linux-kernel - Re: [RFC PATCH v2 02/20] tracing/filters: Enable filtering a cpumask field by another cpumask

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Message-ID: <xhsmh4jlks4yw.mognet@vschneid.remote.csb>
Date:   Mon, 31 Jul 2023 12:19:51 +0100
From:   Valentin Schneider <vschneid@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, kvm@...r.kernel.org, linux-mm@...ck.org,
        bpf@...r.kernel.org, x86@...nel.org, rcu@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
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        Wanpeng Li <wanpengli@...cent.com>,
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        Joel Fernandes <joel@...lfernandes.org>,
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        Tom Lendacky <thomas.lendacky@....com>,
        Dionna Glaze <dionnaglaze@...gle.com>,
        Thomas Weißschuh <linux@...ssschuh.net>,
        Juri Lelli <juri.lelli@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
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        Yair Podemsky <ypodemsk@...hat.com>
Subject: Re: [RFC PATCH v2 02/20] tracing/filters: Enable filtering a
 cpumask field by another cpumask

On 29/07/23 15:09, Steven Rostedt wrote:
> On Wed, 26 Jul 2023 12:41:48 -0700
> Josh Poimboeuf <jpoimboe@...nel.org> wrote:
>
>> On Thu, Jul 20, 2023 at 05:30:38PM +0100, Valentin Schneider wrote:
>> >  int filter_assign_type(const char *type)
>> >  {
>> > -	if (strstr(type, "__data_loc") && strstr(type, "char"))
>> > -		return FILTER_DYN_STRING;
>> > +	if (strstr(type, "__data_loc")) {
>> > +		if (strstr(type, "char"))
>> > +			return FILTER_DYN_STRING;
>> > +		if (strstr(type, "cpumask_t"))
>> > +			return FILTER_CPUMASK;
>> > +		}
>>
>> The closing bracket has the wrong indentation.
>>
>> > +		/* Copy the cpulist between { and } */
>> > +		tmp = kmalloc((i - maskstart) + 1, GFP_KERNEL);
>> > +		strscpy(tmp, str + maskstart, (i - maskstart) + 1);
>>
>> Need to check kmalloc() failure?  And also free tmp?
>
> I came to state the same thing.
>
> Also, when you do an empty for loop:
>
>       for (; str[i] && str[i] != '}'; i++);
>
> Always put the semicolon on the next line, otherwise it is really easy
> to think that the next line is part of the for loop. That is, instead
> of the above, do:
>
>       for (; str[i] && str[i] != '}'; i++)
>               ;
>

Interestingly I don't think I've ever encountered that variant, usually
having an empty line (which this lacks) and the indentation level is enough
to identify these - regardless, I'll change it.

>
> -- Steve
>
>
>>
>> > +
>> > +		pred->mask = kzalloc(cpumask_size(), GFP_KERNEL);
>> > +		if (!pred->mask)
>> > +			goto err_mem;
>> > +
>> > +		/* Now parse it */
>> > +		if (cpulist_parse(tmp, pred->mask)) {
>> > +			parse_error(pe, FILT_ERR_INVALID_CPULIST, pos + i);
>> > +			goto err_free;
>> > +		}
>> > +
>> > +		/* Move along */
>> > +		i++;
>> > +		if (field->filter_type == FILTER_CPUMASK)
>> > +			pred->fn_num = FILTER_PRED_FN_CPUMASK;
>> > +
>>