[PATCH 4.19 141/152] staging: erofs: add a full barrier in erofs_workgroup_unfreeze

From: Greg Kroah-Hartman
Date: Mon Feb 25 2019 - 16:47:18 EST


4.19-stable review patch. If anyone has any objections, please let me know.

------------------

From: Gao Xiang <gaoxiang25@xxxxxxxxxx>

commit 948bbdb1818b7ad6e539dad4fbd2dd4650793ea9 upstream.

Just like other generic locks, insert a full barrier
in case of memory reorder.

Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>
Signed-off-by: Gao Xiang <gaoxiang25@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
drivers/staging/erofs/internal.h | 5 +++++
1 file changed, 5 insertions(+)

--- a/drivers/staging/erofs/internal.h
+++ b/drivers/staging/erofs/internal.h
@@ -199,6 +199,11 @@ static inline bool erofs_workgroup_try_t
static inline void erofs_workgroup_unfreeze(struct erofs_workgroup *grp,
int orig_val)
{
+ /*
+ * other observers should notice all modifications
+ * in the freezing period.
+ */
+ smp_mb();
atomic_set(&grp->refcount, orig_val);
preempt_enable();
}