lkml.org 
[lkml]   [2008]   [May]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] eCryptfs: Clean up kthread synchronization
On Thu, 22 May 2008 14:31:55 -0500
Michael Halcrow <mhalcrow@us.ibm.com> wrote:

> > > +void ecryptfs_destroy_kthread(void)
> > > +{
> > > + struct ecryptfs_open_req tmp_req;
> > > + struct ecryptfs_open_req *req;
> > > +
> > > + mutex_lock(&ecryptfs_kthread_ctl.mux);
> > > + ecryptfs_kthread_ctl.flags |= ECRYPTFS_KTHREAD_ZOMBIE;
> > > + list_for_each_entry(req, &ecryptfs_kthread_ctl.req_list,
> > > + kthread_ctl_list) {
> > > + mutex_lock(&req->mux);
> > > + req->flags |= ECRYPTFS_REQ_ZOMBIE;
> > > + wake_up_process(req->requesting_task);
> > > + mutex_unlock(&req->mux);
> > > + }
> > > + memset(&tmp_req, 0, sizeof(tmp_req));
> > > + tmp_req.flags = ECRYPTFS_REQ_ZOMBIE;
> > > + list_add_tail(&tmp_req.kthread_ctl_list,
> > > + &ecryptfs_kthread_ctl.req_list);
> > > + mutex_unlock(&ecryptfs_kthread_ctl.mux);
> > > + wake_up(&ecryptfs_kthread_ctl.wait);
> > > +}
> >
> > eh? We attach a local variable to a global list and then return?
> > That won't last very long.
>
> Adding this dummy entry to the list is just my own way of getting the
> kthread to wake up and shut down. This actually works, albeit a little
> ugly. The list and its contents get dropped on the floor at this point
> because (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE). The
> only consumer of this list (the kthread) checks for this flag
> immediately after getting the mux, and if it is there, it just
> exits. The only producer on this list (ecryptfs_privileged_open())
> checks for this flag immediately after getting the mux and bows out if
> it is set. In other words, once this flag is set, the list and its
> contents become untouchable by anything other than
> ecryptfs_destroy_kthread().

Unconvinced.

As soon as ecryptfs_destroy_kthread() returns, tmp_req is destroyed.
But it remains on ecryptfs_kthread_ctl.req_list.

> memset(&tmp_req, 0, sizeof(tmp_req));
> tmp_req.flags = ECRYPTFS_REQ_ZOMBIE;
> list_add_tail(&tmp_req.kthread_ctl_list,
> &ecryptfs_kthread_ctl.req_list);
> mutex_unlock(&ecryptfs_kthread_ctl.mux);
> wake_up(&ecryptfs_kthread_ctl.wait);

-> it's dead.

> }



\
 
 \ /
  Last update: 2008-05-22 21:45    [W:0.050 / U:0.212 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site