On Fri, Feb 28, 2014 at 03:47:16PM -0500, Steven Rostedt wrote: > > > I'll try your patch momentarily, first I had some other changes I started > > > running before I left work (for some reason it recompiled the whole > > > kernel). > > > > > > 8: function: perf_output_begin > > > 8: bprint: perf_output_begin: VMW: event type 2 config 2a > > > st: 2c3e > > > 8: bputs: perf_output_begin: VMW: before rcu_dereference > > > 9: function: __do_page_fault > > > 9: function: down_read_trylock > > > 9: function: _cond_resched > > > 9: function: find_vma > > > > > > so it looks like the fault happens > > > > > > rcu_read_lock(); > > > > > > 116 /* > > > 117 * For inherited events we send all the output towards the > > > parent. > > > 118 */ > > > 119 if (event->parent) > > > 120 event = event->parent; > > > 121 > > > > > > somewhere between here > > > > > > 122 rb = rcu_dereference(event->rb); > > > 123 if (unlikely(!rb)) > > > 124 goto out; > > > > > > and here > > > > > > 125 > > > 126 if (unlikely(!rb->nr_pages)) > > > 127 goto out; > > > > > > although if rcu locks do anything to turn off tracing then this could be > > > suspect. > > > > The most likely suspect is of course event->rb in the rcu_dereference. > > I have to defer to Steven on how rcu_read_lock() and rcu_read_unlock() > > currently interact with tracing. ;-) > > These are all perf related. You'll need to defer to Peter Zijlstra ;-)
I'm lost.. :/ pretty much all perf objects are RCU freed. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
