[v2,2/9] rcu: Add support for consolidated-RCU reader checking
diff mbox series

Message ID 20190712170024.111093-3-joel@joelfernandes.org
State New
Headers show
Series
  • Harden list_for_each_entry_rcu() and family
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Commit Message

Joel Fernandes July 12, 2019, 5 p.m. UTC
This patch adds support for checking RCU reader sections in list
traversal macros. Optionally, if the list macro is called under SRCU or
other lock/mutex protection, then appropriate lockdep expressions can be
passed to make the checks pass.

Existing list_for_each_entry_rcu() invocations don't need to pass the
optional fourth argument (cond) unless they are under some non-RCU
protection and needs to make lockdep check pass.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 include/linux/rculist.h  | 28 +++++++++++++++++++++++-----
 include/linux/rcupdate.h |  7 +++++++
 kernel/rcu/Kconfig.debug | 11 +++++++++++
 kernel/rcu/update.c      | 14 ++++++++++++++
 4 files changed, 55 insertions(+), 5 deletions(-)

Comments

Paul E. McKenney July 16, 2019, 6:22 p.m. UTC | #1
On Fri, Jul 12, 2019 at 01:00:17PM -0400, Joel Fernandes (Google) wrote:
> This patch adds support for checking RCU reader sections in list
> traversal macros. Optionally, if the list macro is called under SRCU or
> other lock/mutex protection, then appropriate lockdep expressions can be
> passed to make the checks pass.
> 
> Existing list_for_each_entry_rcu() invocations don't need to pass the
> optional fourth argument (cond) unless they are under some non-RCU
> protection and needs to make lockdep check pass.
> 
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>

If you fold in the checks for extra parameters, I will take this
one and also 1/9.

							Thanx, Paul

> ---
>  include/linux/rculist.h  | 28 +++++++++++++++++++++++-----
>  include/linux/rcupdate.h |  7 +++++++
>  kernel/rcu/Kconfig.debug | 11 +++++++++++
>  kernel/rcu/update.c      | 14 ++++++++++++++
>  4 files changed, 55 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/rculist.h b/include/linux/rculist.h
> index e91ec9ddcd30..1048160625bb 100644
> --- a/include/linux/rculist.h
> +++ b/include/linux/rculist.h
> @@ -40,6 +40,20 @@ static inline void INIT_LIST_HEAD_RCU(struct list_head *list)
>   */
>  #define list_next_rcu(list)	(*((struct list_head __rcu **)(&(list)->next)))
>  
> +/*
> + * Check during list traversal that we are within an RCU reader
> + */
> +
> +#ifdef CONFIG_PROVE_RCU_LIST
> +#define __list_check_rcu(dummy, cond, ...)				\
> +	({								\
> +	RCU_LOCKDEP_WARN(!cond && !rcu_read_lock_any_held(),		\
> +			 "RCU-list traversed in non-reader section!");	\
> +	 })
> +#else
> +#define __list_check_rcu(dummy, cond, ...) ({})
> +#endif
> +
>  /*
>   * Insert a new entry between two known consecutive entries.
>   *
> @@ -343,14 +357,16 @@ static inline void list_splice_tail_init_rcu(struct list_head *list,
>   * @pos:	the type * to use as a loop cursor.
>   * @head:	the head for your list.
>   * @member:	the name of the list_head within the struct.
> + * @cond:	optional lockdep expression if called from non-RCU protection.
>   *
>   * This list-traversal primitive may safely run concurrently with
>   * the _rcu list-mutation primitives such as list_add_rcu()
>   * as long as the traversal is guarded by rcu_read_lock().
>   */
> -#define list_for_each_entry_rcu(pos, head, member) \
> -	for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \
> -		&pos->member != (head); \
> +#define list_for_each_entry_rcu(pos, head, member, cond...)		\
> +	for (__list_check_rcu(dummy, ## cond, 0),			\
> +	     pos = list_entry_rcu((head)->next, typeof(*pos), member);	\
> +		&pos->member != (head);					\
>  		pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
>  
>  /**
> @@ -616,13 +632,15 @@ static inline void hlist_add_behind_rcu(struct hlist_node *n,
>   * @pos:	the type * to use as a loop cursor.
>   * @head:	the head for your list.
>   * @member:	the name of the hlist_node within the struct.
> + * @cond:	optional lockdep expression if called from non-RCU protection.
>   *
>   * This list-traversal primitive may safely run concurrently with
>   * the _rcu list-mutation primitives such as hlist_add_head_rcu()
>   * as long as the traversal is guarded by rcu_read_lock().
>   */
> -#define hlist_for_each_entry_rcu(pos, head, member)			\
> -	for (pos = hlist_entry_safe (rcu_dereference_raw(hlist_first_rcu(head)),\
> +#define hlist_for_each_entry_rcu(pos, head, member, cond...)		\
> +	for (__list_check_rcu(dummy, ## cond, 0),			\
> +	     pos = hlist_entry_safe (rcu_dereference_raw(hlist_first_rcu(head)),\
>  			typeof(*(pos)), member);			\
>  		pos;							\
>  		pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(\
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 922bb6848813..712b464ab960 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -223,6 +223,7 @@ int debug_lockdep_rcu_enabled(void);
>  int rcu_read_lock_held(void);
>  int rcu_read_lock_bh_held(void);
>  int rcu_read_lock_sched_held(void);
> +int rcu_read_lock_any_held(void);
>  
>  #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
>  
> @@ -243,6 +244,12 @@ static inline int rcu_read_lock_sched_held(void)
>  {
>  	return !preemptible();
>  }
> +
> +static inline int rcu_read_lock_any_held(void)
> +{
> +	return !preemptible();
> +}
> +
>  #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
>  
>  #ifdef CONFIG_PROVE_RCU
> diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
> index 0ec7d1d33a14..b20d0e2903d1 100644
> --- a/kernel/rcu/Kconfig.debug
> +++ b/kernel/rcu/Kconfig.debug
> @@ -7,6 +7,17 @@ menu "RCU Debugging"
>  config PROVE_RCU
>  	def_bool PROVE_LOCKING
>  
> +config PROVE_RCU_LIST
> +	bool "RCU list lockdep debugging"
> +	depends on PROVE_RCU
> +	default n
> +	help
> +	  Enable RCU lockdep checking for list usages. By default it is
> +	  turned off since there are several list RCU users that still
> +	  need to be converted to pass a lockdep expression. To prevent
> +	  false-positive splats, we keep it default disabled but once all
> +	  users are converted, we can remove this config option.
> +
>  config TORTURE_TEST
>  	tristate
>  	default n
> diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
> index bb961cd89e76..0cc7be0fb6b5 100644
> --- a/kernel/rcu/update.c
> +++ b/kernel/rcu/update.c
> @@ -294,6 +294,20 @@ int rcu_read_lock_bh_held(void)
>  }
>  EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
>  
> +int rcu_read_lock_any_held(void)
> +{
> +	if (!debug_lockdep_rcu_enabled())
> +		return 1;
> +	if (!rcu_is_watching())
> +		return 0;
> +	if (!rcu_lockdep_current_cpu_online())
> +		return 0;
> +	if (lock_is_held(&rcu_lock_map) || lock_is_held(&rcu_sched_lock_map))
> +		return 1;
> +	return !preemptible();
> +}
> +EXPORT_SYMBOL_GPL(rcu_read_lock_any_held);
> +
>  #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
>  
>  /**
> -- 
> 2.22.0.510.g264f2c817a-goog
>
Joel Fernandes July 16, 2019, 6:35 p.m. UTC | #2
On Tue, Jul 16, 2019 at 11:22:37AM -0700, Paul E. McKenney wrote:
> On Fri, Jul 12, 2019 at 01:00:17PM -0400, Joel Fernandes (Google) wrote:
> > This patch adds support for checking RCU reader sections in list
> > traversal macros. Optionally, if the list macro is called under SRCU or
> > other lock/mutex protection, then appropriate lockdep expressions can be
> > passed to make the checks pass.
> > 
> > Existing list_for_each_entry_rcu() invocations don't need to pass the
> > optional fourth argument (cond) unless they are under some non-RCU
> > protection and needs to make lockdep check pass.
> > 
> > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> 
> If you fold in the checks for extra parameters, I will take this
> one and also 1/9.

I folded the checks in and also threw in the rcu-sync with Oleg's ack:

Could you pull into /dev branch?

git pull https://github.com/joelagnel/linux-kernel.git list-first-three
(Based on your dev branch)
Paul E. McKenney July 16, 2019, 6:50 p.m. UTC | #3
On Tue, Jul 16, 2019 at 02:35:17PM -0400, Joel Fernandes wrote:
> On Tue, Jul 16, 2019 at 11:22:37AM -0700, Paul E. McKenney wrote:
> > On Fri, Jul 12, 2019 at 01:00:17PM -0400, Joel Fernandes (Google) wrote:
> > > This patch adds support for checking RCU reader sections in list
> > > traversal macros. Optionally, if the list macro is called under SRCU or
> > > other lock/mutex protection, then appropriate lockdep expressions can be
> > > passed to make the checks pass.
> > > 
> > > Existing list_for_each_entry_rcu() invocations don't need to pass the
> > > optional fourth argument (cond) unless they are under some non-RCU
> > > protection and needs to make lockdep check pass.
> > > 
> > > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> > 
> > If you fold in the checks for extra parameters, I will take this
> > one and also 1/9.
> 
> I folded the checks in and also threw in the rcu-sync with Oleg's ack:
> 
> Could you pull into /dev branch?
> 
> git pull https://github.com/joelagnel/linux-kernel.git list-first-three
> (Based on your dev branch)

Given that I am going to have to rebase these a few times, please
email a v4.

							Thanx, Paul

Patch
diff mbox series

diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index e91ec9ddcd30..1048160625bb 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -40,6 +40,20 @@  static inline void INIT_LIST_HEAD_RCU(struct list_head *list)
  */
 #define list_next_rcu(list)	(*((struct list_head __rcu **)(&(list)->next)))
 
+/*
+ * Check during list traversal that we are within an RCU reader
+ */
+
+#ifdef CONFIG_PROVE_RCU_LIST
+#define __list_check_rcu(dummy, cond, ...)				\
+	({								\
+	RCU_LOCKDEP_WARN(!cond && !rcu_read_lock_any_held(),		\
+			 "RCU-list traversed in non-reader section!");	\
+	 })
+#else
+#define __list_check_rcu(dummy, cond, ...) ({})
+#endif
+
 /*
  * Insert a new entry between two known consecutive entries.
  *
@@ -343,14 +357,16 @@  static inline void list_splice_tail_init_rcu(struct list_head *list,
  * @pos:	the type * to use as a loop cursor.
  * @head:	the head for your list.
  * @member:	the name of the list_head within the struct.
+ * @cond:	optional lockdep expression if called from non-RCU protection.
  *
  * This list-traversal primitive may safely run concurrently with
  * the _rcu list-mutation primitives such as list_add_rcu()
  * as long as the traversal is guarded by rcu_read_lock().
  */
-#define list_for_each_entry_rcu(pos, head, member) \
-	for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \
-		&pos->member != (head); \
+#define list_for_each_entry_rcu(pos, head, member, cond...)		\
+	for (__list_check_rcu(dummy, ## cond, 0),			\
+	     pos = list_entry_rcu((head)->next, typeof(*pos), member);	\
+		&pos->member != (head);					\
 		pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
 
 /**
@@ -616,13 +632,15 @@  static inline void hlist_add_behind_rcu(struct hlist_node *n,
  * @pos:	the type * to use as a loop cursor.
  * @head:	the head for your list.
  * @member:	the name of the hlist_node within the struct.
+ * @cond:	optional lockdep expression if called from non-RCU protection.
  *
  * This list-traversal primitive may safely run concurrently with
  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
  * as long as the traversal is guarded by rcu_read_lock().
  */
-#define hlist_for_each_entry_rcu(pos, head, member)			\
-	for (pos = hlist_entry_safe (rcu_dereference_raw(hlist_first_rcu(head)),\
+#define hlist_for_each_entry_rcu(pos, head, member, cond...)		\
+	for (__list_check_rcu(dummy, ## cond, 0),			\
+	     pos = hlist_entry_safe (rcu_dereference_raw(hlist_first_rcu(head)),\
 			typeof(*(pos)), member);			\
 		pos;							\
 		pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(\
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 922bb6848813..712b464ab960 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -223,6 +223,7 @@  int debug_lockdep_rcu_enabled(void);
 int rcu_read_lock_held(void);
 int rcu_read_lock_bh_held(void);
 int rcu_read_lock_sched_held(void);
+int rcu_read_lock_any_held(void);
 
 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
@@ -243,6 +244,12 @@  static inline int rcu_read_lock_sched_held(void)
 {
 	return !preemptible();
 }
+
+static inline int rcu_read_lock_any_held(void)
+{
+	return !preemptible();
+}
+
 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
 #ifdef CONFIG_PROVE_RCU
diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
index 0ec7d1d33a14..b20d0e2903d1 100644
--- a/kernel/rcu/Kconfig.debug
+++ b/kernel/rcu/Kconfig.debug
@@ -7,6 +7,17 @@  menu "RCU Debugging"
 config PROVE_RCU
 	def_bool PROVE_LOCKING
 
+config PROVE_RCU_LIST
+	bool "RCU list lockdep debugging"
+	depends on PROVE_RCU
+	default n
+	help
+	  Enable RCU lockdep checking for list usages. By default it is
+	  turned off since there are several list RCU users that still
+	  need to be converted to pass a lockdep expression. To prevent
+	  false-positive splats, we keep it default disabled but once all
+	  users are converted, we can remove this config option.
+
 config TORTURE_TEST
 	tristate
 	default n
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index bb961cd89e76..0cc7be0fb6b5 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -294,6 +294,20 @@  int rcu_read_lock_bh_held(void)
 }
 EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
 
+int rcu_read_lock_any_held(void)
+{
+	if (!debug_lockdep_rcu_enabled())
+		return 1;
+	if (!rcu_is_watching())
+		return 0;
+	if (!rcu_lockdep_current_cpu_online())
+		return 0;
+	if (lock_is_held(&rcu_lock_map) || lock_is_held(&rcu_sched_lock_map))
+		return 1;
+	return !preemptible();
+}
+EXPORT_SYMBOL_GPL(rcu_read_lock_any_held);
+
 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
 /**