On 03/20/14 16:06, Paul E. McKenney wrote:
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). ;-)
And so I learned something today. Thanks, Paul. I really should pick up
reading rcu material again. It ended up in a dusty corner upstairs.
Thanks,
Arend
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