summaryrefslogtreecommitdiff
path: root/kernel/sched.c
diff options
context:
space:
mode:
authorGregory Haskins <ghaskins@novell.com>2008-06-04 15:04:05 -0400
committerIngo Molnar <mingo@elte.hu>2008-06-06 15:19:42 +0200
commit1f11eb6a8bc92536d9e93ead48fa3ffbd1478571 (patch)
tree40a123bd566bab8ddc726303e2725bae55b1a499 /kernel/sched.c
parent099f98c8a1f13501a98afbfff4756395a610581c (diff)
downloadlwn-1f11eb6a8bc92536d9e93ead48fa3ffbd1478571.tar.gz
lwn-1f11eb6a8bc92536d9e93ead48fa3ffbd1478571.zip
sched: fix cpupri hotplug support
The RT folks over at RedHat found an issue w.r.t. hotplug support which was traced to problems with the cpupri infrastructure in the scheduler: https://bugzilla.redhat.com/show_bug.cgi?id=449676 This bug affects 23-rt12+, 24-rtX, 25-rtX, and sched-devel. This patch applies to 25.4-rt4, though it should trivially apply to most cpupri enabled kernels mentioned above. It turned out that the issue was that offline cpus could get inadvertently registered with cpupri so that they were erroneously selected during migration decisions. The end result would be an OOPS as the offline cpu had tasks routed to it. This patch generalizes the old join/leave domain interface into an online/offline interface, and adjusts the root-domain/hotplug code to utilize it. I was able to easily reproduce the issue prior to this patch, and am no longer able to reproduce it after this patch. I can offline cpus indefinately and everything seems to be in working order. Thanks to Arnaldo (acme), Thomas, and Peter for doing the legwork to point me in the right direction. Also thank you to Peter for reviewing the early iterations of this patch. Signed-off-by: Gregory Haskins <ghaskins@novell.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/sched.c')
-rw-r--r--kernel/sched.c54
1 files changed, 40 insertions, 14 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index dc0be113f41d..f0ed81b71282 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -529,6 +529,7 @@ struct rq {
int push_cpu;
/* cpu of this runqueue: */
int cpu;
+ int online;
struct task_struct *migration_thread;
struct list_head migration_queue;
@@ -1498,6 +1499,8 @@ static void cfs_rq_set_shares(struct cfs_rq *cfs_rq, unsigned long shares)
#endif
#define sched_class_highest (&rt_sched_class)
+#define for_each_class(class) \
+ for (class = sched_class_highest; class; class = class->next)
static inline void inc_load(struct rq *rq, const struct task_struct *p)
{
@@ -6065,6 +6068,36 @@ static void unregister_sched_domain_sysctl(void)
}
#endif
+static void set_rq_online(struct rq *rq)
+{
+ if (!rq->online) {
+ const struct sched_class *class;
+
+ cpu_set(rq->cpu, rq->rd->online);
+ rq->online = 1;
+
+ for_each_class(class) {
+ if (class->rq_online)
+ class->rq_online(rq);
+ }
+ }
+}
+
+static void set_rq_offline(struct rq *rq)
+{
+ if (rq->online) {
+ const struct sched_class *class;
+
+ for_each_class(class) {
+ if (class->rq_offline)
+ class->rq_offline(rq);
+ }
+
+ cpu_clear(rq->cpu, rq->rd->online);
+ rq->online = 0;
+ }
+}
+
/*
* migration_call - callback that gets triggered when a CPU is added.
* Here we can start up the necessary migration thread for the new CPU.
@@ -6102,7 +6135,8 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
spin_lock_irqsave(&rq->lock, flags);
if (rq->rd) {
BUG_ON(!cpu_isset(cpu, rq->rd->span));
- cpu_set(cpu, rq->rd->online);
+
+ set_rq_online(rq);
}
spin_unlock_irqrestore(&rq->lock, flags);
break;
@@ -6163,7 +6197,7 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
spin_lock_irqsave(&rq->lock, flags);
if (rq->rd) {
BUG_ON(!cpu_isset(cpu, rq->rd->span));
- cpu_clear(cpu, rq->rd->online);
+ set_rq_offline(rq);
}
spin_unlock_irqrestore(&rq->lock, flags);
break;
@@ -6385,20 +6419,16 @@ sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
static void rq_attach_root(struct rq *rq, struct root_domain *rd)
{
unsigned long flags;
- const struct sched_class *class;
spin_lock_irqsave(&rq->lock, flags);
if (rq->rd) {
struct root_domain *old_rd = rq->rd;
- for (class = sched_class_highest; class; class = class->next) {
- if (class->leave_domain)
- class->leave_domain(rq);
- }
+ if (cpu_isset(rq->cpu, old_rd->online))
+ set_rq_offline(rq);
cpu_clear(rq->cpu, old_rd->span);
- cpu_clear(rq->cpu, old_rd->online);
if (atomic_dec_and_test(&old_rd->refcount))
kfree(old_rd);
@@ -6409,12 +6439,7 @@ static void rq_attach_root(struct rq *rq, struct root_domain *rd)
cpu_set(rq->cpu, rd->span);
if (cpu_isset(rq->cpu, cpu_online_map))
- cpu_set(rq->cpu, rd->online);
-
- for (class = sched_class_highest; class; class = class->next) {
- if (class->join_domain)
- class->join_domain(rq);
- }
+ set_rq_online(rq);
spin_unlock_irqrestore(&rq->lock, flags);
}
@@ -7824,6 +7849,7 @@ void __init sched_init(void)
rq->next_balance = jiffies;
rq->push_cpu = 0;
rq->cpu = i;
+ rq->online = 0;
rq->migration_thread = NULL;
INIT_LIST_HEAD(&rq->migration_queue);
rq_attach_root(rq, &def_root_domain);