mirror of
https://github.com/linuxkit/linuxkit.git
synced 2025-10-31 20:19:50 +00:00
108 lines
3.1 KiB
Diff
108 lines
3.1 KiB
Diff
From 06e9e5bc8f89df6d839f2a1912efbd6a5867eac5 Mon Sep 17 00:00:00 2001
|
|
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
|
|
Date: Wed, 13 Sep 2017 14:43:41 +0200
|
|
Subject: [PATCH 380/414] srcu: use cpu_online() instead custom check
|
|
|
|
The current check via srcu_online is slightly racy because after looking
|
|
at srcu_online there could be an interrupt that interrupted us long
|
|
enough until the CPU we checked against went offline.
|
|
An alternative would be to hold the hotplug rwsem (so the CPUs don't
|
|
change their state) and then check based on cpu_online() if we queue it
|
|
on a specific CPU or not. queue_work_on() itself can handle if something
|
|
is enqueued on an offline CPU but a timer which is enqueued on an offline
|
|
CPU won't fire until the CPU is back online.
|
|
|
|
I am not sure if the removal in rcu_init() is okay or not. I assume that
|
|
SRCU won't enqueue a work item before SRCU is up and ready.
|
|
|
|
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
|
|
---
|
|
kernel/rcu/srcutree.c | 22 ++++------------------
|
|
kernel/rcu/tree.c | 6 ------
|
|
2 files changed, 4 insertions(+), 24 deletions(-)
|
|
|
|
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
|
|
index 6d5880089ff6..b72d8c552604 100644
|
|
--- a/kernel/rcu/srcutree.c
|
|
+++ b/kernel/rcu/srcutree.c
|
|
@@ -36,6 +36,7 @@
|
|
#include <linux/delay.h>
|
|
#include <linux/module.h>
|
|
#include <linux/srcu.h>
|
|
+#include <linux/cpu.h>
|
|
|
|
#include "rcu.h"
|
|
#include "rcu_segcblist.h"
|
|
@@ -424,21 +425,6 @@ static void srcu_gp_start(struct srcu_struct *sp)
|
|
WARN_ON_ONCE(state != SRCU_STATE_SCAN1);
|
|
}
|
|
|
|
-/*
|
|
- * Track online CPUs to guide callback workqueue placement.
|
|
- */
|
|
-DEFINE_PER_CPU(bool, srcu_online);
|
|
-
|
|
-void srcu_online_cpu(unsigned int cpu)
|
|
-{
|
|
- WRITE_ONCE(per_cpu(srcu_online, cpu), true);
|
|
-}
|
|
-
|
|
-void srcu_offline_cpu(unsigned int cpu)
|
|
-{
|
|
- WRITE_ONCE(per_cpu(srcu_online, cpu), false);
|
|
-}
|
|
-
|
|
/*
|
|
* Place the workqueue handler on the specified CPU if online, otherwise
|
|
* just run it whereever. This is useful for placing workqueue handlers
|
|
@@ -450,12 +436,12 @@ static bool srcu_queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
|
|
{
|
|
bool ret;
|
|
|
|
- preempt_disable();
|
|
- if (READ_ONCE(per_cpu(srcu_online, cpu)))
|
|
+ cpus_read_lock();
|
|
+ if (cpu_online(cpu))
|
|
ret = queue_delayed_work_on(cpu, wq, dwork, delay);
|
|
else
|
|
ret = queue_delayed_work(wq, dwork, delay);
|
|
- preempt_enable();
|
|
+ cpus_read_unlock();
|
|
return ret;
|
|
}
|
|
|
|
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
|
|
index 55c56b1aece7..85e2dc55a82c 100644
|
|
--- a/kernel/rcu/tree.c
|
|
+++ b/kernel/rcu/tree.c
|
|
@@ -3775,8 +3775,6 @@ int rcutree_online_cpu(unsigned int cpu)
|
|
{
|
|
sync_sched_exp_online_cleanup(cpu);
|
|
rcutree_affinity_setting(cpu, -1);
|
|
- if (IS_ENABLED(CONFIG_TREE_SRCU))
|
|
- srcu_online_cpu(cpu);
|
|
return 0;
|
|
}
|
|
|
|
@@ -3787,8 +3785,6 @@ int rcutree_online_cpu(unsigned int cpu)
|
|
int rcutree_offline_cpu(unsigned int cpu)
|
|
{
|
|
rcutree_affinity_setting(cpu, cpu);
|
|
- if (IS_ENABLED(CONFIG_TREE_SRCU))
|
|
- srcu_offline_cpu(cpu);
|
|
return 0;
|
|
}
|
|
|
|
@@ -4236,8 +4232,6 @@ void __init rcu_init(void)
|
|
for_each_online_cpu(cpu) {
|
|
rcutree_prepare_cpu(cpu);
|
|
rcu_cpu_starting(cpu);
|
|
- if (IS_ENABLED(CONFIG_TREE_SRCU))
|
|
- srcu_online_cpu(cpu);
|
|
}
|
|
}
|
|
|
|
--
|
|
2.17.0
|
|
|