linux-kernel - Re: [PATCH v2 2/4] fprobe: make fprobe_kprobe

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Date:   Tue, 16 May 2023 11:15:48 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ze Gao <zegao2021@...il.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vasily Gorbik <gor@...ux.ibm.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-s390@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        bpf@...r.kernel.org, Conor Dooley <conor@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>, Yonghong Song <yhs@...com>,
        Ze Gao <zegao@...cent.com>
Subject: Re: [PATCH v2 2/4] fprobe: make fprobe_kprobe_handler recursion free

On Tue, May 16, 2023 at 03:18:28PM +0800, Ze Gao wrote:

> +static void fprobe_handler(unsigned long ip, unsigned long parent_ip,
> +		struct ftrace_ops *ops, struct ftrace_regs *fregs)
> +{
> +	struct fprobe *fp;
> +	int bit;
> +
> +	fp = container_of(ops, struct fprobe, ops);
> +	if (fprobe_disabled(fp))
> +		return;
> +
> +	/* recursion detection has to go before any traceable function and
> +	 * all functions before this point should be marked as notrace
> +	 */
> +	bit = ftrace_test_recursion_trylock(ip, parent_ip);
> +	if (bit < 0) {
> +		fp->nmissed++;
> +		return;
> +	}
> +	__fprobe_handler(ip, parent_ip, ops, fregs);
>  	ftrace_test_recursion_unlock(bit);
> +
>  }
>  NOKPROBE_SYMBOL(fprobe_handler);
>  
>  static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip,
>  				  struct ftrace_ops *ops, struct ftrace_regs *fregs)
>  {
> -	struct fprobe *fp = container_of(ops, struct fprobe, ops);
> +	struct fprobe *fp;
> +	int bit;
> +
> +	fp = container_of(ops, struct fprobe, ops);
> +	if (fprobe_disabled(fp))
> +		return;
> +
> +	/* recursion detection has to go before any traceable function and
> +	 * all functions called before this point should be marked as notrace
> +	 */
> +	bit = ftrace_test_recursion_trylock(ip, parent_ip);
> +	if (bit < 0) {
> +		fp->nmissed++;
> +		return;
> +	}

Please don't use this comment style; multi line comments go like:

	/*
	 * Multi line comment ...
	 *                    ... is symmetric.
	 */

Same for your next patch.