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SubjectRe: [patch 1/5] x86, ftrace, hw-branch-tracer: support hotplug cpus
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On Fri, 2009-01-16 at 11:50 +0100, Markus Metzger wrote:

> static void bts_trace_print_header(struct seq_file *m)
> {
> seq_puts(m,
> @@ -107,18 +173,34 @@
> {
> struct ring_buffer_event *event;
> struct hw_branch_entry *entry;
> - unsigned long irq;
> + unsigned long irq1, irq2;
> + int cpu;
> +
> + if (unlikely(!tr))
> + return;
> +
> + if (unlikely(!trace_hw_branches_enabled))
> + return;
> +
> + local_irq_save(irq1);
> + cpu = raw_smp_processor_id();
> + if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
> + goto out;
>
> - event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry), &irq);
> + event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry), &irq2);
> if (!event)
> return;

You need a goto out here, otherwise you leave with interrupts disabled.

Doing 'echo 0 > /debug/tracing/tracing_on' will guarantee that you hit
this return.

-- Steve

> entry = ring_buffer_event_data(event);
> tracing_generic_entry_update(&entry->ent, 0, from);
> entry->ent.type = TRACE_HW_BRANCHES;
> - entry->ent.cpu = smp_processor_id();
> + entry->ent.cpu = cpu;
> entry->from = from;
> entry->to = to;
> - ring_buffer_unlock_commit(tr->buffer, event, irq);
> + ring_buffer_unlock_commit(tr->buffer, event, irq2);
> +
> + out:
> + atomic_dec(&tr->data[cpu]->disabled);
> + local_irq_restore(irq1);
> }
>
> static void trace_bts_at(struct trace_array *tr,
> @@ -142,6 +224,11 @@
> }
> }
>
> +



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