Subject: Re: [PATCH] treewide: Rename rcu_dereference_raw_notrace to _check

From: "Paul E. McKenney" <[email-masked]>
Date: Fri, 12 Jul 2019 08:01:07 -0700

On Thu, Jul 11, 2019 at 04:45:41PM -0400, Joel Fernandes (Google) wrote:
> The rcu_dereference_raw_notrace() API name is confusing.
> It is equivalent to rcu_dereference_raw() except that it also does
> sparse pointer checking.
> 
> There are only a few users of rcu_dereference_raw_notrace(). This
> patches renames all of them to be rcu_dereference_raw_check with the
> "check" indicating sparse checking.
> 
> Signed-off-by: Joel Fernandes (Google) <[email-masked]>

I queued this, but reworked the commit log and fixed a couple of
irritating checkpatch issues that were in the original code.
Does this work for you?

							Thanx, Paul

------------------------------------------------------------------------

commit bd5c0fea6016c90cf7a9eb0435cd0c373dfdac2f
Author: Joel Fernandes (Google) <[email-masked]>
Date:   Thu Jul 11 16:45:41 2019 -0400

    treewide: Rename rcu_dereference_raw_notrace() to _check()
    
    The rcu_dereference_raw_notrace() API name is confusing.  It is equivalent
    to rcu_dereference_raw() except that it also does sparse pointer checking.
    
    There are only a few users of rcu_dereference_raw_notrace(). This patches
    renames all of them to be rcu_dereference_raw_check() with the "_check()"
    indicating sparse checking.
    
    Signed-off-by: Joel Fernandes (Google) <[email-masked]>
    [ paulmck: Fix checkpatch warnings about parentheses. ]
    Signed-off-by: Paul E. McKenney <[email-masked]>

diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html
index f04c467e55c5..467251f7fef6 100644
--- a/Documentation/RCU/Design/Requirements/Requirements.html
+++ b/Documentation/RCU/Design/Requirements/Requirements.html
@@ -2514,7 +2514,7 @@ disabled across the entire RCU read-side critical section.
 <p>
 It is possible to use tracing on RCU code, but tracing itself
 uses RCU.
-For this reason, <tt>rcu_dereference_raw_notrace()</tt>
+For this reason, <tt>rcu_dereference_raw_check()</tt>
 is provided for use by tracing, which avoids the destructive
 recursion that could otherwise ensue.
 This API is also used by virtualization in some architectures,
diff --git a/arch/powerpc/include/asm/kvm_book3s_64.h b/arch/powerpc/include/asm/kvm_book3s_64.h
index 21b1ed5df888..53388a311967 100644
--- a/arch/powerpc/include/asm/kvm_book3s_64.h
+++ b/arch/powerpc/include/asm/kvm_book3s_64.h
@@ -546,7 +546,7 @@ static inline void note_hpte_modification(struct kvm *kvm,
  */
 static inline struct kvm_memslots *kvm_memslots_raw(struct kvm *kvm)
 {
-	return rcu_dereference_raw_notrace(kvm->memslots[0]);
+	return rcu_dereference_raw_check(kvm->memslots[0]);
 }
 
 extern void kvmppc_mmu_debugfs_init(struct kvm *kvm);
diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index e91ec9ddcd30..932296144131 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -622,7 +622,7 @@ static inline void hlist_add_behind_rcu(struct hlist_node *n,
  * 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)),\
+	for (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(\
@@ -642,10 +642,10 @@ static inline void hlist_add_behind_rcu(struct hlist_node *n,
  * not do any RCU debugging or tracing.
  */
 #define hlist_for_each_entry_rcu_notrace(pos, head, member)			\
-	for (pos = hlist_entry_safe (rcu_dereference_raw_notrace(hlist_first_rcu(head)),\
+	for (pos = hlist_entry_safe(rcu_dereference_raw_check(hlist_first_rcu(head)),\
 			typeof(*(pos)), member);			\
 		pos;							\
-		pos = hlist_entry_safe(rcu_dereference_raw_notrace(hlist_next_rcu(\
+		pos = hlist_entry_safe(rcu_dereference_raw_check(hlist_next_rcu(\
 			&(pos)->member)), typeof(*(pos)), member))
 
 /**
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 0c9b92799abc..e5161e377ad4 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -478,7 +478,7 @@ do {									      \
  * The no-tracing version of rcu_dereference_raw() must not call
  * rcu_read_lock_held().
  */
-#define rcu_dereference_raw_notrace(p) __rcu_dereference_check((p), 1, __rcu)
+#define rcu_dereference_raw_check(p) __rcu_dereference_check((p), 1, __rcu)
 
 /**
  * rcu_dereference_protected() - fetch RCU pointer when updates prevented
diff --git a/kernel/trace/ftrace_internal.h b/kernel/trace/ftrace_internal.h
index 0515a2096f90..0456e0a3dab1 100644
--- a/kernel/trace/ftrace_internal.h
+++ b/kernel/trace/ftrace_internal.h
@@ -6,22 +6,22 @@
 
 /*
  * Traverse the ftrace_global_list, invoking all entries.  The reason that we
- * can use rcu_dereference_raw_notrace() is that elements removed from this list
+ * can use rcu_dereference_raw_check() is that elements removed from this list
  * are simply leaked, so there is no need to interact with a grace-period
- * mechanism.  The rcu_dereference_raw_notrace() calls are needed to handle
+ * mechanism.  The rcu_dereference_raw_check() calls are needed to handle
  * concurrent insertions into the ftrace_global_list.
  *
  * Silly Alpha and silly pointer-speculation compiler optimizations!
  */
 #define do_for_each_ftrace_op(op, list)			\
-	op = rcu_dereference_raw_notrace(list);			\
+	op = rcu_dereference_raw_check(list);			\
 	do
 
 /*
  * Optimized for just a single item in the list (as that is the normal case).
  */
 #define while_for_each_ftrace_op(op)				\
-	while (likely(op = rcu_dereference_raw_notrace((op)->next)) &&	\
+	while (likely(op = rcu_dereference_raw_check((op)->next)) &&	\
 	       unlikely((op) != &ftrace_list_end))
 
 extern struct ftrace_ops __rcu *ftrace_ops_list;
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 2c92b3d9ea30..1d69110d9e5b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2642,10 +2642,10 @@ static void ftrace_exports(struct ring_buffer_event *event)
 
 	preempt_disable_notrace();
 
-	export = rcu_dereference_raw_notrace(ftrace_exports_list);
+	export = rcu_dereference_raw_check(ftrace_exports_list);
 	while (export) {
 		trace_process_export(export, event);
-		export = rcu_dereference_raw_notrace(export->next);
+		export = rcu_dereference_raw_check(export->next);
 	}
 
 	preempt_enable_notrace();