lkml.org 
[lkml]   [2010]   [Feb]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH tip/core/rcu 0/21] v6 add lockdep-based diagnostics to rcu_dereference()
Date
On Tuesday 23 February 2010, Paul E. McKenney wrote:
> We would also need something for initialization of structure fields.
> Does __force work in that case as well?

Yes, it will just need some syntactical sugar to avoid placing __force
in device drivers.

> > If there are cases where it does not work, we need to come up with
> > names for new primitives that just do the assignment or dereference
> > with __force but no actual synchronization.
>
> Some data structures are shared by RCU and non-RCU code, with struct
> list_head being the most prominent example. Making the "next" pointer
> as __rcu might be OK, but there are a -lot- of non-RCU uses of struct
> list_head. Would we really want to introduce rcu_dereference() to all
> non-RCU list-traversal primitives, or do we need to do something else?

I've just started an experimental implementation and got stuck at list rcu.
The two to deal with it that I can see are
- ignore list-rcu for now, and make all include/linux/rculist.h __force the
problem to be ignored.
- introduce a new struct rcu_list_head that needs to be used for list rcu.

A nicer option might be if sparse would let you write
'struct list_head __rcu head' and interpret that as having the pointers
inside it annotated as __rcu.

Arnd


\
 
 \ /
  Last update: 2010-02-23 18:19    [W:0.111 / U:0.068 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site