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
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
>
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[PATCH 1/1] rcu: Remove redundant checks for rcu_scheduler_fully_active
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
---
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
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