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Date: Thu, 17 Jul 2014 16:40:27 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Pranith Kumar <bobby.prani@...il.com> Cc: Josh Triplett <josh@...htriplett.org>, Steven Rostedt <rostedt@...dmis.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Lai Jiangshan <laijs@...fujitsu.com>, "open list:READ-COPY UPDATE..." <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 1/1] rcu: Remove redundant checks for rcu_scheduler_fully_active On Tue, Jul 15, 2014 at 09:50:02PM -0400, Pranith Kumar wrote: > rcu_scheduler_fully_active is set to true early in the boot process. > > rcu_prepare_kthreads() is called in two locations. Once after setting the above > flag and the other while hotplugging a CPU from rcu_cpu_notify(). CPU hotplug is > enabled much later by which time the above flag is already set. Hence checking > for this flag is redundant in this function. > > The checks in rcu_spawn_one_boost_kthread() and rcu_spawn_all_nocb_kthreads() > are similarly redundant. > > This commit removes the redundant checks for this flag from the above > locations. > > Signed-off-by: Pranith Kumar <bobby.prani@...il.com> Good catch! Queued for 3.18. Thanx, Paul > --- > kernel/rcu/tree_plugin.h | 10 ++++------ > 1 file changed, 4 insertions(+), 6 deletions(-) > > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > index 17ccb62..a2113f6 100644 > --- a/kernel/rcu/tree_plugin.h > +++ b/kernel/rcu/tree_plugin.h > @@ -1341,7 +1341,7 @@ static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp, > if (&rcu_preempt_state != rsp) > return 0; > > - if (!rcu_scheduler_fully_active || rnp->qsmaskinit == 0) > + if (rnp->qsmaskinit == 0) > return 0; > > rsp->boost = 1; > @@ -1489,8 +1489,7 @@ static void rcu_prepare_kthreads(int cpu) > struct rcu_node *rnp = rdp->mynode; > > /* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */ > - if (rcu_scheduler_fully_active) > - (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); > + (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); > } > > #else /* #ifdef CONFIG_RCU_BOOST */ > @@ -2509,9 +2508,8 @@ static void rcu_spawn_all_nocb_kthreads(int cpu) > { > struct rcu_state *rsp; > > - if (rcu_scheduler_fully_active) > - for_each_rcu_flavor(rsp) > - rcu_spawn_one_nocb_kthread(rsp, cpu); > + for_each_rcu_flavor(rsp) > + rcu_spawn_one_nocb_kthread(rsp, cpu); > } > > /* > -- > 1.9.1 > -- 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/
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