find_get_context(struct pmu *pmu, struct task_struct *task,
		struct perf_event *event)
{
	struct perf_event_context *ctx, *clone_ctx = NULL;
	struct perf_cpu_context *cpuctx;
	void *task_ctx_data = NULL;
	unsigned long flags;
	int ctxn, err;
	int cpu = event->cpu;

	if (!task) {
		/* Must be root to operate on a CPU event: */
		if (perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN))
			return ERR_PTR(-EACCES);

		/*
		 * We could be clever and allow to attach a event to an
		 * offline CPU and activate it when the CPU comes up, but
		 * that's for later.
		 */
		if (!cpu_online(cpu))
			return ERR_PTR(-ENODEV);

		cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
		ctx = &cpuctx->ctx;
		get_ctx(ctx);
		++ctx->pin_count;

		return ctx;
	}

	err = -EINVAL;
	ctxn = pmu->task_ctx_nr;
	if (ctxn < 0)
		goto errout;

	if (event->attach_state & PERF_ATTACH_TASK_DATA) {
		task_ctx_data = kzalloc(pmu->task_ctx_size, GFP_KERNEL);
		if (!task_ctx_data) {
			err = -ENOMEM;
			goto errout;
		}
	}

retry:
	ctx = perf_lock_task_context(task, ctxn, &flags);
	if (ctx) {
		clone_ctx = unclone_ctx(ctx);
		++ctx->pin_count;

		if (task_ctx_data && !ctx->task_ctx_data) {
			ctx->task_ctx_data = task_ctx_data;
			task_ctx_data = NULL;
		}
		raw_spin_unlock_irqrestore(&ctx->lock, flags);

		if (clone_ctx)
			put_ctx(clone_ctx);
	} else {
		ctx = alloc_perf_context(pmu, task);
		err = -ENOMEM;
		if (!ctx)
			goto errout;

		if (task_ctx_data) {
			ctx->task_ctx_data = task_ctx_data;
			task_ctx_data = NULL;
		}

		err = 0;
		mutex_lock(&task->perf_event_mutex);
		/*
		 * If it has already passed perf_event_exit_task().
		 * we must see PF_EXITING, it takes this mutex too.
		 */
		if (task->flags & PF_EXITING)
			err = -ESRCH;
		else if (task->perf_event_ctxp[ctxn])
			err = -EAGAIN;
		else {
			get_ctx(ctx);
			++ctx->pin_count;
			rcu_assign_pointer(task->perf_event_ctxp[ctxn], ctx);
		}
		mutex_unlock(&task->perf_event_mutex);

		if (unlikely(err)) {
			put_ctx(ctx);

			if (err == -EAGAIN)
				goto retry;
			goto errout;
		}
	}

	kfree(task_ctx_data);
	return ctx;

errout:
	kfree(task_ctx_data);
	return ERR_PTR(err);
}
find_get_context(struct pmu *pmu, struct task_struct *task,
		struct perf_event *event)
{
	struct perf_event_context *ctx, *clone_ctx = NULL;
	struct perf_cpu_context *cpuctx;
	void *task_ctx_data = NULL;
	unsigned long flags;
	int ctxn, err;
	int cpu = event->cpu;

	if (!task) {
		 
		if (perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN))
			return ERR_PTR(-EACCES);

		 
		if (!cpu_online(cpu))
			return ERR_PTR(-ENODEV);

		cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
		ctx = &cpuctx->ctx;
		get_ctx(ctx);
		++ctx->pin_count;

		return ctx;
	}

	err = -EINVAL;
	ctxn = pmu->task_ctx_nr;
	if (ctxn < 0)
		goto errout;

	if (event->attach_state & PERF_ATTACH_TASK_DATA) {
		task_ctx_data = kzalloc(pmu->task_ctx_size, GFP_KERNEL);
		if (!task_ctx_data) {
			err = -ENOMEM;
			goto errout;
		}
	}

retry:
	ctx = perf_lock_task_context(task, ctxn, &flags);
	if (ctx) {
		clone_ctx = unclone_ctx(ctx);
		++ctx->pin_count;

		if (task_ctx_data && !ctx->task_ctx_data) {
			ctx->task_ctx_data = task_ctx_data;
			task_ctx_data = NULL;
		}
		raw_spin_unlock_irqrestore(&ctx->lock, flags);

		if (clone_ctx)
			put_ctx(clone_ctx);
	} else {
		ctx = alloc_perf_context(pmu, task);
		err = -ENOMEM;
		if (!ctx)
			goto errout;

		if (task_ctx_data) {
			ctx->task_ctx_data = task_ctx_data;
			task_ctx_data = NULL;
		}

		err = 0;
		mutex_lock(&task->perf_event_mutex);
		 
		if (task->flags & PF_EXITING)
			err = -ESRCH;
		else if (task->perf_event_ctxp[ctxn])
			err = -EAGAIN;
		else {
			get_ctx(ctx);
			++ctx->pin_count;
			rcu_assign_pointer(task->perf_event_ctxp[ctxn], ctx);
		}
		mutex_unlock(&task->perf_event_mutex);

		if (unlikely(err)) {
			put_ctx(ctx);

			if (err == -EAGAIN)
				goto retry;
			goto errout;
		}
	}

	kfree(task_ctx_data);
	return ctx;

errout:
	kfree(task_ctx_data);
	return ERR_PTR(err);
}