Messages in this thread Patch in this message | | | From | Gao Xiang <> | Subject | [PATCH 08/10] staging: erofs: locked before registering for all new workgroups | Date | Tue, 20 Nov 2018 22:34:23 +0800 |
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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@huawei.com> Signed-off-by: Gao Xiang <gaoxiang25@huawei.com> --- 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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