On Fri, Nov 30, 2007 at 04:37:21PM -0800, Paul E. McKenney wrote: > > The rcu_assign_pointer() primitive currently unconditionally executes > a memory barrier, even when a NULL pointer is being assigned. This > has lead some to avoid using rcu_assign_pointer() for NULL pointers, > which loses the self-documenting advantages of rcu_assign_pointer() > This patch uses __builtin_const_p() to omit needless memory barriers > for NULL-pointer assignments at compile time with no runtime penalty, > as discussed in the following thread: > > http://www.mail-archive.com/netdev@xxxxxxxxxxxxxxx/msg54852.html > > Tested on x86_64 and ppc64, also compiled the four cases (NULL/non-NULL > and const/non-const) with gcc version 4.1.2, and hand-checked the > assembly output. > > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> Acked-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Thanks a lot for following through with this Paul! -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt _______________________________________________ Bridge mailing list Bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/bridge
