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>

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index c7007a5..270cd01 100644 (file)
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -271,6 +271,10 @@ struct pmu {
         */
        void (*sched_task)              (struct perf_event_context *ctx,
                                        bool sched_in);
+       /*
+        * PMU specific data size
+        */
+       size_t                          task_ctx_size;
 
 };
 
@@ -307,6 +311,7 @@ struct swevent_hlist {
 #define PERF_ATTACH_CONTEXT    0x01
 #define PERF_ATTACH_GROUP      0x02
 #define PERF_ATTACH_TASK       0x04
+#define PERF_ATTACH_TASK_DATA  0x08
 
 struct perf_cgroup;
 struct ring_buffer;
@@ -511,6 +516,7 @@ struct perf_event_context {
        u64                             generation;
        int                             pin_count;
        int                             nr_cgroups;      /* cgroup evts */
+       void                            *task_ctx_data; /* pmu specific data */
        struct rcu_head                 rcu_head;
 
        struct delayed_work             orphans_remove;

diff --git a/kernel/events/core.c b/kernel/events/core.c
index f563ce7..688086b 100644 (file)
--- 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;