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Commit b0a18cab authored by Gao Xiang's avatar Gao Xiang Committed by Greg Kroah-Hartman
Browse files

staging: erofs: atomic_cond_read_relaxed on ref-locked workgroup 



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: default avatarChao Yu <yuchao0@huawei.com>
Signed-off-by: default avatarGao Xiang <gaoxiang25@huawei.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 398102f6

drivers/staging/erofs/internal.h

+18 −12
Original line number Diff line number Diff line
@@ -211,23 +211,29 @@ 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;