Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 5d344f58 authored by Christian König's avatar Christian König
Browse files

dma-buf: nuke reservation_object seq number 



The only remaining use for this is to protect against setting a new exclusive
fence while we grab both exclusive and shared. That can also be archived by
looking if the exclusive fence has changed or not after completing the
operation.

v2: switch setting excl fence to rcu_assign_pointer

Signed-off-by: default avatarChristian König <christian.koenig@amd.com>
Reviewed-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/322380/
parent d3c6dd1f

drivers/dma-buf/reservation.c

+5 −19
Original line number Diff line number Diff line
@@ -49,12 +49,6 @@ 
DEFINE_WD_CLASS(reservation_ww_class);

EXPORT_SYMBOL(reservation_ww_class);



struct lock_class_key reservation_seqcount_class;

EXPORT_SYMBOL(reservation_seqcount_class);



const char reservation_seqcount_string[] = "reservation_seqcount";

EXPORT_SYMBOL(reservation_seqcount_string);



/**

 * reservation_object_list_alloc - allocate fence list

 * @shared_max: number of fences we need space for
@@ -103,9 +97,6 @@ static void reservation_object_list_free(struct reservation_object_list *list) 
void reservation_object_init(struct reservation_object *obj)

{

	ww_mutex_init(&obj->lock, &reservation_ww_class);



	__seqcount_init(&obj->seq, reservation_seqcount_string,

			&reservation_seqcount_class);

	RCU_INIT_POINTER(obj->fence, NULL);

	RCU_INIT_POINTER(obj->fence_excl, NULL);

}
@@ -282,12 +273,10 @@ void reservation_object_add_excl_fence(struct reservation_object *obj, 
		dma_fence_get(fence);



	preempt_disable();

	write_seqcount_begin(&obj->seq);

	/* write_seqcount_begin provides the necessary memory barrier */

	RCU_INIT_POINTER(obj->fence_excl, fence);

	rcu_assign_pointer(obj->fence_excl, fence);

	/* pointer update must be visible before we modify the shared_count */

	if (old)

		old->shared_count = 0;

	write_seqcount_end(&obj->seq);

		smp_store_mb(old->shared_count, 0);

	preempt_enable();



	/* inplace update, no shared fences */
@@ -368,11 +357,8 @@ int reservation_object_copy_fences(struct reservation_object *dst, 
	old = reservation_object_get_excl(dst);



	preempt_disable();

	write_seqcount_begin(&dst->seq);

	/* write_seqcount_begin provides the necessary memory barrier */

	RCU_INIT_POINTER(dst->fence_excl, new);

	RCU_INIT_POINTER(dst->fence, dst_list);

	write_seqcount_end(&dst->seq);

	rcu_assign_pointer(dst->fence_excl, new);

	rcu_assign_pointer(dst->fence, dst_list);

	preempt_enable();



	reservation_object_list_free(src_list);

include/linux/reservation.h

+2 −7
Original line number Diff line number Diff line
@@ -46,8 +46,6 @@ 
#include <linux/rcupdate.h>



extern struct ww_class reservation_ww_class;

extern struct lock_class_key reservation_seqcount_class;

extern const char reservation_seqcount_string[];



/**

 * struct reservation_object_list - a list of shared fences
@@ -71,7 +69,6 @@ struct reservation_object_list { 
 */

struct reservation_object {

	struct ww_mutex lock;

	seqcount_t seq;



	struct dma_fence __rcu *fence_excl;

	struct reservation_object_list __rcu *fence;
@@ -130,14 +127,12 @@ reservation_object_fences(struct reservation_object *obj, 
			  struct reservation_object_list **list,

			  u32 *shared_count)

{

	unsigned int seq;



	do {

		seq = read_seqcount_begin(&obj->seq);

		*excl = rcu_dereference(obj->fence_excl);

		*list = rcu_dereference(obj->fence);

		*shared_count = *list ? (*list)->shared_count : 0;

	} while (read_seqcount_retry(&obj->seq, seq));

		smp_rmb(); /* See reservation_object_add_excl_fence */

	} while (rcu_access_pointer(obj->fence_excl) != *excl);

}



/**