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dma-buf: nuke reservation_object seq number

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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: Christian König <christian.koenig@amd.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/322380/
This commit is contained in:
Christian König
2019-08-05 14:24:55 +02:00
parent d3c6dd1fb3
commit 5d344f58da
2 changed files with 7 additions and 26 deletions
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9
include/linux/reservation.h
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@@ -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);
}
/**