diff options
| author |   Gao Xiang <gaoxiang25@huawei.com> | 2018-11-23 01:16:01 +0800 |
|---|---|---|
| committer |   Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-11-23 10:53:07 +0100 |
| commit | df134b8d17b90c1e7720e318d36416b57424ff7a (patch) | |
| tree | 29618c9a3dab4808d557d8309927e64a85e98f19 | |
| parent | staging: erofs: fix race when the managed cache is enabled (diff) | |
staging: erofs: atomic_cond_read_relaxed on ref-locked workgroup
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>
| -rw-r--r-- | drivers/staging/erofs/internal.h | 30 |
1 files changed, 18 insertions, 12 deletions
diff --git a/drivers/staging/erofs/internal.h b/drivers/staging/erofs/internal.h index 3ac4599bbe01..f933ab602c37 100644 --- a/drivers/staging/erofs/internal.h +++ b/drivers/staging/erofs/internal.h @@ -221,23 +221,29 @@ static inline void erofs_workgroup_unfreeze( 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; |