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authorMichael S. Tsirkin <mst@redhat.com>2013-11-05 00:36:17 +0400
committerGleb Natapov <gleb@redhat.com>2013-11-06 11:32:09 +0400
commitce332f662deb545c8a4f3f58debcca26bb2e44b0 (patch)
tree20af98a6c78d1c95033ef1a67caec18d97862e54 /include/linux/srcu.h
parent80f5b5e700fa9c58480eafce0d47367bafb70006 (diff)
downloadlinux-ce332f662deb545c8a4f3f58debcca26bb2e44b0.tar.xz
srcu: API for barrier after srcu read unlock
srcu read lock/unlock include a full memory barrier but that's an implementation detail. Add an API for make memory fencing explicit for users that need this barrier, to make sure we can change it as needed without breaking all users. Acked-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
Diffstat (limited to 'include/linux/srcu.h')
-rw-r--r--include/linux/srcu.h14
1 files changed, 14 insertions, 0 deletions
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index c114614ed172..9b058eecd403 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -237,4 +237,18 @@ static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
__srcu_read_unlock(sp, idx);
}
+/**
+ * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
+ *
+ * Converts the preceding srcu_read_unlock into a two-way memory barrier.
+ *
+ * Call this after srcu_read_unlock, to guarantee that all memory operations
+ * that occur after smp_mb__after_srcu_read_unlock will appear to happen after
+ * the preceding srcu_read_unlock.
+ */
+static inline void smp_mb__after_srcu_read_unlock(void)
+{
+ /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
+}
+
#endif