[RFC PATCH 1/1] rcu: Consolidate kthread launches
Hi Paul,
I looked at why my previous change removing checks for
rcu_scheduler_fully_active failed to boot.
The reason is that rcu_init() is called earlier than rest_init() from within
which the early_init() is being called. rcu_init() calls rcu_cpu_notify() which
in turn calls rcu_spawn_all_nocb_kthread().
This patch does the following:
* since we are launching other threads now from rcu_spawn_gp_kthread() rename it
to rcu_spawn_kthreads()
* move nocb kthread launches on cpu hotplug to rcu_prepare_kthreads(), the name
is generic so thre is no need to rename ;)
* check whether CPU is a no-CB CPU before calling rcu_spawn_all_nocb_kthreads()
on that CPU
I've got the KVM rcutorture setup running and verified these changes.
Side note: we should probably change the trace comment for rcu_cpu_notify()
which says it is for Hotplug :)
Signed-off-by: Pranith Kumar
---
kernel/rcu/tree.c| 8
kernel/rcu/tree_plugin.h | 19 ---
2 files changed, 16 insertions(+), 11 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 72e0b1f..2866464 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3451,7 +3451,6 @@ static int rcu_cpu_notify(struct notifier_block *self,
case CPU_UP_PREPARE_FROZEN:
rcu_prepare_cpu(cpu);
rcu_prepare_kthreads(cpu);
- rcu_spawn_all_nocb_kthreads(cpu);
break;
case CPU_ONLINE:
case CPU_DOWN_FAILED:
@@ -3499,9 +3498,10 @@ static int rcu_pm_notify(struct notifier_block *self,
}
/*
- * Spawn the kthreads that handle each RCU flavor's grace periods.
+ * Spawn the kthreads that handle each RCU flavor's grace periods
+ * and the no-CB and boost kthreads.
*/
-static int __init rcu_spawn_gp_kthread(void)
+static int __init rcu_spawn_kthreads(void)
{
unsigned long flags;
struct rcu_node *rnp;
@@ -3521,7 +3521,7 @@ static int __init rcu_spawn_gp_kthread(void)
rcu_spawn_boost_kthreads();
return 0;
}
-early_initcall(rcu_spawn_gp_kthread);
+early_initcall(rcu_spawn_kthreads);
/*
* This function is invoked towards the end of the scheduler's initialization
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index eaa32e4..42e113b 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1339,7 +1339,7 @@ static int rcu_spawn_one_boost_kthread(struct rcu_state
*rsp,
if (_preempt_state != rsp)
return 0;
- if (!rcu_scheduler_fully_active || rnp->qsmaskinit == 0)
+ if (rnp->qsmaskinit == 0)
return 0;
rsp->boost = 1;
@@ -1486,9 +1486,14 @@ static void rcu_prepare_kthreads(int cpu)
struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu);
struct rcu_node *rnp = rdp->mynode;
+ if (!rcu_scheduler_fully_active)
+ return;
+
/* 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);
+
+ if (rcu_is_nocb_cpu(cpu))
+ rcu_spawn_all_nocb_kthreads(cpu);
}
#else /* #ifdef CONFIG_RCU_BOOST */
@@ -2507,9 +2512,8 @@ 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);
}
/*
@@ -2523,7 +2527,8 @@ static void __init rcu_spawn_nocb_kthreads(void)
int cpu;
for_each_online_cpu(cpu)
- rcu_spawn_all_nocb_kthreads(cpu);
+ if (rcu_is_nocb_cpu(cpu))
+ rcu_spawn_all_nocb_kthreads(cpu);
}
/* How many follower CPU IDs per leader? Default of -1 for sqrt(nr_cpu_ids).
*/
--
1.9.1
--
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[RFC PATCH 1/1] rcu: Consolidate kthread launches
Hi Paul,
I looked at why my previous change removing checks for
rcu_scheduler_fully_active failed to boot.
The reason is that rcu_init() is called earlier than rest_init() from within
which the early_init() is being called. rcu_init() calls rcu_cpu_notify() which
in turn calls rcu_spawn_all_nocb_kthread().
This patch does the following:
* since we are launching other threads now from rcu_spawn_gp_kthread() rename it
to rcu_spawn_kthreads()
* move nocb kthread launches on cpu hotplug to rcu_prepare_kthreads(), the name
is generic so thre is no need to rename ;)
* check whether CPU is a no-CB CPU before calling rcu_spawn_all_nocb_kthreads()
on that CPU
I've got the KVM rcutorture setup running and verified these changes.
Side note: we should probably change the trace comment for rcu_cpu_notify()
which says it is for Hotplug :)
Signed-off-by: Pranith Kumar bobby.pr...@gmail.com
---
kernel/rcu/tree.c| 8
kernel/rcu/tree_plugin.h | 19 ---
2 files changed, 16 insertions(+), 11 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 72e0b1f..2866464 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3451,7 +3451,6 @@ static int rcu_cpu_notify(struct notifier_block *self,
case CPU_UP_PREPARE_FROZEN:
rcu_prepare_cpu(cpu);
rcu_prepare_kthreads(cpu);
- rcu_spawn_all_nocb_kthreads(cpu);
break;
case CPU_ONLINE:
case CPU_DOWN_FAILED:
@@ -3499,9 +3498,10 @@ static int rcu_pm_notify(struct notifier_block *self,
}
/*
- * Spawn the kthreads that handle each RCU flavor's grace periods.
+ * Spawn the kthreads that handle each RCU flavor's grace periods
+ * and the no-CB and boost kthreads.
*/
-static int __init rcu_spawn_gp_kthread(void)
+static int __init rcu_spawn_kthreads(void)
{
unsigned long flags;
struct rcu_node *rnp;
@@ -3521,7 +3521,7 @@ static int __init rcu_spawn_gp_kthread(void)
rcu_spawn_boost_kthreads();
return 0;
}
-early_initcall(rcu_spawn_gp_kthread);
+early_initcall(rcu_spawn_kthreads);
/*
* This function is invoked towards the end of the scheduler's initialization
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index eaa32e4..42e113b 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1339,7 +1339,7 @@ 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;
@@ -1486,9 +1486,14 @@ static void rcu_prepare_kthreads(int cpu)
struct rcu_data *rdp = per_cpu_ptr(rcu_state_p-rda, cpu);
struct rcu_node *rnp = rdp-mynode;
+ if (!rcu_scheduler_fully_active)
+ return;
+
/* 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);
+
+ if (rcu_is_nocb_cpu(cpu))
+ rcu_spawn_all_nocb_kthreads(cpu);
}
#else /* #ifdef CONFIG_RCU_BOOST */
@@ -2507,9 +2512,8 @@ 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);
}
/*
@@ -2523,7 +2527,8 @@ static void __init rcu_spawn_nocb_kthreads(void)
int cpu;
for_each_online_cpu(cpu)
- rcu_spawn_all_nocb_kthreads(cpu);
+ if (rcu_is_nocb_cpu(cpu))
+ rcu_spawn_all_nocb_kthreads(cpu);
}
/* How many follower CPU IDs per leader? Default of -1 for sqrt(nr_cpu_ids).
*/
--
1.9.1
--
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