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checkpatch: Undeprecate rcu_read_lock_trace() and rcu_read_unlock_trace()

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It turns out that there are BPF use cases that rely on nesting RCU
Tasks Trace readers.  These use cases are well-served by the old
rcu_read_lock_trace() and rcu_read_unlock_trace() functions that maintain
a nesting counter in the task_struct structure.  But these use cases incur
a performance penalty when using the shiny new rcu_read_lock_tasks_trace()
and rcu_read_unlock_tasks_trace() functions, which nest in the same way
that SRCU does.

This means that rcu_read_lock_trace() and rcu_read_unlock_trace()
will be with us for some time.  Therefore, remove the checkpatch.pl
deprecation.

Also, the rcu_read_lock_tasks_trace() and rcu_read_unlock_tasks_trace()
functions are intended for use only by BPF.  Therefore, add them to
the list of functions that checkpatch complains about outside of BPF
(and of course, RCU).

Reported-by: Puranjay Mohan <puranjay@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Joe Perches <joe@perches.com>
Cc: Dwaipayan Ray <dwaipayanray1@gmail.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
This commit is contained in:
Paul E. McKenney
2026-05-08 10:43:50 -07:00
committed by Uladzislau Rezki (Sony)
parent e2f08cefcf
commit 012c889690
1 changed files with 3 additions and 2 deletions
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5
scripts/checkpatch.pl
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@@ -865,8 +865,6 @@ our %deprecated_apis = (
"DEFINE_IDR" => "DEFINE_XARRAY",
"idr_init" => "xa_init",
"idr_init_base" => "xa_init_flags",
"rcu_read_lock_trace" => "rcu_read_lock_tasks_trace",
"rcu_read_unlock_trace" => "rcu_read_unlock_tasks_trace",
);
#Create a search pattern for all these strings to speed up a loop below
@@ -7596,12 +7594,15 @@ sub process {
# Complain about RCU Tasks Trace used outside of BPF (and of course, RCU).
our $rcu_trace_funcs = qr{(?x:
rcu_read_lock_tasks_trace |
rcu_read_lock_trace |
rcu_read_lock_trace_held |
rcu_read_unlock_trace |
rcu_read_unlock_tasks_trace |
call_rcu_tasks_trace |
synchronize_rcu_tasks_trace |
rcu_barrier_tasks_trace |
rcu_tasks_trace_expedite_current |
rcu_request_urgent_qs_task
)};
our $rcu_trace_paths = qr{(?x: