linux-kernel - Re: [PATCH v7 06/16] lockdep: Detect and handle hist

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Date:   Tue, 18 Jul 2017 10:25:55 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...nel.org, tglx@...utronix.de, walken@...gle.com,
        boqun.feng@...il.com, kirill@...temov.name,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, willy@...radead.org, npiggin@...il.com,
        kernel-team@....com
Subject: Re: [PATCH v7 06/16] lockdep: Detect and handle hist_lock ring
 buffer overwrite

On Thu, Jul 13, 2017 at 10:14:42AM +0200, Peter Zijlstra wrote:
> +static void __crossrelease_end(unsigned int *stamp)
> +{

[snip]

> +
> +	/*
> +	 * If we rewind past the tail; all of history is lost.
> +	 */
> +	if ((current->xhlock_idx_max - *stamp) < MAX_XHLOCKS_NR)
> +		return;
> +
> +	/*
> +	 * Invalidate the entire history..
> +	 */
> +	for (i = 0; i < MAX_XHLOCKS_NR; i++)
> +		invalidate_xhlock(&xhlock(i));
> +
> +	current->xhlock_idx = 0;
> +	current->xhlock_idx_hard = 0;
> +	current->xhlock_idx_soft = 0;
> +	current->xhlock_idx_hist = 0;
> +	current->xhlock_idx_max = 0;

I don't understand why you introduced this code, yet. Do we need this?

The other of your suggestion looks very good though..

> +}