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 <[email protected]> Signed-off-by: Paul E. McKenney <[email protected]> Cc: Andy Whitcroft <[email protected]> Cc: Joe Perches <[email protected]> Cc: Dwaipayan Ray <[email protected]> Cc: Lukas Bulwahn <[email protected]> --- scripts/checkpatch.pl | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index 0492d6afc9a1fc..cc5bbd70cb843e 100755 --- a/scripts/checkpatch.pl +++ b/scripts/checkpatch.pl @@ -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: -- 2.40.1
