Re: [PATCH 1/7] perf_counter: fix dynamic irq_period logging

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

On Mon, 2009-05-25 at 10:08 +1000, Paul Mackerras wrote:
> Peter Zijlstra writes:
> 
> > We call perf_adjust_freq() from perf_counter_task_tick() which is is called
> > under the rq->lock causing lock recursion.
> 
> What was the lock recursion?  I see perf_adjust_freq taking ctx->lock,
> but we were careful not to take any rq->lock within a ctx->lock, at
> least in the past.

perf_output_end() can end up calling a wake_up().

perf_output_end()
  perf_output_unlock()
    perf_output_wakeup()
      perf_counter_wakeup()
        wake_up_all();