Let's make sure that the one registering a workgroup will also
take the primary work lock at first for two reasons:
1) There's no need to introduce such a race window (and consequently
overhead) between registering and locking, other tasks could break
in by chance, and the race seems unnecessary (no benefit at all);
2) It's better to take the primary work when a workgroup
is registered to apply the cache managed policy, for example,
if some other tasks break in, it could turn into the in-place
decompression rather than use as the cached decompression.
Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx>
Signed-off-by: Gao Xiang <gaoxiang25@xxxxxxxxxx>
---
drivers/staging/erofs/unzip_vle.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/staging/erofs/unzip_vle.c b/drivers/staging/erofs/unzip_vle.c
index 4e5843e8ee35..a1376f3c6065 100644
--- a/drivers/staging/erofs/unzip_vle.c
+++ b/drivers/staging/erofs/unzip_vle.c
@@ -420,18 +420,22 @@ z_erofs_vle_work_register(const struct z_erofs_vle_work_finder *f,
work = z_erofs_vle_grab_primary_work(grp);
work->pageofs = f->pageofs;
+ /* lock all primary followed works before visible to others */
+ if (unlikely(!mutex_trylock(&work->lock)))
+ /* for a new workgroup, try_lock *never* fails */
+ DBG_BUGON(1);
+
if (gnew) {
int err = erofs_register_workgroup(f->sb, &grp->obj, 0);
if (err) {
+ mutex_unlock(&work->lock);
kmem_cache_free(z_erofs_workgroup_cachep, grp);
return ERR_PTR(-EAGAIN);
}
}
*f->owned_head = *f->grp_ret = grp;
-
- mutex_lock(&work->lock);
return work;
}
--
2.14.4
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