[PATCH 3/4] MIPS/Perf-events: temporarily connect event to its pmu at event init

[Deng-Cheng Zhu <dczhu@mips.com>]

When arch level event init is called, the event is not yet connected to
the PMU, thereby causing validate_group() to always do dummy work. On MIPS,
this is due to the following lines in validate_event() called by
validate_group():

if (event->pmu != &pmu || event->state <= PERF_EVENT_STATE_OFF)
        return 1;

This patch fixes it.

Signed-off-by: Deng-Cheng Zhu <dczhu@mips.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: David Daney <david.daney@cavium.com>
---
 arch/mips/kernel/perf_event_mipsxx.c |   17 +++++++++++++----
 1 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/arch/mips/kernel/perf_event_mipsxx.c 
b/arch/mips/kernel/perf_event_mipsxx.c
index 1f654ca..c804fdd 100644
--- a/arch/mips/kernel/perf_event_mipsxx.c
+++ b/arch/mips/kernel/perf_event_mipsxx.c
@@ -548,6 +548,7 @@ static int __hw_perf_event_init(struct perf_event *event)
        struct perf_event_attr *attr = &event->attr;
        struct hw_perf_event *hwc = &event->hw;
        const struct mips_perf_event *pev;
+       struct pmu *tmp;
        int err;
 
        /* Returning MIPS event descriptor for generic perf event. */
@@ -611,11 +612,19 @@ static int __hw_perf_event_init(struct perf_event *event)
        }
 
        err = 0;
-       if (event->group_leader != event) {
+
+       /*
+        * we temporarily connect event to its pmu such that
+        * validate_event() in validate_group() can classify
+        * it as a MIPS event by passing (event->pmu == &pmu).
+        */
+       tmp = event->pmu;
+       event->pmu = &pmu;
+
+       if (event->group_leader != event)
                err = validate_group(event);
-               if (err)
-                       return -EINVAL;
-       }
+
+       event->pmu = tmp;
 
        event->destroy = hw_perf_event_destroy;
 
-- 
1.7.1