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Message-ID: <589412dd594b7efc618728fe68ad6c86f3c60878.camel@perches.com>
Date: Thu, 20 Jul 2023 00:29:42 -0700
From: Joe Perches <joe@...ches.com>
To: paulmck@...nel.org
Cc: rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
kernel-team@...a.com, rostedt@...dmis.org,
Andy Whitcroft <apw@...onical.com>,
Dwaipayan Ray <dwaipayanray1@...il.com>,
Lukas Bulwahn <lukas.bulwahn@...il.com>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
John Fastabend <john.fastabend@...il.com>, bpf@...r.kernel.org
Subject: Re: [PATCH rcu 5/5] checkpatch: Complain about unexpected uses of
RCU Tasks Trace
On Mon, 2023-07-17 at 16:34 -0700, Paul E. McKenney wrote:
> On Mon, Jul 17, 2023 at 03:34:14PM -0700, Joe Perches wrote:
> > On Mon, 2023-07-17 at 11:04 -0700, Paul E. McKenney wrote:
> > > 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.
> > >
> > > Cc: Andy Whitcroft <apw@...onical.com> (maintainer:CHECKPATCH)
> > > Cc: Joe Perches <joe@...ches.com> (maintainer:CHECKPATCH)
> > > Cc: Dwaipayan Ray <dwaipayanray1@...il.com> (reviewer:CHECKPATCH)
> > > Cc: Lukas Bulwahn <lukas.bulwahn@...il.com>
> > > Cc: Alexei Starovoitov <ast@...nel.org>
> > > Cc: Daniel Borkmann <daniel@...earbox.net>
> > > Cc: John Fastabend <john.fastabend@...il.com>
> > > Cc: <bpf@...r.kernel.org>
> > > Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> > > ---
> > > scripts/checkpatch.pl | 18 ++++++++++++++++++
> > > 1 file changed, 18 insertions(+)
> > >
> > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> > []
> > > @@ -7457,6 +7457,24 @@ sub process {
> > > }
> > > }
> > >
> > > +# Complain about RCU Tasks Trace used outside of BPF (and of course, RCU).
> > > + if ($line =~ /\brcu_read_lock_trace\s*\(/ ||
> > > + $line =~ /\brcu_read_lock_trace_held\s*\(/ ||
> > > + $line =~ /\brcu_read_unlock_trace\s*\(/ ||
> > > + $line =~ /\bcall_rcu_tasks_trace\s*\(/ ||
> > > + $line =~ /\bsynchronize_rcu_tasks_trace\s*\(/ ||
> > > + $line =~ /\brcu_barrier_tasks_trace\s*\(/ ||
> > > + $line =~ /\brcu_request_urgent_qs_task\s*\(/) {
> > > + if ($realfile !~ m@...rnel/bpf@ &&
> > > + $realfile !~ m@...clude/linux/bpf@ &&
> > > + $realfile !~ m@...t/bpf@ &&
> > > + $realfile !~ m@...rnel/rcu@ &&
> > > + $realfile !~ m@...clude/linux/rcu@) {
> >
> > Functions and paths like these tend to be accreted.
> >
> > Please use a variable or 2 like:
> >
> > 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/bfp/ |
^^
kernel/bfp/ |
(umm, oops...)
I think my original suggestion works better when I don't typo the path.
> > include/linux/bpf |
> > net/bpf/ |
> > kernel/rcu/ |
> > include/linux/rcu
> > )};
>
> Like this?
>
> # 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 $rcu_trace_paths = qr{(?x:
> kernel/bfp/ |
> include/linux/bpf |
> net/bpf/ |
> kernel/rcu/ |
> include/linux/rcu
> )};
> if ($line =~ /$rcu_trace_funcs/) {
> if ($realfile !~ m@...cu_trace_paths@) {
> WARN("RCU_TASKS_TRACE",
> "use of RCU tasks trace is incorrect outside BPF or core RCU code\n" . $herecurr);
> }
> }
>
> No, that is definitely wrong. It has lost track of the list of pathnames,
> thus complaining about uses of those functions in files where their use
> is permitted.
>
> But this seems to work:
>
> # Complain about RCU Tasks Trace used outside of BPF (and of course, RCU).
> our $rcu_trace_funcs = qr{(?x:
> rcu_read_lock_trace |
> rcu_read_lock_trace_held |
> rcu_read_unlock_trace |
> call_rcu_tasks_trace |
> synchronize_rcu_tasks_trace |
> rcu_barrier_tasks_trace |
> rcu_request_urgent_qs_task
> )};
> if ($line =~ /\b$rcu_trace_funcs\s*\(/) {
> if ($realfile !~ m@...rnel/bpf@ &&
> $realfile !~ m@...clude/linux/bpf@ &&
> $realfile !~ m@...t/bpf@ &&
> $realfile !~ m@...rnel/rcu@ &&
> $realfile !~ m@...clude/linux/rcu@) {
> WARN("RCU_TASKS_TRACE",
> "use of RCU tasks trace is incorrect outside BPF or core RCU code\n" . $herecurr);
> }
> }
>
> Maybe the "^" needs to be distributed into $rcu_trace_paths?
>
> # 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 $rcu_trace_paths = qr{(?x:
> ^kernel/bfp/ |
> ^include/linux/bpf |
> ^net/bpf/ |
> ^kernel/rcu/ |
> ^include/linux/rcu
> )};
> if ($line =~ /\b$rcu_trace_funcs\s*\(/) {
> if ($realfile !~ m@...u_trace_paths@) {
> WARN("RCU_TASKS_TRACE",
> "use of RCU tasks trace is incorrect outside BPF or core RCU code\n" . $herecurr);
> }
> }
>
> But no joy here, either. Which is no surprise, given that perl is
> happy to distribute the "\b" and the "\s*\(" across the elements of
> $rcu_trace_funcs. I tried a number of other variations, including
> inverting the "if" condition "(!(... =~ ...))", inverting the "if"
> condition via an empty "then" clause, replacing the "m@" with "/",
> replacing the "|" in the "qr{}" with "&", and a few others.
>
> Again, listing the pathnames explicitly in the second "if" condition
> works just fine.
>
> Help?
>
> Thanx, Paul
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