staging: erofs: fix `erofs_workgroup_{try_to_freeze, unfreeze}'

There are two minor issues in the current freeze interface:

   1) Freeze interfaces have not related with CONFIG_DEBUG_SPINLOCK,
      therefore fix the incorrect conditions;

   2) For SMP platforms, it should also disable preemption before
      doing atomic_cmpxchg in case that some high priority tasks
      preempt between atomic_cmpxchg and disable_preempt, then spin
      on the locked refcount later.

Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/erofs/internal.h b/drivers/staging/erofs/internal.h
index f933ab602c3704ef3514a96bc3a4d1f7e1eb30a7..399a7003e783eabdc4d0472220a05de8a94ec629 100644 (file)
--- a/drivers/staging/erofs/internal.h
+++ b/drivers/staging/erofs/internal.h
@@ -194,40 +194,49 @@ struct erofs_workgroup {
 
 #define EROFS_LOCKED_MAGIC     (INT_MIN | 0xE0F510CCL)
 
-static inline bool erofs_workgroup_try_to_freeze(
-       struct erofs_workgroup *grp, int v)
+#if defined(CONFIG_SMP)
+static inline bool erofs_workgroup_try_to_freeze(struct erofs_workgroup *grp,
+                                                int val)
 {
-#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
-       if (v != atomic_cmpxchg(&grp->refcount,
-               v, EROFS_LOCKED_MAGIC))
-               return false;
        preempt_disable();
-#else
-       preempt_disable();
-       if (atomic_read(&grp->refcount) != v) {
+       if (val != atomic_cmpxchg(&grp->refcount, val, EROFS_LOCKED_MAGIC)) {
                preempt_enable();
                return false;
        }
-#endif
        return true;
 }
 
-static inline void erofs_workgroup_unfreeze(
-       struct erofs_workgroup *grp, int v)
+static inline void erofs_workgroup_unfreeze(struct erofs_workgroup *grp,
+                                           int orig_val)
 {
-#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
-       atomic_set(&grp->refcount, v);
-#endif
+       atomic_set(&grp->refcount, orig_val);
        preempt_enable();
 }
 
-#if defined(CONFIG_SMP)
 static inline int erofs_wait_on_workgroup_freezed(struct erofs_workgroup *grp)
 {
        return atomic_cond_read_relaxed(&grp->refcount,
                                        VAL != EROFS_LOCKED_MAGIC);
 }
 #else
+static inline bool erofs_workgroup_try_to_freeze(struct erofs_workgroup *grp,
+                                                int val)
+{
+       preempt_disable();
+       /* no need to spin on UP platforms, let's just disable preemption. */
+       if (val != atomic_read(&grp->refcount)) {
+               preempt_enable();
+               return false;
+       }
+       return true;
+}
+
+static inline void erofs_workgroup_unfreeze(struct erofs_workgroup *grp,
+                                           int orig_val)
+{
+       preempt_enable();
+}
+
 static inline int erofs_wait_on_workgroup_freezed(struct erofs_workgroup *grp)
 {
        int v = atomic_read(&grp->refcount);