[patch 07/18] sched: add notifier for cross-cpu migrations

[Marcelo Tosatti <mtosatti@redhat.com>]

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[-- Type: text/plain, Size: 1732 bytes --]

Originally from Jeremy Fitzhardinge.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Index: vsyscall/include/linux/sched.h
===================================================================
--- vsyscall.orig/include/linux/sched.h
+++ vsyscall/include/linux/sched.h
@@ -107,6 +107,14 @@ extern unsigned long this_cpu_load(void)
 extern void calc_global_load(unsigned long ticks);
 extern void update_cpu_load_nohz(void);
 
+/* Notifier for when a task gets migrated to a new CPU */
+struct task_migration_notifier {
+	struct task_struct *task;
+	int from_cpu;
+	int to_cpu;
+};
+extern void register_task_migration_notifier(struct notifier_block *n);
+
 extern unsigned long get_parent_ip(unsigned long addr);
 
 struct seq_file;
Index: vsyscall/kernel/sched/core.c
===================================================================
--- vsyscall.orig/kernel/sched/core.c
+++ vsyscall/kernel/sched/core.c
@@ -922,6 +922,13 @@ void check_preempt_curr(struct rq *rq, s
 		rq->skip_clock_update = 1;
 }
 
+static ATOMIC_NOTIFIER_HEAD(task_migration_notifier);
+
+void register_task_migration_notifier(struct notifier_block *n)
+{
+	atomic_notifier_chain_register(&task_migration_notifier, n);
+}
+
 #ifdef CONFIG_SMP
 void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
 {
@@ -952,8 +959,16 @@ void set_task_cpu(struct task_struct *p,
 	trace_sched_migrate_task(p, new_cpu);
 
 	if (task_cpu(p) != new_cpu) {
+		struct task_migration_notifier tmn;
+
 		p->se.nr_migrations++;
 		perf_sw_event(PERF_COUNT_SW_CPU_MIGRATIONS, 1, NULL, 0);
+
+		tmn.task = p;
+		tmn.from_cpu = task_cpu(p);
+		tmn.to_cpu = new_cpu;
+
+		atomic_notifier_call_chain(&task_migration_notifier, 0, &tmn);
 	}
 
 	__set_task_cpu(p, new_cpu);