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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-09-11 02:29:02 +0300
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-10-06 21:16:18 +0300
commitc3ac7cf1847a4e68c909984f60d36adef2088e35 (patch)
tree42da217639fb90fe4e453ba88c7f809a8d05572b /include/linux/rcupdate.h
parentc34d2f418485a5d710bc002e490148b8ea53f456 (diff)
downloadlinux-c3ac7cf1847a4e68c909984f60d36adef2088e35.tar.xz
rcu: Add rcu_pointer_handoff()
This commit adds an rcu_pointer_handoff() that is intended to mark situations where a structure's protection transitions from RCU to some other mechanism (locking, reference counting, whatever). These markings should allow external tools to more easily spot bugs involving leaking pointers out of RCU read-side critical sections. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'include/linux/rcupdate.h')
-rw-r--r--include/linux/rcupdate.h22
1 files changed, 22 insertions, 0 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 6c3ceceb6148..587eb057e2fa 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -813,6 +813,28 @@ static inline void rcu_preempt_sleep_check(void)
#define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0)
/**
+ * rcu_pointer_handoff() - Hand off a pointer from RCU to other mechanism
+ * @p: The pointer to hand off
+ *
+ * This is simply an identity function, but it documents where a pointer
+ * is handed off from RCU to some other synchronization mechanism, for
+ * example, reference counting or locking. In C11, it would map to
+ * kill_dependency(). It could be used as follows:
+ *
+ * rcu_read_lock();
+ * p = rcu_dereference(gp);
+ * long_lived = is_long_lived(p);
+ * if (long_lived) {
+ * if (!atomic_inc_not_zero(p->refcnt))
+ * long_lived = false;
+ * else
+ * p = rcu_pointer_handoff(p);
+ * }
+ * rcu_read_unlock();
+ */
+#define rcu_pointer_handoff(p) (p)
+
+/**
* rcu_read_lock() - mark the beginning of an RCU read-side critical section
*
* When synchronize_rcu() is invoked on one CPU while other CPUs