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SubjectRe: [RFC PATCH V2 2/7] perf: Init/fini PMU specific data
On Fri, Jan 03, 2020 at 11:39:19AM -0800, kan.liang@linux.intel.com wrote:
> From: Kan Liang <kan.liang@linux.intel.com>
>
> The PMU specific data for the monitored tasks only be allocated during
> LBR call stack monitoring.
>
> When a LBR call stack event is accounted, the perf_ctx_data for related
> tasks will be allocated/initialized by init_perf_ctx_data().
> When a LBR call stack event is unaccounted, the perf_ctx_data for
> related tasks will be detached/freed by fini_task_ctx_data().

I hate that 'fini' name. We don't use that anywhere else.

> + raw_spin_lock_irqsave(&task_data_sys_wide_events_lock, flags);
> +
> + /*
> + * Allocate perf_ctx_data for all existing threads with the first
> + * system-wide event.
> + * The perf_ctx_data for new threads will be allocated in
> + * perf_event_fork().
> + */
> + if (atomic_inc_return(&nr_task_data_sys_wide_events) > 1)
> + goto unlock;
> +
> + rcu_read_lock();
> + for_each_process_thread(g, p) {
> + mutex_lock(&p->perf_event_mutex);
> + if (p->perf_ctx_data) {
> + /*
> + * The perf_ctx_data for this thread may has been
> + * allocated by per-task event.
> + * Only update refcount for the case.
> + */
> + refcount_inc(&p->perf_ctx_data->refcount);
> + mutex_unlock(&p->perf_event_mutex);
> + continue;
> + }
> +
> + if (pos < num_thread) {
> + refcount_set(&data[pos]->refcount, 1);
> + rcu_assign_pointer(p->perf_ctx_data, data[pos++]);
> + } else {
> + /*
> + * There may be some new threads created,
> + * when we allocate space.
> + * Track the number in nr_new_tasks.
> + */
> + nr_new_tasks++;
> + }
> + mutex_unlock(&p->perf_event_mutex);
> + }
> + rcu_read_unlock();
> +
> + raw_spin_unlock_irqrestore(&task_data_sys_wide_events_lock, flags);

Still NAK. That's some mightly broken code there.

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