[PATCH V6 05/17] perf, core: pmu specific data for perf task context

Kan Liang
2014-10-19T22:05:43Z

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>
---
include/linux/perf_event.h | 6 ++++++
kernel/events/core.c | 40 ++++++++++++++++++++++++++++++++++++----
2 files changed, 42 insertions(+), 4 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index c392fd5..159e092 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -264,6 +264,10 @@ struct pmu {
*/
void (*sched_task) (struct perf_event_context *ctx,
bool sched_in);
+ /*
+ * PMU specific data size
+ */
+ size_t task_ctx_size;

};

@@ -300,6 +304,7 @@ 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;
@@ -509,6 +514,7 @@ 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 5971e7d..a7c0d5c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -895,6 +895,15 @@ 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)) {
@@ -902,7 +911,7 @@ 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);
}
}

@@ -3188,12 +3197,15 @@ 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: */
@@ -3221,11 +3233,24 @@ 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)
@@ -3236,6 +3261,11 @@ 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);
/*
@@ -3262,9 +3292,11 @@ retry:
}
}

+ kfree(task_ctx_data);
return ctx;

errout:
+ kfree(task_ctx_data);
return ERR_PTR(err);
}

@@ -7344,7 +7376,7 @@ 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;
@@ -7513,7 +7545,7 @@ 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;
--
1.8.3.2