If we do add the destructor hook, I think it looks like this.
It would merit some write-up in utrace.tmpl text too.
I'm not especially convinced it's a very good idea.
But I won't object if people serious about using the API think it helps.
Thanks,
Roland
---
include/linux/utrace.h | 8 ++++++++
kernel/utrace.c | 3 +++
2 files changed, 11 insertions(+), 0 deletions(-)
diff --git a/include/linux/utrace.h b/include/linux/utrace.h
index c19c01b..f968792 100644
--- a/include/linux/utrace.h
+++ b/include/linux/utrace.h
@@ -322,6 +322,7 @@ static inline enum utrace_syscall_action
utrace_syscall_action(u32 action)
struct utrace_engine {
/* private: */
struct kref kref;
+ void (*release)(void *);
struct list_head entry;
/* public: */
@@ -539,6 +540,12 @@ static inline void utrace_engine_put(struct utrace_engine
*engine)
* Unlike other callbacks, this can be called from the parent's context
* rather than from the traced thread itself--it must not delay the
* parent by blocking.
+ *
+ * @release:
+ * If not %NULL, this is called after the last utrace_engine_put()
+ * call for a &struct utrace_engine, which could be implicit after
+ * a %UTRACE_DETACH return from another callback. Its argument is
+ * the engine's @data member.
*/
struct utrace_engine_ops {
u32 (*report_quiesce)(enum utrace_resume_action action,
@@ -584,6 +591,7 @@ struct utrace_engine_ops {
bool group_dead, int signal);
void (*report_reap)(struct utrace_engine *engine,
struct task_struct *task);
+ void (*release)(void *data);
};
/**
diff --git a/kernel/utrace.c b/kernel/utrace.c
index 35be909..3b7ac74 100644
--- a/kernel/utrace.c
+++ b/kernel/utrace.c
@@ -79,6 +79,8 @@ void __utrace_engine_release(struct kref *kref)
struct utrace_engine *engine = container_of(kref, struct utrace_engine,
kref);
BUG_ON(!list_empty(&engine->entry));
+ if (engine->release)
+ (*engine->release)(engine->data);
kmem_cache_free(utrace_engine_cachep, engine);
}
EXPORT_SYMBOL_GPL(__utrace_engine_release);
@@ -271,6 +273,7 @@ struct utrace_engine *utrace_attach_task(
engine->flags = 0;
engine->ops = ops;
engine->data = data;
+ engine->release = ops->release;
ret = utrace_attach_delay(target);
if (likely(!ret))
