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

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Message-ID: <20230729150901.25b9ae0c@rorschach.local.home>
Date:   Sat, 29 Jul 2023 15:09:01 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Josh Poimboeuf <jpoimboe@...nel.org>
Cc:     Valentin Schneider <vschneid@...hat.com>,
        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>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
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        Joel Fernandes <joel@...lfernandes.org>,
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Subject: Re: [RFC PATCH v2 02/20] tracing/filters: Enable filtering a
 cpumask field by another cpumask

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++)
		;


-- 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;
> > +  
>