linux-kernel - [PATCH] kernel: trace_syscalls: Replace rcu_assign_pointer() with RCU_INIT

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Date:	Fri, 22 Aug 2014 17:28:22 +0300
From:	Andreea-Cristina Bernat <bernat.ada@...il.com>
To:	rostedt@...dmis.org, mingo@...hat.com, linux-kernel@...r.kernel.org
Cc:	paulmck@...ux.vnet.ibm.com
Subject: [PATCH] kernel: trace_syscalls: Replace rcu_assign_pointer() with
 RCU_INIT_POINTER()

The uses of "rcu_assign_pointer()" are NULLing out the pointers.
According to RCU_INIT_POINTER()'s block comment:
"1.   This use of RCU_INIT_POINTER() is NULLing out the pointer"
it is better to use it instead of rcu_assign_pointer() because it has a
smaller overhead.

The following Coccinelle semantic patch was used:
@@
@@

- rcu_assign_pointer
+ RCU_INIT_POINTER
  (..., NULL)

Signed-off-by: Andreea-Cristina Bernat <bernat.ada@...il.com>
---
 kernel/trace/trace_syscalls.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 759d5e0..4dc8b79 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -425,7 +425,7 @@ static void unreg_event_syscall_enter(struct ftrace_event_file *file,
 		return;
 	mutex_lock(&syscall_trace_lock);
 	tr->sys_refcount_enter--;
-	rcu_assign_pointer(tr->enter_syscall_files[num], NULL);
+	RCU_INIT_POINTER(tr->enter_syscall_files[num], NULL);
 	if (!tr->sys_refcount_enter)
 		unregister_trace_sys_enter(ftrace_syscall_enter, tr);
 	mutex_unlock(&syscall_trace_lock);
@@ -463,7 +463,7 @@ static void unreg_event_syscall_exit(struct ftrace_event_file *file,
 		return;
 	mutex_lock(&syscall_trace_lock);
 	tr->sys_refcount_exit--;
-	rcu_assign_pointer(tr->exit_syscall_files[num], NULL);
+	RCU_INIT_POINTER(tr->exit_syscall_files[num], NULL);
 	if (!tr->sys_refcount_exit)
 		unregister_trace_sys_exit(ftrace_syscall_exit, tr);
 	mutex_unlock(&syscall_trace_lock);
-- 
1.9.1

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