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SubjectRe: [tip:perf/core] perf: Add pmu specific data for perf task context
On Wed, Feb 18, 2015 at 09:15:06AM -0800, tip-bot for Yan, Zheng wrote:
> +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);
> }


diff --git a/kernel/events/core.c b/kernel/events/core.c
index 36babfd..97aa610 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3508,11 +3515,6 @@ 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);
/*
@@ -3526,6 +3528,10 @@ retry:
else {
get_ctx(ctx);
++ctx->pin_count;
+ if (task_ctx_data) {
+ ctx->task_ctx_data = task_ctx_data;
+ task_ctx_data = NULL;
+ }
rcu_assign_pointer(task->perf_event_ctxp[ctxn], ctx);
}
mutex_unlock(&task->perf_event_mutex);

Does that make sense? No point in setting task_ctx_data if we're going
to free the ctx and try again.


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