Re: [PATCH v4 0/2] fix & prevent the missing preemption disabling

[王贇 <yun.wang@linux.alibaba.com>]

Just a ping, to see if there are any more comments :-P

Regards,
Michael Wang

On 2021/10/18 上午11:38, 王贇 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.
> 
> And since the internal using of trace_test_and_set_recursion()
> and trace_clear_recursion() also require preemption to be disabled, we
> can just merge the logical together.
> 
> Patch 1/2 will make sure preemption disabled when recursion lock succeed,
> patch 2/2 will do smp_processor_id() checking after trylock() to address the
> issue.
> 
> v1: https://lore.kernel.org/all/8c7de46d-9869-aa5e-2bb9-5dbc2eda395e@linux.alibaba.com/
> v2: https://lore.kernel.org/all/b1d7fe43-ce84-0ed7-32f7-ea1d12d0b716@linux.alibaba.com/
> v3: https://lore.kernel.org/all/609b565a-ed6e-a1da-f025-166691b5d994@linux.alibaba.com/
> 
> Michael Wang (2):
>   ftrace: disable preemption when recursion locked
>   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      | 20 +++++++++++++++++++-
>  kernel/livepatch/patch.c             | 13 +++++++------
>  kernel/trace/ftrace.c                | 15 +++++----------
>  kernel/trace/trace_event_perf.c      |  6 +++---
>  kernel/trace/trace_functions.c       |  5 -----
>  10 files changed, 34 insertions(+), 35 deletions(-)
>