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reservation: add suppport for read-only access using rcu

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This adds some extra functions to deal with rcu.

reservation_object_get_fences_rcu() will obtain the list of shared
and exclusive fences without obtaining the ww_mutex.

reservation_object_wait_timeout_rcu() will wait on all fences of the
reservation_object, without obtaining the ww_mutex.

reservation_object_test_signaled_rcu() will test if all fences of the
reservation_object are signaled without using the ww_mutex.

reservation_object_get_excl and reservation_object_get_list require
the reservation object to be held, updating requires
write_seqcount_begin/end. If only the exclusive fence is needed,
rcu_dereference followed by fence_get_rcu can be used, if the shared
fences are needed it's recommended to use the supplied functions.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Acked-by: Daniel Vetter <daniel@ffwll.ch>
Reviewed-By: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Maarten Lankhorst
2014-07-01 12:58:00 +02:00
committed by Greg Kroah-Hartman
parent 04a5faa8cb
commit 3c3b177a93
5 changed files with 400 additions and 54 deletions
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52
include/linux/reservation.h
View File

@@ -42,22 +42,29 @@
#include <linux/ww_mutex.h>
#include <linux/fence.h>
#include <linux/slab.h>
#include <linux/seqlock.h>
#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 {
struct rcu_head rcu;
u32 shared_count, shared_max;
struct fence *shared[];
struct fence __rcu *shared[];
};
struct reservation_object {
struct ww_mutex lock;
seqcount_t seq;
struct fence *fence_excl;
struct reservation_object_list *fence;
struct fence __rcu *fence_excl;
struct reservation_object_list __rcu *fence;
struct reservation_object_list *staged;
};
#define reservation_object_held(obj) lockdep_is_held(&(obj)->lock.base)
#define reservation_object_assert_held(obj) \
lockdep_assert_held(&(obj)->lock.base)
@@ -66,8 +73,9 @@ reservation_object_init(struct reservation_object *obj)
{
ww_mutex_init(&obj->lock, &reservation_ww_class);
obj->fence_excl = NULL;
obj->fence = NULL;
__seqcount_init(&obj->seq, reservation_seqcount_string, &reservation_seqcount_class);
RCU_INIT_POINTER(obj->fence, NULL);
RCU_INIT_POINTER(obj->fence_excl, NULL);
obj->staged = NULL;
}
@@ -76,18 +84,20 @@ reservation_object_fini(struct reservation_object *obj)
{
int i;
struct reservation_object_list *fobj;
struct fence *excl;
/*
* This object should be dead and all references must have
* been released to it.
* been released to it, so no need to be protected with rcu.
*/
if (obj->fence_excl)
fence_put(obj->fence_excl);
excl = rcu_dereference_protected(obj->fence_excl, 1);
if (excl)
fence_put(excl);
fobj = obj->fence;
fobj = rcu_dereference_protected(obj->fence, 1);
if (fobj) {
for (i = 0; i < fobj->shared_count; ++i)
fence_put(fobj->shared[i]);
fence_put(rcu_dereference_protected(fobj->shared[i], 1));
kfree(fobj);
}
@@ -99,17 +109,15 @@ reservation_object_fini(struct reservation_object *obj)
static inline struct reservation_object_list *
reservation_object_get_list(struct reservation_object *obj)
{
reservation_object_assert_held(obj);
return obj->fence;
return rcu_dereference_protected(obj->fence,
reservation_object_held(obj));
}
static inline struct fence *
reservation_object_get_excl(struct reservation_object *obj)
{
reservation_object_assert_held(obj);
return obj->fence_excl;
return rcu_dereference_protected(obj->fence_excl,
reservation_object_held(obj));
}
int reservation_object_reserve_shared(struct reservation_object *obj);
@@ -119,4 +127,16 @@ void reservation_object_add_shared_fence(struct reservation_object *obj,
void reservation_object_add_excl_fence(struct reservation_object *obj,
struct fence *fence);
int reservation_object_get_fences_rcu(struct reservation_object *obj,
struct fence **pfence_excl,
unsigned *pshared_count,
struct fence ***pshared);
long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
bool wait_all, bool intr,
unsigned long timeout);
bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
bool test_all);
#endif /* _LINUX_RESERVATION_H */