Re: [Linaro-mm-sig] [PATCH 6/7] reservation: cross-device reservation support

[Francesco Lavra <francescolavra.fl@gmail.com>]

On 01/15/2013 01:34 PM, Maarten Lankhorst wrote:
> This adds support for a generic reservations framework that can be
> hooked up to ttm and dma-buf and allows easy sharing of reservations
> across devices.
> 
> The idea is that a dma-buf and ttm object both will get a pointer
> to a struct reservation_object, which has to be reserved before
> anything is done with the contents of the dma-buf.
> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
> ---
>  Documentation/DocBook/device-drivers.tmpl |   2 +
>  drivers/base/Makefile                     |   2 +-
>  drivers/base/reservation.c                | 251 ++++++++++++++++++++++++++++++
>  include/linux/reservation.h               | 182 ++++++++++++++++++++++
>  4 files changed, 436 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/base/reservation.c
>  create mode 100644 include/linux/reservation.h
[...]
> diff --git a/include/linux/reservation.h b/include/linux/reservation.h
> new file mode 100644
> index 0000000..fc2349d
> --- /dev/null
> +++ b/include/linux/reservation.h
> @@ -0,0 +1,182 @@
> +/*
> + * Header file for reservations for dma-buf and ttm
> + *
> + * Copyright(C) 2011 Linaro Limited. All rights reserved.
> + * Copyright (C) 2012 Canonical Ltd
> + * Copyright (C) 2012 Texas Instruments
> + *
> + * Authors:
> + * Rob Clark <rob.clark@linaro.org>
> + * Maarten Lankhorst <maarten.lankhorst@canonical.com>
> + * Thomas Hellstrom <thellstrom-at-vmware-dot-com>
> + *
> + * Based on bo.c which bears the following copyright notice,
> + * but is dual licensed:
> + *
> + * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
> + * All Rights Reserved.
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the
> + * "Software"), to deal in the Software without restriction, including
> + * without limitation the rights to use, copy, modify, merge, publish,
> + * distribute, sub license, and/or sell copies of the Software, and to
> + * permit persons to whom the Software is furnished to do so, subject to
> + * the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the
> + * next paragraph) shall be included in all copies or substantial portions
> + * of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
> + * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
> + * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
> + * USE OR OTHER DEALINGS IN THE SOFTWARE.
> + */
> +#ifndef _LINUX_RESERVATION_H
> +#define _LINUX_RESERVATION_H
> +
> +#include <linux/spinlock.h>
> +#include <linux/mutex.h>
> +#include <linux/fence.h>
> +
> +#define BUF_MAX_SHARED_FENCE 8
> +
> +struct fence;
> +
> +extern atomic_long_t reservation_counter;
> +extern const char reservation_object_name[];
> +extern struct lock_class_key reservation_object_class;
> +extern const char reservation_ticket_name[];
> +extern struct lock_class_key reservation_ticket_class;
> +
> +struct reservation_object {
> +	struct ticket_mutex lock;
> +
> +	u32 fence_shared_count;
> +	struct fence *fence_excl;
> +	struct fence *fence_shared[BUF_MAX_SHARED_FENCE];
> +};
> +
> +struct reservation_ticket {
> +	unsigned long seqno;
> +#ifdef CONFIG_DEBUG_LOCK_ALLOC
> +	struct lockdep_map dep_map;
> +#endif
> +};
> +
> +/**
> + * struct reservation_entry - reservation structure for a
> + * reservation_object
> + * @head:	list entry
> + * @obj_shared:	pointer to a reservation_object to reserve
> + *
> + * Bit 0 of obj_shared is set to bool shared, as such pointer has to be
> + * converted back, which can be done with reservation_entry_get.
> + */
> +struct reservation_entry {
> +	struct list_head head;
> +	unsigned long obj_shared;
> +};
> +
> +
> +static inline void
> +reservation_object_init(struct reservation_object *obj)
> +{
> +	obj->fence_shared_count = 0;
> +	obj->fence_excl = NULL;
> +
> +	__ticket_mutex_init(&obj->lock, reservation_object_name,
> +			    &reservation_object_class);
> +}
> +
> +static inline void
> +reservation_object_fini(struct reservation_object *obj)
> +{
> +	int i;
> +
> +	if (obj->fence_excl)
> +		fence_put(obj->fence_excl);
> +	for (i = 0; i < obj->fence_shared_count; ++i)
> +		fence_put(obj->fence_shared[i]);
> +
> +	mutex_destroy(&obj->lock.base);
> +}
> +
> +static inline void
> +reservation_ticket_init(struct reservation_ticket *t)
> +{
> +#ifdef CONFIG_DEBUG_LOCK_ALLOC
> +	/*
> +	 * Make sure we are not reinitializing a held ticket:
> +	 */
> +
> +	debug_check_no_locks_freed((void *)t, sizeof(*t));
> +	lockdep_init_map(&t->dep_map, reservation_ticket_name,
> +			 &reservation_ticket_class, 0);
> +#endif
> +	mutex_acquire(&t->dep_map, 0, 0, _THIS_IP_);

If CONFIG_DEBUG_LOCK_ALLOC is not defined, t->dep_map is not there.

> +	do {
> +		t->seqno = atomic_long_inc_return(&reservation_counter);
> +	} while (unlikely(!t->seqno));
> +}

--
Francesco