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>

3 files changed, 51 insertions, 19 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)
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 48f76d2e54c2..53af11d3767b 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -128,7 +128,7 @@ struct perf_counter;
  * struct hw_perf_counter_ops - performance counter hw ops
  */
 struct hw_perf_counter_ops {
-        void (*enable)                  (struct perf_counter *counter);
+        int (*enable)                   (struct perf_counter *counter);
         void (*disable)                 (struct perf_counter *counter);
         void (*read)                    (struct perf_counter *counter);
 };
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index f1110ac1267b..2e73929a6959 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -355,21 +355,25 @@ void perf_counter_task_sched_out(struct task_struct *task, int cpu)
         cpuctx->task_ctx = NULL;
 }
 
-static void
+static int
 counter_sched_in(struct perf_counter *counter,
                  struct perf_cpu_context *cpuctx,
                  struct perf_counter_context *ctx,
                  int cpu)
 {
         if (counter->state == PERF_COUNTER_STATE_OFF)
-                return;
+                return 0;
+
+        if (counter->hw_ops->enable(counter))
+                return -EAGAIN;
 
-        counter->hw_ops->enable(counter);
         counter->state = PERF_COUNTER_STATE_ACTIVE;
         counter->oncpu = cpu;   /* TODO: put 'cpu' into cpuctx->cpu */
 
         cpuctx->active_oncpu++;
         ctx->nr_active++;
+
+        return 0;
 }
 
 static int
@@ -378,20 +382,38 @@ group_sched_in(struct perf_counter *group_counter,
                struct perf_counter_context *ctx,
                int cpu)
 {
-        struct perf_counter *counter;
-        int was_group = 0;
+        struct perf_counter *counter, *partial_group;
+        int ret = 0;
 
-        counter_sched_in(group_counter, cpuctx, ctx, cpu);
+        if (counter_sched_in(group_counter, cpuctx, ctx, cpu))
+                return -EAGAIN;
 
         /*
          * Schedule in siblings as one group (if any):
          */
         list_for_each_entry(counter, &group_counter->sibling_list, list_entry) {
-                counter_sched_in(counter, cpuctx, ctx, cpu);
-                was_group = 1;
+                if (counter_sched_in(counter, cpuctx, ctx, cpu)) {
+                        partial_group = counter;
+                        goto group_error;
+                }
+                ret = -EAGAIN;
         }
 
-        return was_group;
+        return ret;
+
+group_error:
+        /*
+         * Groups can be scheduled in as one unit only, so undo any
+         * partial group before returning:
+         */
+        list_for_each_entry(counter, &group_counter->sibling_list, list_entry) {
+                if (counter == partial_group)
+                        break;
+                counter_sched_out(counter, cpuctx, ctx);
+        }
+        counter_sched_out(group_counter, cpuctx, ctx);
+
+        return -EAGAIN;
 }
 
 /*
@@ -416,9 +438,6 @@ void perf_counter_task_sched_in(struct task_struct *task, int cpu)
 
         spin_lock(&ctx->lock);
         list_for_each_entry(counter, &ctx->counter_list, list_entry) {
-                if (ctx->nr_active == cpuctx->max_pertask)
-                        break;
-
                 /*
                  * Listen to the 'cpu' scheduling filter constraint
                  * of counters:
@@ -856,8 +875,9 @@ static const struct file_operations perf_fops = {
         .poll                   = perf_poll,
 };
 
-static void cpu_clock_perf_counter_enable(struct perf_counter *counter)
+static int cpu_clock_perf_counter_enable(struct perf_counter *counter)
 {
+        return 0;
 }
 
 static void cpu_clock_perf_counter_disable(struct perf_counter *counter)
@@ -913,11 +933,13 @@ static void task_clock_perf_counter_read(struct perf_counter *counter)
         task_clock_perf_counter_update(counter, now);
 }
 
-static void task_clock_perf_counter_enable(struct perf_counter *counter)
+static int task_clock_perf_counter_enable(struct perf_counter *counter)
 {
         u64 now = task_clock_perf_counter_val(counter, 0);
 
         atomic64_set(&counter->hw.prev_count, now);
+
+        return 0;
 }
 
 static void task_clock_perf_counter_disable(struct perf_counter *counter)
@@ -960,12 +982,14 @@ static void page_faults_perf_counter_read(struct perf_counter *counter)
         page_faults_perf_counter_update(counter);
 }
 
-static void page_faults_perf_counter_enable(struct perf_counter *counter)
+static int page_faults_perf_counter_enable(struct perf_counter *counter)
 {
         /*
          * page-faults is a per-task value already,
          * so we dont have to clear it on switch-in.
          */
+
+        return 0;
 }
 
 static void page_faults_perf_counter_disable(struct perf_counter *counter)
@@ -1006,12 +1030,14 @@ static void context_switches_perf_counter_read(struct perf_counter *counter)
         context_switches_perf_counter_update(counter);
 }
 
-static void context_switches_perf_counter_enable(struct perf_counter *counter)
+static int context_switches_perf_counter_enable(struct perf_counter *counter)
 {
         /*
          * ->nvcsw + curr->nivcsw is a per-task value already,
          * so we dont have to clear it on switch-in.
          */
+
+        return 0;
 }
 
 static void context_switches_perf_counter_disable(struct perf_counter *counter)
@@ -1050,12 +1076,14 @@ static void cpu_migrations_perf_counter_read(struct perf_counter *counter)
         cpu_migrations_perf_counter_update(counter);
 }
 
-static void cpu_migrations_perf_counter_enable(struct perf_counter *counter)
+static int cpu_migrations_perf_counter_enable(struct perf_counter *counter)
 {
         /*
          * se.nr_migrations is a per-task value already,
          * so we dont have to clear it on switch-in.
          */
+
+        return 0;
 }
 
 static void cpu_migrations_perf_counter_disable(struct perf_counter *counter)