On Tue, Nov 20, 2018 at 10:34:17PM +0800, Gao Xiang wrote: > When the managed cache is enabled, the last reference count > of a workgroup must be used for its workstation. > > Otherwise, it could lead to incorrect (un)freezes in > the reclaim path, and it would be harmful. > > A typical race as follows: > > Thread 1 (In the reclaim path) Thread 2 > workgroup_freeze(grp, 1) refcnt = 1 > ... > workgroup_unfreeze(grp, 1) refcnt = 1 > workgroup_get(grp) refcnt = 2 (x) > workgroup_put(grp) refcnt = 1 (x) > ...unexpected behaviors > > * grp is detached but still used, which violates cache-managed > freeze constraint. > > Reviewed-by: Chao Yu <yuchao0@xxxxxxxxxx> > Signed-off-by: Gao Xiang <gaoxiang25@xxxxxxxxxx> > --- > drivers/staging/erofs/internal.h | 1 + > drivers/staging/erofs/utils.c | 131 +++++++++++++++++++++++++++------------ > 2 files changed, 93 insertions(+), 39 deletions(-) > > diff --git a/drivers/staging/erofs/internal.h b/drivers/staging/erofs/internal.h > index 57575c7f5635..89dbd0888e53 100644 > --- a/drivers/staging/erofs/internal.h > +++ b/drivers/staging/erofs/internal.h > @@ -250,6 +250,7 @@ static inline bool erofs_workgroup_get(struct erofs_workgroup *grp, int *ocnt) > } > > #define __erofs_workgroup_get(grp) atomic_inc(&(grp)->refcount) > +#define __erofs_workgroup_put(grp) atomic_dec(&(grp)->refcount) Any specific reason why you are not using the refcount.h api instead of "doing it yourself" with atomic_inc/dec()? I'm not rejecting this, just curious. thanks, greg k-h _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
