perf_counter: Push inherit into perf_counter_alloc()

Teach perf_counter_alloc() about inheritance so that we can
optimize the inherit path in the next patch.

Remove the child_counter->atrr.inherit = 1 line because the
only way to get there is if parent_counter->attr.inherit == 1
and we copy the attrs.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 6 insertions, 8 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 7515c7695428..0a45490f4029 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -3568,6 +3568,7 @@ perf_counter_alloc(struct perf_counter_attr *attr,
                    int cpu,
                    struct perf_counter_context *ctx,
                    struct perf_counter *group_leader,
+                   struct perf_counter *parent_counter,
                    gfp_t gfpflags)
 {
         const struct pmu *pmu;
@@ -3603,6 +3604,8 @@ perf_counter_alloc(struct perf_counter_attr *attr,
         counter->ctx            = ctx;
         counter->oncpu          = -1;
 
+        counter->parent         = parent_counter;
+
         counter->ns             = get_pid_ns(current->nsproxy->pid_ns);
         counter->id             = atomic64_inc_return(&perf_counter_id);
 
@@ -3827,7 +3830,7 @@ SYSCALL_DEFINE5(perf_counter_open,
         }
 
         counter = perf_counter_alloc(&attr, cpu, ctx, group_leader,
-                                     GFP_KERNEL);
+                                     NULL, GFP_KERNEL);
         ret = PTR_ERR(counter);
         if (IS_ERR(counter))
                 goto err_put_context;
@@ -3893,7 +3896,8 @@ inherit_counter(struct perf_counter *parent_counter,
 
         child_counter = perf_counter_alloc(&parent_counter->attr,
                                            parent_counter->cpu, child_ctx,
-                                           group_leader, GFP_KERNEL);
+                                           group_leader, parent_counter,
+                                           GFP_KERNEL);
         if (IS_ERR(child_counter))
                 return child_counter;
         get_ctx(child_ctx);
@@ -3916,12 +3920,6 @@ inherit_counter(struct perf_counter *parent_counter,
          */
         add_counter_to_ctx(child_counter, child_ctx);
 
-        child_counter->parent = parent_counter;
-        /*
-         * inherit into child's child as well:
-         */
-        child_counter->attr.inherit = 1;
-
         /*
          * Get a reference to the parent filp - we will fput it
          * when the child counter exits. This is safe to do because