srcu: Check for invalid idx argument in srcu_read_unlock()

Paul E. McKenney · Paul E. McKenney · commit c8ca1aa774b2 · 2019-01-25T15:36:40.000-08:00
The current SRCU implementation has an idx argument of zero or one,
and never anything else.  This commit therefore adds a WARN_ON_ONCE()
to complain if this restriction is violated.

Signed-off-by: Paul E. McKenney &lt;paulmck@linux.ibm.com&gt;
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
@@ -223,6 +223,7 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp)
 static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx)
 	__releases(ssp)
 {
+	WARN_ON_ONCE(idx & ~0x1);
 	rcu_lock_release(&(ssp)->dep_map);
 	__srcu_read_unlock(ssp, idx);
 }

Original file line number	Diff line number	Diff line change
`@@ -223,6 +223,7 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp)`
`223`	`223`	`static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx)`
`224`	`224`	`__releases(ssp)`
`225`	`225`	`{`
	`226`	`+ WARN_ON_ONCE(idx & ~0x1);`
`226`	`227`	`rcu_lock_release(&(ssp)->dep_map);`
`227`	`228`	`__srcu_read_unlock(ssp, idx);`
`228`	`229`	`}`