linux-kernel - [PATCH RFC 2/5] trace: Use regular rcu_dereference

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Date:   Fri, 24 May 2019 19:49:30 -0400
From:   "Joel Fernandes (Google)" <joel@...lfernandes.org>
To:     linux-kernel@...r.kernel.org
Cc:     "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Ingo Molnar <mingo@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Josh Triplett <josh@...htriplett.org>, kvm-ppc@...r.kernel.org,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-doc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>,
        Paul Mackerras <paulus@...abs.org>, rcu@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH RFC 2/5] trace: Use regular rcu_dereference_raw API

rcu_dereference_raw already does not do any tracing. There is no need to
use the _notrace variant of it and this series removes that API, so let us
use the regular variant here.

While at it, also replace the only user of
hlist_for_each_entry_rcu_notrace (which indirectly uses the
rcu_dereference_raw_notrace API) with hlist_for_each_entry_rcu which
also does not do any tracing.

Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
---
 kernel/trace/ftrace.c          | 4 ++--
 kernel/trace/ftrace_internal.h | 8 ++++----
 kernel/trace/trace.c           | 4 ++--
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index b920358dd8f7..f7d5f0ee69de 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -706,7 +706,7 @@ ftrace_find_profiled_func(struct ftrace_profile_stat *stat, unsigned long ip)
 	if (hlist_empty(hhd))
 		return NULL;
 
-	hlist_for_each_entry_rcu_notrace(rec, hhd, node) {
+	hlist_for_each_entry_rcu(rec, hhd, node) {
 		if (rec->ip == ip)
 			return rec;
 	}
@@ -1135,7 +1135,7 @@ __ftrace_lookup_ip(struct ftrace_hash *hash, unsigned long ip)
 	key = ftrace_hash_key(hash, ip);
 	hhd = &hash->buckets[key];
 
-	hlist_for_each_entry_rcu_notrace(entry, hhd, hlist) {
+	hlist_for_each_entry_rcu(entry, hhd, hlist) {
 		if (entry->ip == ip)
 			return entry;
 	}
diff --git a/kernel/trace/ftrace_internal.h b/kernel/trace/ftrace_internal.h
index 0515a2096f90..e3530a284f46 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() 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() 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(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((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 ec439999f387..cb8d696d9cde 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2638,10 +2638,10 @@ static void ftrace_exports(struct ring_buffer_event *event)
 
 	preempt_disable_notrace();
 
-	export = rcu_dereference_raw_notrace(ftrace_exports_list);
+	export = rcu_dereference_raw(ftrace_exports_list);
 	while (export) {
 		trace_process_export(export, event);
-		export = rcu_dereference_raw_notrace(export->next);
+		export = rcu_dereference_raw(export->next);
 	}
 
 	preempt_enable_notrace();
-- 
2.22.0.rc1.257.g3120a18244-goog