linux-kernel - Re: [PATCH] perf/x86/uncore: Allow single pmu/box within events group

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Date:   Fri, 18 Nov 2016 13:53:54 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     "Liang, Kan" <kan.liang@...el.com>,
        Andi Kleen <andi@...stfloor.org>,
        Vince Weaver <vince@...ter.net>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] perf/x86/uncore: Allow single pmu/box within events group

On Fri, Nov 18, 2016 at 01:33:25PM +0100, Jiri Olsa wrote:
> On Fri, Nov 18, 2016 at 12:28:50PM +0100, Peter Zijlstra wrote:
> > On Fri, Nov 18, 2016 at 01:15:28AM +0100, Jiri Olsa wrote:
> > > Current uncore_validate_group code expects all events within
> > > the group to have same pmu.
> > > 
> > > This leads to constraint code using wrong boxes which leads
> > > in my case to touching uninitialized spinlocks, but could
> > > be probably worse.. depends on type and box details.
> > > 
> > > I get lockdep warning below for following perf stat:
> > >   # perf stat -vv -e '{uncore_cbox_0/config=0x0334/,uncore_qpi_0/event=1/}' -a sleep 1
> > 
> > Hurm, we shouldn't be allowing that in the first place I think.
> > 
> > 
> > Let me stare at the generic group code, the intent was to only allow
> > software events to mix with hw events, nothing else.
> 
> yep, that's what's happening now.. but after the event_init callback

Ah yes indeed. Its the is_uncore_event() test in uncore_collect_event()
that's too lenient, that allows us to mix events from various uncore
boxes.

Would something like so fix things too? Because that is the point of
is_uncore_event() in collect(), to only collect events for _that_ pmu.

---
 arch/x86/events/intel/uncore.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
index efca2685d876..7b1b34576886 100644
--- a/arch/x86/events/intel/uncore.c
+++ b/arch/x86/events/intel/uncore.c
@@ -319,9 +319,9 @@ static struct intel_uncore_box *uncore_alloc_box(struct intel_uncore_type *type,
  */
 static int uncore_pmu_event_init(struct perf_event *event);
 
-static bool is_uncore_event(struct perf_event *event)
+static bool is_box_event(struct intel_uncore_box *box, struct perf_event *event)
 {
-	return event->pmu->event_init == uncore_pmu_event_init;
+	return box->pmu == event->pmu;
 }
 
 static int
@@ -340,7 +340,7 @@ uncore_collect_events(struct intel_uncore_box *box, struct perf_event *leader,
 
 	n = box->n_events;
 
-	if (is_uncore_event(leader)) {
+	if (is_box_event(box, leader)) {
 		box->event_list[n] = leader;
 		n++;
 	}
@@ -349,7 +349,7 @@ uncore_collect_events(struct intel_uncore_box *box, struct perf_event *leader,
 		return n;
 
 	list_for_each_entry(event, &leader->sibling_list, group_entry) {
-		if (!is_uncore_event(event) ||
+		if (!is_box_event(box, event) ||
 		    event->state <= PERF_EVENT_STATE_OFF)
 			continue;