Messages in this thread | | | Date | Tue, 12 Apr 2005 07:50:38 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 2/3] Keys: Use RCU to manage session keyring pointer |
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On Tue, Apr 12, 2005 at 10:11:50AM +0100, David Howells wrote: > Paul E. McKenney <paulmck@us.ibm.com> wrote: > > > > spin_lock_irqsave(&tsk->sighand->siglock, flags); > > > - old = tsk->signal->session_keyring; > > > - tsk->signal->session_keyring = keyring; > > > + old = rcu_dereference(tsk->signal->session_keyring); > > > > I don't understand why rcu_dereference() is needed in this case. > > Since we are holding the lock, it should not be possible for > > this to change, right? Or am I missing something? (Quite possible, > > am not all that familiar with this code.) > > Erm... you're right. I stuck the rcu_dereference() in then added the locks > back in when I realised I still needed them. > > > > + synchronize_kernel(); > > > > This would want to become synchronize_rcu(). > > I think the deprecation happened since I wrote my patch.
Yes, sorry, I should have made it clear that this was a change that affected your code rather than an error on your part.
> > > + if (tsk->signal->session_keyring) { > > > + rcu_read_lock(); > > > + key = keyring_search_aux( > > > + rcu_dereference(tsk->signal->session_keyring), > > > + type, description, match); > > > + rcu_read_unlock(); > > > + } > > > + else { > > > + key = keyring_search_aux(tsk->user->session_keyring, > > > + type, description, match); > > > > This one is constant, right? If not, I don't understand the locking design. > > Which one? tsk->user->session_keyring is, tsk->signal->session_keyring is not.
Good, that matches the code!
Thanx, Paul
> Thanks for the review. > > David > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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