Re: [PATCH] perf_events: fix cgrp stale pointer inupdate_cgrp_time_from_cpuctx()

[Ingo Molnar]

* Stephane Eranian <eranian@xxxxxxxxxx> wrote:

> -	if (is_cgroup_event(event))
> +	if (is_cgroup_event(event)) {
>  		ctx->nr_cgroups--;
> +		cpuctx = __get_cpu_context(ctx);
> +		/*
> +		 * if there are no more cgroup events
> +		 * then clear cgrp to avoid stale pointer
> +		 * in update_cgrp_time_from_cpuctx()
> +		 */
> +		if (!ctx->nr_cgroups)
> +			cpuctx->cgrp = NULL;
> +	}

The ->cgrp pointer does not exist on !CGROUPS kernels. I suspect the cleanest 
approach would be to make those two cgrp fields available unconditionally in 
struct perf_event.

Thanks,

	Ingo
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