linux-kernel - Re: [PATCH tip/core/rcu 13/15] rcu: Introduce for_each_rcu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 15 Jun 2012 22:35:00 -0700
From:	Josh Triplett <josh@...htriplett.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, eric.dumazet@...il.com, darren@...art.com,
	fweisbec@...il.com, patches@...aro.org
Subject: Re: [PATCH tip/core/rcu 13/15] rcu: Introduce for_each_rcu_flavor()
 and use it

On Fri, Jun 15, 2012 at 06:01:49PM -0700, Paul E. McKenney wrote:
> On Fri, Jun 15, 2012 at 04:52:40PM -0700, Josh Triplett wrote:
> > On Fri, Jun 15, 2012 at 02:06:08PM -0700, Paul E. McKenney wrote:
> > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> > > index bd4e41c..75ad92a 100644
> > > --- a/kernel/rcutree.c
> > > +++ b/kernel/rcutree.c
> > > @@ -84,6 +84,7 @@ struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, call_rcu_bh);
> > >  DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
> > >  
> > >  static struct rcu_state *rcu_state;
> > > +LIST_HEAD(rcu_struct_flavors);
> > 
> > Does any means exist to turn this into a constant array known at compile
> > time rather than a runtime linked list?  Having this as a compile-time
> > constant may allow the compiler to unroll for_each_rcu_flavor and
> > potentially inline the calls inside it.
> 
> I could do that, but none of the traversals is anywhere near performance
> critical, and all the ways I can think of to do this are uglier than
> the list.

All of the struct rcu_state instances exist at compile time, so you can
just create an array of pointers to them:

static struct rcu_state *const rcu_struct_flavors[] = {
    &rcu_data,
    &rcu_bh_data,
#ifdef CONFIG_TREE_PREEMPT_RCU
    &rcu_preempt_data,
#endif
};

Then just define for_each_rcu_flavor to iterate over that compile-time
constant array.  Any reason that wouldn't work?

- Josh Triplett
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/