Re: [PATCH 3/6] drm/atomic: Don't overrun the connector array when hotplugging

From: Thierry Reding <thierry.reding@gmail.com>
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Daniel Vetter <daniel.vetter@intel.com>,
	Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
	DRI Development <dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH 3/6] drm/atomic: Don't overrun the connector array when hotplugging
Date: Thu, 20 Nov 2014 09:53:34 +0100	[thread overview]
Message-ID: <20141120085328.GA23043@ulmo> (raw)
In-Reply-To: <1416418691-24747-3-git-send-email-daniel.vetter@ffwll.ch>

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On Wed, Nov 19, 2014 at 06:38:08PM +0100, Daniel Vetter wrote:
[...]
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
[...]
> @@ -304,6 +306,21 @@ drm_atomic_get_connector_state(struct drm_atomic_state *state,
>  
>  	index = drm_connector_index(connector);
>  
> +	/*
> +	 * Construction of atomic state updates can race with a connector
> +	 * hot-add which might overflow. In this case flip the table and just
> +	 * restart the entire ioctl - no one is fast enough to livelock a cpu
> +	 * with physical hotplug events anyway.
> +	 *
> +	 * Note that we only grab the indexes once we have the right lock to
> +	 * prevent hotplug/unplugging of connectors. So removal is no problem,
> +	 * at most the array is a bit too large.
> +	 */
> +	if (index >= state->num_connector) {
> +		DRM_DEBUG_KMS("Hot-added connector would overflow state array, restarting\n");
> +		return -EAGAIN;

This function returns a pointer, so this needs to be ERR_PTR(-EAGAIN).

Thierry

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