From: Gao Xiang <gaoxiang25@xxxxxxxxxx>
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 | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/staging/erofs/unzip_vle.c b/drivers/staging/erofs/unzip_vle.c
index 4e5843e8ee35..6aa3c989dd4e 100644
--- a/drivers/staging/erofs/unzip_vle.c
+++ b/drivers/staging/erofs/unzip_vle.c
@@ -420,18 +420,23 @@ 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
+ * and mutex_trylock *never* fails for a new workgroup.
+ */
+ mutex_trylock(&work->lock);
+
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;
}
--
2.11.0
_______________________________________________
devel mailing list
devel@xxxxxxxxxxxxxxxxxxxxxx
http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
