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Subject: Re: [PATCH rcu 5/5] checkpatch: Complain about unexpected uses of
 RCU Tasks Trace
From:   Joe Perches <joe@perches.com>
To:     paulmck@kernel.org
Cc:     rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel-team@meta.com, rostedt@goodmis.org,
        Andy Whitcroft <apw@canonical.com>,
        Dwaipayan Ray <dwaipayanray1@gmail.com>,
        Lukas Bulwahn <lukas.bulwahn@gmail.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        John Fastabend <john.fastabend@gmail.com>, bpf@vger.kernel.org
Date:   Thu, 20 Jul 2023 21:38:51 -0700
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On Thu, 2023-07-20 at 20:56 -0700, Paul E. McKenney wrote:

> 
> > That works much better, thank you!  I will update the patch on my
> > next rebase.
> 
> As shown below.  Is this what you had in mind?
[]
> commit 496aa3821b40459b107f4bbc14ca867daad21fb6
> Author: Paul E. McKenney <paulmck@kernel.org>
> Date:   Thu Jul 6 11:48:07 2023 -0700
> 
>     checkpatch: Complain about unexpected uses of RCU Tasks Trace
>     
>     RCU Tasks Trace is quite specialized, having been created specifically
>     for sleepable BPF programs.  Because it allows general blocking within
>     readers, any new use of RCU Tasks Trace must take current use cases into
>     account.  Therefore, update checkpatch.pl to complain about use of any of
>     the RCU Tasks Trace API members outside of BPF and outside of RCU itself.
[]
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> @@ -7457,6 +7457,30 @@ sub process {
>  			}
>  		}
>  
> +# Complain about RCU Tasks Trace used outside of BPF (and of course, RCU).
> +		our $rcu_trace_funcs = qr{(?x:
> +			rcu_read_lock_trace |
> +			rcu_read_lock_trace_held |
> +			rcu_read_unlock_trace |
> +			call_rcu_tasks_trace |
> +			synchronize_rcu_tasks_trace |
> +			rcu_barrier_tasks_trace |
> +			rcu_request_urgent_qs_task
> +		)};
> +		our $rcu_trace_paths = qr{(?x:
> +			kernel/bpf/ |
> +			include/linux/bpf |
> +			net/bpf/ |
> +			kernel/rcu/ |
> +			include/linux/rcu
> +		)};
> +		if ($line =~ /\b$rcu_trace_funcs\s*\(/) {
> +			if ($realfile !~ m@^$rcu_trace_paths@) {
> +				WARN("RCU_TASKS_TRACE",
> +				     "use of RCU tasks trace is incorrect outside BPF or core RCU code\n" . $herecurr);

Exactly yes.

(though I still suggest a capture group to show the function like below)

		if ($line =~ /\b($rcu_trace_funcs)\s*\(/ &&
		    $realfile !~ m{^$rcu_trace_paths}) {
			WARN("RCU_TASKS_TRACE",
			     "use of RCU task trace '$1' is incorrect outside BPF or core RCU code\n" . $herecurr);
		}