[PATCH 16/19] introduce task_utrace_lock/task_utrace_unlock
- Add task_utrace_lock(task). It simply takes task->utrace->lock if
this task was ever utraced. Otherwise it takes task_lock(), this
serializes with utrace_attach_task()->utrace_task_alloc(). In both
case the caller can be sure it can't race with anything which needs
utrace->lock.
- Add task_utrace_unlock(task), it releases the corresponding lock.
Signed-off-by: Oleg Nesterov <oleg(a)redhat.com>
---
include/linux/utrace.h | 9 +++++++++
kernel/utrace.c | 26 ++++++++++++++++++++++++++
2 files changed, 35 insertions(+), 0 deletions(-)
diff --git a/include/linux/utrace.h b/include/linux/utrace.h
index f251efe..5176f5f 100644
--- a/include/linux/utrace.h
+++ b/include/linux/utrace.h
@@ -109,6 +109,12 @@ void utrace_signal_handler(struct task_struct *, int);
#ifndef CONFIG_UTRACE
+static inline void task_utrace_lock(struct task_struct *task)
+{
+}
+static inline void task_utrace_unlock(struct task_struct *task)
+{
+}
/*
* <linux/tracehook.h> uses these accessors to avoid #ifdef CONFIG_UTRACE.
*/
@@ -131,6 +137,9 @@ static inline void task_utrace_proc_status(struct seq_file *m,
#else /* CONFIG_UTRACE */
+extern void task_utrace_lock(struct task_struct *task);
+extern void task_utrace_unlock(struct task_struct *task);
+
static inline unsigned long task_utrace_flags(struct task_struct *task)
{
return task->utrace_flags;
diff --git a/kernel/utrace.c b/kernel/utrace.c
index a824ac3..508c13c 100644
--- a/kernel/utrace.c
+++ b/kernel/utrace.c
@@ -79,6 +79,32 @@ static int __init utrace_init(void)
}
module_init(utrace_init);
+void task_utrace_lock(struct task_struct *task)
+{
+ struct utrace *utrace = task_utrace_struct(task);
+
+ if (!utrace) {
+ task_lock(task);
+ utrace = task_utrace_struct(task);
+ if (!utrace)
+ return;
+
+ task_unlock(task);
+ }
+
+ spin_lock(&utrace->lock);
+}
+
+void task_utrace_unlock(struct task_struct *task)
+{
+ struct utrace *utrace = task_utrace_struct(task);
+
+ if (utrace)
+ spin_unlock(&utrace->lock);
+ else
+ task_unlock(task);
+}
+
/*
* Set up @task.utrace for the first time. We can have races
* between two utrace_attach_task() calls here. The task_lock()
--
1.5.5.1