linux-kernel - Re: [PATCH 5/9] perf/x86: implement cross-HT corruption bug workaround

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Date:	Thu, 5 Jun 2014 15:42:35 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, ak@...ux.intel.com,
	jolsa@...hat.com, zheng.z.yan@...el.com,
	maria.n.dimakopoulou@...il.com
Subject: Re: [PATCH 5/9] perf/x86: implement cross-HT corruption bug
 workaround

On Wed, Jun 04, 2014 at 11:34:14PM +0200, Stephane Eranian wrote:
> +static void intel_commit_scheduling(struct cpu_hw_events *cpuc,
> +				    struct perf_event *event, int cntr)
> +{
> +	struct intel_excl_cntrs *excl_cntrs = cpuc->excl_cntrs;
> +	struct event_constraint *c = event->hw.constraint;
> +	struct intel_excl_states *xlo, *xl;
> +	int tid = cpuc->excl_thread_id;
> +	int o_tid = 1 - tid;
> +	int is_excl;
> +
> +	if (cpuc->is_fake || !c)
> +		return;
> +
> +	is_excl = c->flags & PERF_X86_EVENT_EXCL;
> +
> +	if (!(c->flags & PERF_X86_EVENT_DYNAMIC))
> +		return;
> +
> +	WARN_ON_ONCE(!excl_cntrs);
> +
> +	if (!excl_cntrs)
> +		return;
> +
> +	xl = &excl_cntrs->states[tid];
> +	xlo = &excl_cntrs->states[o_tid];
> +
> +	WARN_ON_ONCE(!spin_is_locked(&excl_cntrs->lock));

Use:
	lockdep_assert_held(&excl_cntrs->lock);

It also checks to see the current context is actually the lock holder,
and it doesn't generate any code when !lockdep.

> +
> +	if (cntr >= 0) {
> +		if (is_excl)
> +			xlo->init_state[cntr] = INTEL_EXCL_EXCLUSIVE;
> +		else
> +			xlo->init_state[cntr] = INTEL_EXCL_SHARED;
> +	}
>  }

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