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    SubjectRe: [PATCH tip/core/rcu 05/14] rcu: Distinguish "rcuo" kthreads by RCU flavor
    On Sun, Jan 06, 2013 at 06:34:17PM -0500, Paul Gortmaker wrote:
    > On Sat, Jan 5, 2013 at 12:48 PM, Paul E. McKenney
    > <paulmck@linux.vnet.ibm.com> wrote:
    > > From: "Paul E. McKenney" <paul.mckenney@linaro.org>
    > >
    > > Currently, the per-no-CBs-CPU kthreads are named "rcuo" followed by
    > > the CPU number, for example, "rcuo". This is problematic given that
    > > there are either two or three RCU flavors, each of which gets a per-CPU
    > > kthread with exactly the same name. This commit therefore introduces
    > > a one-letter abbreviation for each RCU flavor, namely 'b' for RCU-bh,
    > > 'p' for RCU-preempt, and 's' for RCU-sched. This abbreviation use used
    > > to distinguish the "rcuo" kthreads, for example, for CPU 0 we would have
    > > "rcuo0b", "rcuo0p", and "rcuo0s".
    >
    > Since these names are exposed to Joe Average when he runs ps/top
    > etc. -- I am inclined to favour the more full names as implemented
    > in this older patch:
    >
    > http://goo.gl/H1Aj8
    >
    > ...since "rcuo0p" isn't apt to mean anything to people outside
    > of the to/cc list of this mail. (Catch me off guard, and I probably
    > might fail to be able to name the three flavours myself...)
    >
    > But then again it is just a personal preference. In any case, if we stick
    > with the short names in your patch, we probably still should make the
    > similar two documentation type chunks from my patch in yours.

    I took yours and Josh's advice here, so the names are now rcuoX/N,
    with the definitions of X and N in both the Kconfig entry and in
    Documentation/kernel-parameters.txt.

    Thanx, Paul

    > Paul.
    > --
    >
    > >
    > > Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
    > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    > > Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
    > > ---
    > > kernel/rcutree.c | 7 ++++---
    > > kernel/rcutree.h | 1 +
    > > kernel/rcutree_plugin.h | 5 +++--
    > > 3 files changed, 8 insertions(+), 5 deletions(-)
    > >
    > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c
    > > index 8b110fa..4ec797e 100644
    > > --- a/kernel/rcutree.c
    > > +++ b/kernel/rcutree.c
    > > @@ -64,7 +64,7 @@
    > > static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
    > > static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
    > >
    > > -#define RCU_STATE_INITIALIZER(sname, cr) { \
    > > +#define RCU_STATE_INITIALIZER(sname, sabbr, cr) { \
    > > .level = { &sname##_state.node[0] }, \
    > > .call = cr, \
    > > .fqs_state = RCU_GP_IDLE, \
    > > @@ -76,13 +76,14 @@ static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
    > > .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
    > > .onoff_mutex = __MUTEX_INITIALIZER(sname##_state.onoff_mutex), \
    > > .name = #sname, \
    > > + .abbr = sabbr, \
    > > }
    > >
    > > struct rcu_state rcu_sched_state =
    > > - RCU_STATE_INITIALIZER(rcu_sched, call_rcu_sched);
    > > + RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
    > > DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
    > >
    > > -struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, call_rcu_bh);
    > > +struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh);
    > > DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
    > >
    > > static struct rcu_state *rcu_state;
    > > diff --git a/kernel/rcutree.h b/kernel/rcutree.h
    > > index ef26eab..c865117 100644
    > > --- a/kernel/rcutree.h
    > > +++ b/kernel/rcutree.h
    > > @@ -452,6 +452,7 @@ struct rcu_state {
    > > unsigned long gp_max; /* Maximum GP duration in */
    > > /* jiffies. */
    > > char *name; /* Name of structure. */
    > > + char abbr; /* Abbreviated name. */
    > > struct list_head flavors; /* List of RCU flavors. */
    > > };
    > >
    > > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
    > > index eb9b473..ab1bdde 100644
    > > --- a/kernel/rcutree_plugin.h
    > > +++ b/kernel/rcutree_plugin.h
    > > @@ -111,7 +111,7 @@ static void __init rcu_bootup_announce_oddness(void)
    > > #ifdef CONFIG_TREE_PREEMPT_RCU
    > >
    > > struct rcu_state rcu_preempt_state =
    > > - RCU_STATE_INITIALIZER(rcu_preempt, call_rcu);
    > > + RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu);
    > > DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data);
    > > static struct rcu_state *rcu_state = &rcu_preempt_state;
    > >
    > > @@ -2510,7 +2510,8 @@ static void __init rcu_spawn_nocb_kthreads(struct rcu_state *rsp)
    > > return;
    > > for_each_cpu(cpu, rcu_nocb_mask) {
    > > rdp = per_cpu_ptr(rsp->rda, cpu);
    > > - t = kthread_run(rcu_nocb_kthread, rdp, "rcuo%d", cpu);
    > > + t = kthread_run(rcu_nocb_kthread, rdp,
    > > + "rcuo%d%c", cpu, rsp->abbr);
    > > BUG_ON(IS_ERR(t));
    > > ACCESS_ONCE(rdp->nocb_kthread) = t;
    > > }
    > > --
    > > 1.7.8
    > >
    > > --
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    > > the body of a message to majordomo@vger.kernel.org
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