Re: CPU Hotplug broken -mm5 onwards

Andrew Morton
2004-04-22T07:03:54Z

Srivatsa Vaddagiri <vatsa@in.ibm.com> wrote:
>
> Anyway patch below addresses the above races. Its against 2.6.6-rc2-mm1
> and has been tested on a 4way Intel Pentium SMP m/c. I have added a
> cpu_is_offlince check in migration_thread(). If that is true, migration
> thread stop processing and just waits for kthread_stop.

I'll take the stunned silence as agreement ;)

It needed a warning fixup:

kernel/sched.c: In function `migration_call':
kernel/sched.c:3648: warning: unused variable `tmp'
kernel/sched.c:3648: warning: unused variable `req'
kernel/sched.c:3647: warning: unused variable `head'

---

25-akpm/kernel/sched.c | 44 ++++++++++++++++++++++++--------------------
1 files changed, 24 insertions(+), 20 deletions(-)

diff -puN kernel/sched.c~sched-remove_hotplug_lock_in_sched_migrate_task-warnings kernel/sched.c
--- 25/kernel/sched.c~sched-remove_hotplug_lock_in_sched_migrate_task-warnings 2004-04-21 23:56:43.736745848 -0700
+++ 25-akpm/kernel/sched.c 2004-04-21 23:58:42.628671528 -0700
@@ -3339,8 +3339,6 @@ static int migration_call(struct notifie
struct task_struct *p;
struct runqueue *rq;
unsigned long flags;
- struct list_head *head;
- migration_req_t *req, *tmp;

switch (action) {
case CPU_UP_PREPARE:
@@ -3363,25 +3361,31 @@ static int migration_call(struct notifie
/* Unbind it from offline cpu so it can run. Fall thru. */
kthread_bind(cpu_rq(cpu)->migration_thread,smp_processor_id());
case CPU_DEAD:
- rq = cpu_rq(cpu);
- head = &rq->migration_queue;
- spin_lock_irq(&rq->lock);
- list_for_each_entry_safe(req, tmp, head, list) {
-
- BUG_ON(req->type != REQ_MOVE_TASK);
-
- list_del_init(&req->list);
-
- /* No need to migrate the task in the request. It would
- * have already been migrated (maybe to a different
- * CPU). Just wake up the requestor.
- */
- complete(&req->done);
+ {
+ struct list_head *head;
+ migration_req_t *req, *tmp;
+
+ rq = cpu_rq(cpu);
+ head = &rq->migration_queue;
+ spin_lock_irq(&rq->lock);
+ list_for_each_entry_safe(req, tmp, head, list) {
+
+ BUG_ON(req->type != REQ_MOVE_TASK);
+
+ list_del_init(&req->list);
+
+ /*
+ * No need to migrate the task in the request.
+ * It would have already been migrated (maybe to
+ * a different CPU). Just wake up the requestor
+ */
+ complete(&req->done);
+ }
+ spin_unlock_irq(&rq->lock);
+ kthread_stop(cpu_rq(cpu)->migration_thread);
+ cpu_rq(cpu)->migration_thread = NULL;
+ BUG_ON(cpu_rq(cpu)->nr_running != 0);
}
- spin_unlock_irq(&rq->lock);
- kthread_stop(cpu_rq(cpu)->migration_thread);
- cpu_rq(cpu)->migration_thread = NULL;
- BUG_ON(cpu_rq(cpu)->nr_running != 0);
break;
#endif
}

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