Messages in this thread | | | Date | Thu, 20 Mar 2014 08:06:01 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 0/9] Replace rcu_assign_pointer(x, NULL) with RCU_INIT_POINTER(x,NULL) |
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On Thu, Mar 20, 2014 at 03:58:52PM +0100, Arend van Spriel wrote: > On 20/03/14 15:37, Monam Agarwal wrote: > >This patchset uses following coccinelle script to replace > >rcu_assign_pointer(x, NULL) with RCU_INIT_POINTER(x,NULL) > > > >@@ > >expression E; > >@@ > >- rcu_assign_pointer( > >+ RCU_INIT_POINTER( > >E, NULL) > > I am not very familiar with rcu functionality nor coccinelle, but it > looks too generic. I would think only NULL assignments during > initialization should use RCU_INIT_POINTER(). The first patch in the > series does it in a function called unregister_...(). Is it really > ok to do there?
Hello, Arend,
The thing that rcu_assign_pointer() is doing is ensuring that the initialization of a structure is carried out before storing a pointer to that structure. In the case of the NULL pointer, there is no structure to initialize, so nothing need be ordered.
So, yes, rcu_assign_pointer(p, NULL) can always safely be converted to RCU_INIT_POINTER(p, NULL). ;-)
Thanx, Paul
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