perf: Add pmu specific data for perf task context

Introduce a new flag PERF_ATTACH_TASK_DATA for perf event's attach
stata. The flag is set by PMU's event_init() callback, it indicates
that perf event needs PMU specific data.

The PMU specific data are initialized to zeros. Later patches will
use PMU specific data to save LBR stack.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: eranian@google.com
Cc: jolsa@redhat.com
Link: http://lkml.kernel.org/r/1415156173-10035-6-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 36 insertions, 4 deletions

diff --git a/kernel/events/core.c b/kernel/events/core.c
index f563ce767f93..688086bb7144 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -905,6 +905,15 @@ static void get_ctx(struct perf_event_context *ctx)
         WARN_ON(!atomic_inc_not_zero(&ctx->refcount));
 }
 
+static void free_ctx(struct rcu_head *head)
+{
+        struct perf_event_context *ctx;
+
+        ctx = container_of(head, struct perf_event_context, rcu_head);
+        kfree(ctx->task_ctx_data);
+        kfree(ctx);
+}
+
 static void put_ctx(struct perf_event_context *ctx)
 {
         if (atomic_dec_and_test(&ctx->refcount)) {
@@ -912,7 +921,7 @@ static void put_ctx(struct perf_event_context *ctx)
                         put_ctx(ctx->parent_ctx);
                 if (ctx->task)
                         put_task_struct(ctx->task);
-                kfree_rcu(ctx, rcu_head);
+                call_rcu(&ctx->rcu_head, free_ctx);
         }
 }
 
@@ -3309,12 +3318,15 @@ errout:
  * Returns a matching context with refcount and pincount.
  */
 static struct perf_event_context *
-find_get_context(struct pmu *pmu, struct task_struct *task, int cpu)
+find_get_context(struct pmu *pmu, struct task_struct *task,
+                struct perf_event *event)
 {
         struct perf_event_context *ctx, *clone_ctx = NULL;
         struct perf_cpu_context *cpuctx;
+        void *task_ctx_data = NULL;
         unsigned long flags;
         int ctxn, err;
+        int cpu = event->cpu;
 
         if (!task) {
                 /* Must be root to operate on a CPU event: */
@@ -3342,11 +3354,24 @@ find_get_context(struct pmu *pmu, struct task_struct *task, int cpu)
         if (ctxn < 0)
                 goto errout;
 
+        if (event->attach_state & PERF_ATTACH_TASK_DATA) {
+                task_ctx_data = kzalloc(pmu->task_ctx_size, GFP_KERNEL);
+                if (!task_ctx_data) {
+                        err = -ENOMEM;
+                        goto errout;
+                }
+        }
+
 retry:
         ctx = perf_lock_task_context(task, ctxn, &flags);
         if (ctx) {
                 clone_ctx = unclone_ctx(ctx);
                 ++ctx->pin_count;
+
+                if (task_ctx_data && !ctx->task_ctx_data) {
+                        ctx->task_ctx_data = task_ctx_data;
+                        task_ctx_data = NULL;
+                }
                 raw_spin_unlock_irqrestore(&ctx->lock, flags);
 
                 if (clone_ctx)
@@ -3357,6 +3382,11 @@ retry:
                 if (!ctx)
                         goto errout;
 
+                if (task_ctx_data) {
+                        ctx->task_ctx_data = task_ctx_data;
+                        task_ctx_data = NULL;
+                }
+
                 err = 0;
                 mutex_lock(&task->perf_event_mutex);
                 /*
@@ -3383,9 +3413,11 @@ retry:
                 }
         }
 
+        kfree(task_ctx_data);
         return ctx;
 
 errout:
+        kfree(task_ctx_data);
         return ERR_PTR(err);
 }
 
@@ -7559,7 +7591,7 @@ SYSCALL_DEFINE5(perf_event_open,
         /*
          * Get the target context (task or percpu):
          */
-        ctx = find_get_context(pmu, task, event->cpu);
+        ctx = find_get_context(pmu, task, event);
         if (IS_ERR(ctx)) {
                 err = PTR_ERR(ctx);
                 goto err_alloc;
@@ -7765,7 +7797,7 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,
 
         account_event(event);
 
-        ctx = find_get_context(event->pmu, task, cpu);
+        ctx = find_get_context(event->pmu, task, event);
         if (IS_ERR(ctx)) {
                 err = PTR_ERR(ctx);
                 goto err_free;