This commit documents the implicit RCU readers that are implied by the
this_cpu_inc() and atomic_long_inc() operations in __srcu_read_lock_fast()
and __srcu_read_unlock_fast(). While in the area, fix the documentation
of the memory pairing of atomic_long_inc() in __srcu_read_lock_fast().
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: <bpf@xxxxxxxxxxxxxxx>
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 043b5a67ef71e..78e1a7b845ba9 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -245,9 +245,9 @@ static inline struct srcu_ctr __percpu *__srcu_read_lock_fast(struct srcu_struct
struct srcu_ctr __percpu *scp = READ_ONCE(ssp->srcu_ctrp);
if (!IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE))
- this_cpu_inc(scp->srcu_locks.counter); /* Y */
+ this_cpu_inc(scp->srcu_locks.counter); // Y, and implicit RCU reader.
else
- atomic_long_inc(raw_cpu_ptr(&scp->srcu_locks)); /* Z */
+ atomic_long_inc(raw_cpu_ptr(&scp->srcu_locks)); // Y, and implicit RCU reader.
barrier(); /* Avoid leaking the critical section. */
return scp;
}
@@ -271,9 +271,9 @@ static inline void __srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_
{
barrier(); /* Avoid leaking the critical section. */
if (!IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE))
- this_cpu_inc(scp->srcu_unlocks.counter); /* Z */
+ this_cpu_inc(scp->srcu_unlocks.counter); // Z, and implicit RCU reader.
else
- atomic_long_inc(raw_cpu_ptr(&scp->srcu_unlocks)); /* Z */
+ atomic_long_inc(raw_cpu_ptr(&scp->srcu_unlocks)); // Z, and implicit RCU reader.
}
void __srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor);
