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Subject[RFC PATCH 4/5] RCU: Add TASK_RCU_OFFSET


We can not include linux/sched.h in linux/rcupdate.h.
If we access task's task_rcu_strut without linux/sched.h included,
We will failed with compiling error.

So we add TASK_RCU_OFFSET, which help us access
task's task_rcu_strut without linux/sched.h included.
Now, task_rcu_struct(), current_task_rcu_struct(), task_of_task_rcu() and
rcu_copy_process() can be used anywhere without linux/sched.h included.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
include/linux/rcupdate.h | 49 +++++++++++++++++++++++++++++++++++++++++----
kernel/kernel-offsets.c | 3 ++
2 files changed, 47 insertions(+), 5 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 3500138..a5ed3fe 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -140,11 +140,50 @@ static inline void init_task_rcu_struct(struct task_rcu_struct *task_rcu)
#endif
}

-#define task_rcu_struct(t) (&(t)->task_rcu_struct)
-#define current_task_rcu_struct() task_rcu_struct(current)
-#define task_of_task_rcu(task_rcu) container_of(task_rcu, struct task_struct,\
- task_rcu_struct)
-#define rcu_copy_process(tsk) init_task_rcu_struct(task_rcu_struct(tsk))
+#ifdef __KBUILD_GENARATING__
+/*
+ * Very eary kbuild stage, many important defines including TASK_RCU_OFFSET
+ * are not available, use dummies to avoid compiling errors.
+ */
+static inline
+struct task_rcu_struct *task_rcu_struct(struct task_struct *t)
+{
+ (void)t;
+ return (struct task_rcu_struct *)0x3L;
+}
+
+static inline
+struct task_struct *task_of_task_rcu(struct task_rcu_struct *task_rcu)
+{
+ (void)task_rcu;
+ return (struct task_struct *)-0x3L;
+}
+#else
+/* for generated TASK_RCU_OFFSET */
+#include <generated/kernel-offsets.h>
+
+static inline
+struct task_rcu_struct *task_rcu_struct(struct task_struct *t)
+{
+ return (struct task_rcu_struct *)(((void *)t) + TASK_RCU_OFFSET);
+}
+
+static inline
+struct task_struct *task_of_task_rcu(struct task_rcu_struct *task_rcu)
+{
+ return (struct task_struct *)(((void *)task_rcu) - TASK_RCU_OFFSET);
+}
+#endif
+
+static inline struct task_rcu_struct *current_task_rcu_struct(void)
+{
+ return task_rcu_struct(current);
+}
+
+static inline void rcu_copy_process(struct task_struct *tsk)
+{
+ init_task_rcu_struct(task_rcu_struct(tsk));
+}

#ifdef CONFIG_PREEMPT_RCU

diff --git a/kernel/kernel-offsets.c b/kernel/kernel-offsets.c
index fb73ccf..a890511 100644
--- a/kernel/kernel-offsets.c
+++ b/kernel/kernel-offsets.c
@@ -4,11 +4,14 @@
* Copyright (C) 2010 Lai Jiangshan
*/

+#include <linux/rcupdate.h>
+#include <linux/sched.h>
#include <linux/kbuild.h>

void foo(void);

void foo(void)
{
+ OFFSET(TASK_RCU_OFFSET, task_struct, task_rcu_struct);
}

--
1.7.4


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