perfcounters: enable lowlevel pmc code to schedule counters

Allow lowlevel ->enable() op to return an error if a counter can not be
added. This can be used to handle counter constraints.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 5 insertions, 1 deletions

diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c
index b67557121425..74090a393a7c 100644
--- a/arch/x86/kernel/cpu/perf_counter.c
+++ b/arch/x86/kernel/cpu/perf_counter.c
@@ -244,7 +244,7 @@ static int fixed_mode_idx(struct hw_perf_counter *hwc)
 /*
  * Find a PMC slot for the freshly enabled / scheduled in counter:
  */
-static void pmc_generic_enable(struct perf_counter *counter)
+static int pmc_generic_enable(struct perf_counter *counter)
 {
         struct cpu_hw_counters *cpuc = &__get_cpu_var(cpu_hw_counters);
         struct hw_perf_counter *hwc = &counter->hw;
@@ -253,6 +253,8 @@ static void pmc_generic_enable(struct perf_counter *counter)
         /* Try to get the previous counter again */
         if (test_and_set_bit(idx, cpuc->used)) {
                 idx = find_first_zero_bit(cpuc->used, nr_counters_generic);
+                if (idx == nr_counters_generic)
+                        return -EAGAIN;
                 set_bit(idx, cpuc->used);
                 hwc->idx = idx;
         }
@@ -265,6 +267,8 @@ static void pmc_generic_enable(struct perf_counter *counter)
 
         __hw_perf_counter_set_period(counter, hwc, idx);
         __pmc_generic_enable(counter, hwc, idx);
+
+        return 0;
 }
 
 void perf_counter_print_debug(void)