srcu: Debug NMI safety even on archs that don't require it

Currently the NMI safety debugging is only performed on architectures
that don't support NMI-safe this_cpu_inc().

Reorder the code so that other architectures like x86 also detect bad
uses.

[ paulmck: Apply kernel test robot, Stephen Rothwell, and Zqiang feedback. ]

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

1 files changed, 24 insertions, 12 deletions

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 1a7840c1b87a..f0814ffca34b 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -65,14 +65,14 @@ unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp);
 bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie);
 
 #ifdef CONFIG_NEED_SRCU_NMI_SAFE
-int __srcu_read_lock_nmisafe(struct srcu_struct *ssp, bool chknmisafe) __acquires(ssp);
-void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx, bool chknmisafe) __releases(ssp);
+int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp);
+void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases(ssp);
 #else
-static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp, bool chknmisafe)
+static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp)
 {
 	return __srcu_read_lock(ssp);
 }
-static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx, bool chknmisafe)
+static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
 {
 	__srcu_read_unlock(ssp, idx);
 }
@@ -118,6 +118,18 @@ static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
 
 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
+#define SRCU_NMI_UNKNOWN	0x0
+#define SRCU_NMI_UNSAFE		0x1
+#define SRCU_NMI_SAFE		0x2
+
+#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU)
+void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe);
+#else
+static inline void srcu_check_nmi_safety(struct srcu_struct *ssp,
+					 bool nmi_safe) { }
+#endif
+
+
 /**
  * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
  * @p: the pointer to fetch and protect for later dereferencing
@@ -175,6 +187,7 @@ static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp)
 {
 	int retval;
 
+	srcu_check_nmi_safety(ssp, false);
 	retval = __srcu_read_lock(ssp);
 	rcu_lock_acquire(&(ssp)->dep_map);
 	return retval;
@@ -191,10 +204,8 @@ static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp
 {
 	int retval;
 
-	if (IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE))
-		retval = __srcu_read_lock_nmisafe(ssp, true);
-	else
-		retval = __srcu_read_lock(ssp);
+	srcu_check_nmi_safety(ssp, true);
+	retval = __srcu_read_lock_nmisafe(ssp);
 	rcu_lock_acquire(&(ssp)->dep_map);
 	return retval;
 }
@@ -205,6 +216,7 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp)
 {
 	int retval;
 
+	srcu_check_nmi_safety(ssp, false);
 	retval = __srcu_read_lock(ssp);
 	return retval;
 }
@@ -220,6 +232,7 @@ static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx)
 	__releases(ssp)
 {
 	WARN_ON_ONCE(idx & ~0x1);
+	srcu_check_nmi_safety(ssp, false);
 	rcu_lock_release(&(ssp)->dep_map);
 	__srcu_read_unlock(ssp, idx);
 }
@@ -235,17 +248,16 @@ static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
 	__releases(ssp)
 {
 	WARN_ON_ONCE(idx & ~0x1);
+	srcu_check_nmi_safety(ssp, true);
 	rcu_lock_release(&(ssp)->dep_map);
-	if (IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE))
-		__srcu_read_unlock_nmisafe(ssp, idx, true);
-	else
-		__srcu_read_unlock(ssp, idx);
+	__srcu_read_unlock_nmisafe(ssp, idx);
 }
 
 /* Used by tracing, cannot be traced and cannot call lockdep. */
 static inline notrace void
 srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp)
 {
+	srcu_check_nmi_safety(ssp, false);
 	__srcu_read_unlock(ssp, idx);
 }