftrace.c |  2 --
>  arch/riscv/kernel/probes/ftrace.c    |  2 --
>  arch/x86/kernel/kprobes/ftrace.c     |  2 --
>  include/linux/trace_recursion.h      | 22 +++++++++++++++++++++-
>  kernel/livepatch/patch.c             |  6 ------
>  kernel/trace/trace_event_perf.c      |  6 +++---
>  kernel/trace/trace_functions.c       |  5 -----
>  9 files changed, 24 insertions(+), 25 deletions(-)
>