Messages in this thread | | | Date | Mon, 25 Apr 2016 15:10:13 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v1 4/5] perf: Introduce address range filtering |
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On Fri, Apr 22, 2016 at 07:19:11PM +0300, Alexander Shishkin wrote: > +static int perf_event_restart(struct perf_event *event) > +{ > + struct stop_event_data sd = { > + .event = event, > + .restart = 1, > + }; > + int ret = 0; > + > + do { > + if (READ_ONCE(event->state) != PERF_EVENT_STATE_ACTIVE) > + return 0; > + > + /* matches smp_wmb() in event_sched_in() */ > + smp_rmb(); > + > + ret = cpu_function_call(READ_ONCE(event->oncpu), > + __perf_event_stop, &sd); > + } while (ret == -EAGAIN); > + > + return ret; > +}
A few concerns with this;
- if I understand things right; this will loose a bit of trace when people tickle the ioctl(), right? This might want a note of sorts,
- you need to handle event->oncpu == -1,
- can we race with an actual stop, and accidentally re-enable the thing? If not, this might be a good place for a comment explaining how.
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