diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index 25b1cc07d496..d6b078e9fa28 100644
--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -95,7 +95,6 @@ unsigned __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src,
struct pvclock_vsyscall_time_info {
struct pvclock_vcpu_time_info pvti;
- u32 migrate_count;
} __attribute__((__aligned__(SMP_CACHE_BYTES)));
#define PVTI_SIZE sizeof(struct pvclock_vsyscall_time_info)
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
index e5ecd20e72dd..2f355d229a58 100644
--- a/arch/x86/kernel/pvclock.c
+++ b/arch/x86/kernel/pvclock.c
@@ -141,46 +141,7 @@ void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
}
-static struct pvclock_vsyscall_time_info *pvclock_vdso_info;
-
-static struct pvclock_vsyscall_time_info *
-pvclock_get_vsyscall_user_time_info(int cpu)
-{
- if (!pvclock_vdso_info) {
- BUG();
- return NULL;
- }
-
- return &pvclock_vdso_info[cpu];
-}
-
-struct pvclock_vcpu_time_info *pvclock_get_vsyscall_time_info(int cpu)
-{
- return &pvclock_get_vsyscall_user_time_info(cpu)->pvti;
-}
-
#ifdef CONFIG_X86_64
-static int pvclock_task_migrate(struct notifier_block *nb, unsigned long l,
- void *v)
-{
- struct task_migration_notifier *mn = v;
- struct pvclock_vsyscall_time_info *pvti;
-
- pvti = pvclock_get_vsyscall_user_time_info(mn->from_cpu);
-
- /* this is NULL when pvclock vsyscall is not initialized */
- if (unlikely(pvti == NULL))
- return NOTIFY_DONE;
-
- pvti->migrate_count++;
-
- return NOTIFY_DONE;
-}
-
-static struct notifier_block pvclock_migrate = {
- .notifier_call = pvclock_task_migrate,
-};
-
/*
* Initialize the generic pvclock vsyscall state. This will allocate
* a/some page(s) for the per-vcpu pvclock information, set up a
@@ -194,17 +155,12 @@ int __init pvclock_init_vsyscall(struct pvclock_vsyscall_time_info *i,
WARN_ON (size != PVCLOCK_VSYSCALL_NR_PAGES*PAGE_SIZE);
- pvclock_vdso_info = i;
-
for (idx = 0; idx <= (PVCLOCK_FIXMAP_END-PVCLOCK_FIXMAP_BEGIN); idx++) {
__set_fixmap(PVCLOCK_FIXMAP_BEGIN + idx,
__pa(i) + (idx*PAGE_SIZE),
PAGE_KERNEL_VVAR);
}
-
- register_task_migration_notifier(&pvclock_migrate);
-
return 0;
}
#endif
diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c
index 40d2473836c9..9793322751e0 100644
--- a/arch/x86/vdso/vclock_gettime.c
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -82,15 +82,18 @@ static notrace cycle_t vread_pvclock(int *mode)
cycle_t ret;
u64 last;
u32 version;
- u32 migrate_count;
u8 flags;
unsigned cpu, cpu1;
/*
- * When looping to get a consistent (time-info, tsc) pair, we
- * also need to deal with the possibility we can switch vcpus,
- * so make sure we always re-fetch time-info for the current vcpu.
+ * Note: hypervisor must guarantee that:
+ * 1. cpu ID number maps 1:1 to per-CPU pvclock time info.
+ * 2. that per-CPU pvclock time info is updated if the
+ * underlying CPU changes.
+ * 3. that version is increased whenever underlying CPU
+ * changes.
+ *
*/
do {
cpu = __getcpu() & VGETCPU_CPU_MASK;
@@ -99,27 +102,20 @@ static notrace cycle_t vread_pvclock(int *mode)
* __getcpu() calls (Gleb).
*/
- /* Make sure migrate_count will change if we leave the VCPU. */
- do {
- pvti = get_pvti(cpu);
- migrate_count = pvti->migrate_count;
-
- cpu1 = cpu;
- cpu = __getcpu() & VGETCPU_CPU_MASK;
- } while (unlikely(cpu != cpu1));
+ pvti = get_pvti(cpu);
version = __pvclock_read_cycles(&pvti->pvti, &ret, &flags);
/*
* Test we're still on the cpu as well as the version.
- * - We must read TSC of pvti's VCPU.
- * - KVM doesn't follow the versioning protocol, so data could
- * change before version if we left the VCPU.
+ * We could have been migrated just after the first
+ * vgetcpu but before fetching the version, so we
+ * wouldn't notice a version change.
*/
- smp_rmb();
- } while (unlikely((pvti->pvti.version & 1) ||
- pvti->pvti.version != version ||
- pvti->migrate_count != migrate_count));
+ cpu1 = __getcpu() & VGETCPU_CPU_MASK;
+ } while (unlikely(cpu != cpu1 ||
+ (pvti->pvti.version & 1) ||
+ pvti->pvti.version != version));
if (unlikely(!(flags & PVCLOCK_TSC_STABLE_BIT)))
*mode = VCLOCK_NONE;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8222ae40ecb0..26a2e6122734 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -175,14 +175,6 @@ extern void get_iowait_load(unsigned long *nr_waiters, unsigned long *load);
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);
extern void dump_cpu_task(int cpu);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f9123a82cbb6..fe22f7510bce 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1016,13 +1016,6 @@ void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
rq_clock_skip_update(rq, true);
}
-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)
{
@@ -1053,18 +1046,10 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
trace_sched_migrate_task(p, new_cpu);
if (task_cpu(p) != new_cpu) {
- struct task_migration_notifier tmn;
-
if (p->sched_class->migrate_task_rq)
p->sched_class->migrate_task_rq(p, new_cpu);
p->se.nr_migrations++;
perf_sw_event_sched(PERF_COUNT_SW_CPU_MIGRATIONS, 1, 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);