Re: [PATCH] Remove rcu_assign_pointer() penalty for NULL pointers

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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

[Index of Archives]     [Netdev]     [AoE Tools]     [Linux Wireless]     [Kernel Newbies]     [Security]     [Linux for Hams]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux RAID]     [Linux Admin]     [Samba]     [Video 4 Linux]

  Powered by Linux