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

From: 王贇
Date: Mon Oct 25 2021 - 22:11:18 EST


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@xxxxxxxxxxxxxxxxx/
> v2: https://lore.kernel.org/all/b1d7fe43-ce84-0ed7-32f7-ea1d12d0b716@xxxxxxxxxxxxxxxxx/
> v3: https://lore.kernel.org/all/609b565a-ed6e-a1da-f025-166691b5d994@xxxxxxxxxxxxxxxxx/
>
> 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(-)
>