lkml.org 
[lkml]   [2019]   [Feb]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.20 171/183] staging: erofs: atomic_cond_read_relaxed on ref-locked workgroup
Date
4.20-stable review patch.  If anyone has any objections, please let me know.

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

From: Gao Xiang <gaoxiang25@huawei.com>

commit df134b8d17b90c1e7720e318d36416b57424ff7a upstream.

It's better to use atomic_cond_read_relaxed, which is implemented
in hardware instructions to monitor a variable changes currently
for ARM64, instead of open-coded busy waiting.

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

---
drivers/staging/erofs/internal.h | 30 ++++++++++++++++++------------
1 file changed, 18 insertions(+), 12 deletions(-)

--- a/drivers/staging/erofs/internal.h
+++ b/drivers/staging/erofs/internal.h
@@ -221,23 +221,29 @@ static inline void erofs_workgroup_unfre
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 int erofs_wait_on_workgroup_freezed(struct erofs_workgroup *grp)
+{
+ int v = atomic_read(&grp->refcount);
+
+ /* workgroup is never freezed on uniprocessor systems */
+ DBG_BUGON(v == EROFS_LOCKED_MAGIC);
+ return v;
+}
+#endif
+
static inline bool erofs_workgroup_get(struct erofs_workgroup *grp, int *ocnt)
{
- const int locked = (int)EROFS_LOCKED_MAGIC;
int o;

repeat:
- o = atomic_read(&grp->refcount);
-
- /* spin if it is temporarily locked at the reclaim path */
- if (unlikely(o == locked)) {
-#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
- do
- cpu_relax();
- while (atomic_read(&grp->refcount) == locked);
-#endif
- goto repeat;
- }
+ o = erofs_wait_on_workgroup_freezed(grp);

if (unlikely(o <= 0))
return -1;

\
 
 \ /
  Last update: 2019-02-25 22:37    [W:0.455 / U:68.332 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site