On Mon, Mar 18, 2019 at 03:26:34PM +0800, Gao Xiang wrote: > commit 51232df5e4b268936beccde5248f312a316800be upstream. > > 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> > --- > > change log v3: > - avoid using xa_tag apis since Matthew refuses the first XArray patch > in the previous version again; > > RESEND in order to ping due to lack of response from Matthew and Greg > for half a month, patch 2/2 is needed to be backported to linux-4.19. I've queued this up now, thanks. greg k-h
