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Subject: Re: [PATCH v4 0/2] fix & prevent the missing preemption disabling
From:   =?UTF-8?B?546L6LSH?= <yun.wang@linux.alibaba.com>
To:     Guo Ren <guoren@kernel.org>, Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>,
        "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
        Helge Deller <deller@gmx.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Thomas Gleixner <tglx@linutronix.de>,
        Borislav Petkov <bp@alien8.de>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Jiri Kosina <jikos@kernel.org>,
        Miroslav Benes <mbenes@suse.cz>,
        Petr Mladek <pmladek@suse.com>,
        Joe Lawrence <joe.lawrence@redhat.com>,
        Colin Ian King <colin.king@canonical.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Nicholas Piggin <npiggin@gmail.com>,
        Jisheng Zhang <jszhang@kernel.org>, linux-csky@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-parisc@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
        live-patching@vger.kernel.org
References: <32a36348-69ee-6464-390c-3a8d6e9d2b53@linux.alibaba.com>
Message-ID: <71c21f78-9c44-fdb2-f8e2-d8544b3421bd@linux.alibaba.com>
Date:   Tue, 26 Oct 2021 10:09:12 +0800
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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(-)
>