[PATCH rcu 5/5] checkpatch: Complain about unexpected uses of RCU Tasks Trace

[Paul E. McKenney]

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@xxxxxxxxxxxxx> (maintainer:CHECKPATCH)
Cc: Joe Perches <joe@xxxxxxxxxxx> (maintainer:CHECKPATCH)
Cc: Dwaipayan Ray <dwaipayanray1@xxxxxxxxx> (reviewer:CHECKPATCH)
Cc: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: John Fastabend <john.fastabend@xxxxxxxxx>
Cc: <bpf@xxxxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
 scripts/checkpatch.pl | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 880fde13d9b8..24bab980bc6f 100755
--- 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@^kernel/bpf@ &&
+			    $realfile !~ m@^include/linux/bpf@ &&
+			    $realfile !~ m@^net/bpf@ &&
+			    $realfile !~ m@^kernel/rcu@ &&
+			    $realfile !~ m@^include/linux/rcu@) {
+				WARN("RCU_TASKS_TRACE",
+				     "use of RCU tasks trace is incorrect outside BPF or core RCU code\n" . $herecurr);
+			}
+		}
+
 # check for lockdep_set_novalidate_class
 		if ($line =~ /^.\s*lockdep_set_novalidate_class\s*\(/ ||
 		    $line =~ /__lockdep_no_validate__\s*\)/ ) {
-- 
2.40.1