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Date:   Mon, 25 Oct 2021 22:42:33 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     =?UTF-8?B?546L6LSH?= <yun.wang@linux.alibaba.com>
Cc:     Guo Ren <guoren@kernel.org>, Ingo Molnar <mingo@redhat.com>,
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        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
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        Paul Walmsley <paul.walmsley@sifive.com>,
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        Thomas Gleixner <tglx@linutronix.de>,
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        Masami Hiramatsu <mhiramat@kernel.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
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        linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
        live-patching@vger.kernel.org
Subject: Re: [PATCH v4 0/2] fix & prevent the missing preemption disabling
Message-ID: <20211025224233.61b8e088@rorschach.local.home>
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        <71c21f78-9c44-fdb2-f8e2-d8544b3421bd@linux.alibaba.com>
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On Tue, 26 Oct 2021 10:09:12 +0800
王贇 <yun.wang@linux.alibaba.com> wrote:

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

I guess you missed what went into mainline (and your name found a bug
in my perl script for importing patches ;-)

  https://lore.kernel.org/all/20211019091344.65629198@gandalf.local.home/

Which means patch 1 needs to change:

> +	/*
> +	 * Disable preemption to fulfill the promise.
> +	 *
> +	 * Don't worry about the bit 0 cases, they indicate
> +	 * the disabling behaviour has already been done by
> +	 * internal call previously.
> +	 */
> +	preempt_disable_notrace();
> +
>  	return bit + 1;
>  }
> 
> +/*
> + * Preemption will be enabled (if it was previously enabled).
> + */
>  static __always_inline void trace_clear_recursion(int bit)
>  {
>  	if (!bit)
>  		return;
> 
> +	if (bit > 0)
> +		preempt_enable_notrace();
> +

Where this wont work anymore.

Need to preempt disable and enable always.

-- Steve


>  	barrier();
>  	bit--;
>  	trace_recursion_clear(bit);
> @@ -209,7 +227,7 @@ static __always_inline void trace_clear_recursion(int bit)
>   * tracing recursed in the same context (normal vs interrupt),
>   *