perf/x86/amd: Rework northbridge event constraints handler

Code simplification. No functional changes.

Signed-off-by: Robert Richter <rric@kernel.org>
Signed-off-by: Jacob Shin <jacob.shin@amd.com>
Acked-by: Stephane Eranian <eranian@google.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Robert Richter <rric@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1360171589-6381-2-git-send-email-jacob.shin@amd.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/cpu/perf_event_amd.c b/arch/x86/kernel/cpu/perf_event_amd.c
index c93bc4e..e7963c7 100644 (file)
--- a/arch/x86/kernel/cpu/perf_event_amd.c
+++ b/arch/x86/kernel/cpu/perf_event_amd.c
@@ -256,9 +256,8 @@ amd_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event)
 {
        struct hw_perf_event *hwc = &event->hw;
        struct amd_nb *nb = cpuc->amd_nb;
-       struct perf_event *old = NULL;
-       int max = x86_pmu.num_counters;
-       int i, j, k = -1;
+       struct perf_event *old;
+       int idx, new = -1;
 
        /*
         * if not NB event or no NB, then no constraints
@@ -276,48 +275,33 @@ amd_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event)
         * because of successive calls to x86_schedule_events() from
         * hw_perf_group_sched_in() without hw_perf_enable()
         */
-       for (i = 0; i < max; i++) {
-               /*
-                * keep track of first free slot
-                */
-               if (k == -1 && !nb->owners[i])
-                       k = i;
+       for (idx = 0; idx < x86_pmu.num_counters; idx++) {
+               if (new == -1 || hwc->idx == idx)
+                       /* assign free slot, prefer hwc->idx */
+                       old = cmpxchg(nb->owners + idx, NULL, event);
+               else if (nb->owners[idx] == event)
+                       /* event already present */
+                       old = event;
+               else
+                       continue;
+
+               if (old && old != event)
+                       continue;
+
+               /* reassign to this slot */
+               if (new != -1)
+                       cmpxchg(nb->owners + new, event, NULL);
+               new = idx;
 
                /* already present, reuse */
-               if (nb->owners[i] == event)
-                       goto done;
-       }
-       /*
-        * not present, so grab a new slot
-        * starting either at:
-        */
-       if (hwc->idx != -1) {
-               /* previous assignment */
-               i = hwc->idx;
-       } else if (k != -1) {
-               /* start from free slot found */
-               i = k;
-       } else {
-               /*
-                * event not found, no slot found in
-                * first pass, try again from the
-                * beginning
-                */
-               i = 0;
-       }
-       j = i;
-       do {
-               old = cmpxchg(nb->owners+i, NULL, event);
-               if (!old)
+               if (old == event)
                        break;
-               if (++i == max)
-                       i = 0;
-       } while (i != j);
-done:
-       if (!old)
-               return &nb->event_constraints[i];
-
-       return &emptyconstraint;
+       }
+
+       if (new == -1)
+               return &emptyconstraint;
+
+       return &nb->event_constraints[new];
 }
 
 static struct amd_nb *amd_alloc_nb(int cpu)