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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>
This commit is contained in:
Gao Xiang 2018-11-23 01:16:01 +08:00 committed by Greg Kroah-Hartman
parent 51232df5e4
commit df134b8d17
1 changed files with 18 additions and 12 deletions
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30
drivers/staging/erofs/internal.h
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@ -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;