[PATCH WW 04/13] drm/ttm: convert to the reservation api
Maarten Lankhorst
m.b.lankhorst at gmail.com
Thu Jun 27 04:48:19 PDT 2013
Now that the code is compatible in semantics, flip the switch.
Use ww_mutex instead of the homegrown implementation.
ww_mutex uses -EDEADLK to signal that the caller has to back off,
and -EALREADY to indicate this buffer is already held by the caller.
ttm used -EAGAIN and -EDEADLK for those, respectively. So some changes
were needed to handle this correctly.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst at canonical.com>
---
drivers/gpu/drm/nouveau/nouveau_gem.c | 2 +-
drivers/gpu/drm/qxl/qxl_object.h | 5 -
drivers/gpu/drm/ttm/ttm_bo.c | 190 +++++++++------------------------
drivers/gpu/drm/ttm/ttm_bo_util.c | 6 +-
drivers/gpu/drm/ttm/ttm_execbuf_util.c | 43 +++-----
include/drm/ttm/ttm_bo_api.h | 25 ++---
include/drm/ttm/ttm_execbuf_util.h | 1 -
7 files changed, 79 insertions(+), 193 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c b/drivers/gpu/drm/nouveau/nouveau_gem.c
index e35d468..2b2077d 100644
--- a/drivers/gpu/drm/nouveau/nouveau_gem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
@@ -368,7 +368,7 @@ retry:
ret = ttm_bo_reserve(&nvbo->bo, true, false, true, &op->ticket);
if (ret) {
validate_fini_no_ticket(op, NULL);
- if (unlikely(ret == -EAGAIN)) {
+ if (unlikely(ret == -EDEADLK)) {
ret = ttm_bo_reserve_slowpath(&nvbo->bo, true,
&op->ticket);
if (!ret)
diff --git a/drivers/gpu/drm/qxl/qxl_object.h b/drivers/gpu/drm/qxl/qxl_object.h
index b4fd89f..ee7ad79 100644
--- a/drivers/gpu/drm/qxl/qxl_object.h
+++ b/drivers/gpu/drm/qxl/qxl_object.h
@@ -57,11 +57,6 @@ static inline unsigned long qxl_bo_size(struct qxl_bo *bo)
return bo->tbo.num_pages << PAGE_SHIFT;
}
-static inline bool qxl_bo_is_reserved(struct qxl_bo *bo)
-{
- return !!atomic_read(&bo->tbo.reserved);
-}
-
static inline u64 qxl_bo_mmap_offset(struct qxl_bo *bo)
{
return bo->tbo.addr_space_offset;
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index b912375..5f9fe80 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -150,6 +150,9 @@ static void ttm_bo_release_list(struct kref *list_kref)
if (bo->ttm)
ttm_tt_destroy(bo->ttm);
atomic_dec(&bo->glob->bo_count);
+ if (bo->resv == &bo->ttm_resv)
+ reservation_object_fini(&bo->ttm_resv);
+
if (bo->destroy)
bo->destroy(bo);
else {
@@ -158,18 +161,6 @@ static void ttm_bo_release_list(struct kref *list_kref)
ttm_mem_global_free(bdev->glob->mem_glob, acc_size);
}
-static int ttm_bo_wait_unreserved(struct ttm_buffer_object *bo,
- bool interruptible)
-{
- if (interruptible) {
- return wait_event_interruptible(bo->event_queue,
- !ttm_bo_is_reserved(bo));
- } else {
- wait_event(bo->event_queue, !ttm_bo_is_reserved(bo));
- return 0;
- }
-}
-
void ttm_bo_add_to_lru(struct ttm_buffer_object *bo)
{
struct ttm_bo_device *bdev = bo->bdev;
@@ -218,65 +209,27 @@ int ttm_bo_reserve_nolru(struct ttm_buffer_object *bo,
bool no_wait, bool use_ticket,
struct ww_acquire_ctx *ticket)
{
- int ret;
+ int ret = 0;
- while (unlikely(atomic_xchg(&bo->reserved, 1) != 0)) {
- /**
- * Deadlock avoidance for multi-bo reserving.
- */
- if (use_ticket && bo->seq_valid) {
- /**
- * We've already reserved this one.
- */
- if (unlikely(ticket->stamp == bo->val_seq))
- return -EDEADLK;
- /**
- * Already reserved by a thread that will not back
- * off for us. We need to back off.
- */
- if (unlikely(ticket->stamp - bo->val_seq <= LONG_MAX))
- return -EAGAIN;
- }
+ if (no_wait) {
+ bool success;
- if (no_wait)
+ /* not valid any more, fix your locking! */
+ if (WARN_ON(ticket))
return -EBUSY;
- ret = ttm_bo_wait_unreserved(bo, interruptible);
-
- if (unlikely(ret))
- return ret;
- }
-
- if (use_ticket) {
- bool wake_up = false;
-
- /**
- * Wake up waiters that may need to recheck for deadlock,
- * if we decreased the sequence number.
- */
- if (unlikely((bo->val_seq - ticket->stamp <= LONG_MAX)
- || !bo->seq_valid))
- wake_up = true;
-
- /*
- * In the worst case with memory ordering these values can be
- * seen in the wrong order. However since we call wake_up_all
- * in that case, this will hopefully not pose a problem,
- * and the worst case would only cause someone to accidentally
- * hit -EAGAIN in ttm_bo_reserve when they see old value of
- * val_seq. However this would only happen if seq_valid was
- * written before val_seq was, and just means some slightly
- * increased cpu usage
- */
- bo->val_seq = ticket->stamp;
- bo->seq_valid = true;
- if (wake_up)
- wake_up_all(&bo->event_queue);
- } else {
- bo->seq_valid = false;
+ success = ww_mutex_trylock(&bo->resv->lock);
+ return success ? 0 : -EBUSY;
}
- return 0;
+ if (interruptible)
+ ret = ww_mutex_lock_interruptible(&bo->resv->lock,
+ ticket);
+ else
+ ret = ww_mutex_lock(&bo->resv->lock, ticket);
+ if (ret == -EINTR)
+ return -ERESTARTSYS;
+ return ret;
}
EXPORT_SYMBOL(ttm_bo_reserve);
@@ -313,50 +266,27 @@ int ttm_bo_reserve(struct ttm_buffer_object *bo,
return ret;
}
-int ttm_bo_reserve_slowpath_nolru(struct ttm_buffer_object *bo,
- bool interruptible,
- struct ww_acquire_ctx *ticket)
-{
- bool wake_up = false;
- int ret;
-
- while (unlikely(atomic_xchg(&bo->reserved, 1) != 0)) {
- WARN_ON(bo->seq_valid && ticket->stamp == bo->val_seq);
-
- ret = ttm_bo_wait_unreserved(bo, interruptible);
-
- if (unlikely(ret))
- return ret;
- }
-
- if (bo->val_seq - ticket->stamp < LONG_MAX || !bo->seq_valid)
- wake_up = true;
-
- /**
- * Wake up waiters that may need to recheck for deadlock,
- * if we decreased the sequence number.
- */
- bo->val_seq = ticket->stamp;
- bo->seq_valid = true;
- if (wake_up)
- wake_up_all(&bo->event_queue);
-
- return 0;
-}
-
int ttm_bo_reserve_slowpath(struct ttm_buffer_object *bo,
bool interruptible, struct ww_acquire_ctx *ticket)
{
struct ttm_bo_global *glob = bo->glob;
- int put_count, ret;
+ int put_count = 0;
+ int ret = 0;
+
+ if (interruptible)
+ ret = ww_mutex_lock_slow_interruptible(&bo->resv->lock,
+ ticket);
+ else
+ ww_mutex_lock_slow(&bo->resv->lock, ticket);
- ret = ttm_bo_reserve_slowpath_nolru(bo, interruptible, ticket);
- if (likely(!ret)) {
+ if (likely(ret == 0)) {
spin_lock(&glob->lru_lock);
put_count = ttm_bo_del_from_lru(bo);
spin_unlock(&glob->lru_lock);
ttm_bo_list_ref_sub(bo, put_count, true);
- }
+ } else if (ret == -EINTR)
+ ret = -ERESTARTSYS;
+
return ret;
}
EXPORT_SYMBOL(ttm_bo_reserve_slowpath);
@@ -364,8 +294,7 @@ EXPORT_SYMBOL(ttm_bo_reserve_slowpath);
void ttm_bo_unreserve_ticket_locked(struct ttm_buffer_object *bo, struct ww_acquire_ctx *ticket)
{
ttm_bo_add_to_lru(bo);
- atomic_set(&bo->reserved, 0);
- wake_up_all(&bo->event_queue);
+ ww_mutex_unlock(&bo->resv->lock);
}
void ttm_bo_unreserve(struct ttm_buffer_object *bo)
@@ -558,17 +487,7 @@ static void ttm_bo_cleanup_memtype_use(struct ttm_buffer_object *bo)
}
ttm_bo_mem_put(bo, &bo->mem);
- atomic_set(&bo->reserved, 0);
- wake_up_all(&bo->event_queue);
-
- /*
- * Since the final reference to this bo may not be dropped by
- * the current task we have to put a memory barrier here to make
- * sure the changes done in this function are always visible.
- *
- * This function only needs protection against the final kref_put.
- */
- smp_mb__before_atomic_dec();
+ ww_mutex_unlock (&bo->resv->lock);
}
static void ttm_bo_cleanup_refs_or_queue(struct ttm_buffer_object *bo)
@@ -600,10 +519,8 @@ static void ttm_bo_cleanup_refs_or_queue(struct ttm_buffer_object *bo)
sync_obj = driver->sync_obj_ref(bo->sync_obj);
spin_unlock(&bdev->fence_lock);
- if (!ret) {
- atomic_set(&bo->reserved, 0);
- wake_up_all(&bo->event_queue);
- }
+ if (!ret)
+ ww_mutex_unlock(&bo->resv->lock);
kref_get(&bo->list_kref);
list_add_tail(&bo->ddestroy, &bdev->ddestroy);
@@ -653,8 +570,7 @@ static int ttm_bo_cleanup_refs_and_unlock(struct ttm_buffer_object *bo,
sync_obj = driver->sync_obj_ref(bo->sync_obj);
spin_unlock(&bdev->fence_lock);
- atomic_set(&bo->reserved, 0);
- wake_up_all(&bo->event_queue);
+ ww_mutex_unlock(&bo->resv->lock);
spin_unlock(&glob->lru_lock);
ret = driver->sync_obj_wait(sync_obj, false, interruptible);
@@ -692,8 +608,7 @@ static int ttm_bo_cleanup_refs_and_unlock(struct ttm_buffer_object *bo,
spin_unlock(&bdev->fence_lock);
if (ret || unlikely(list_empty(&bo->ddestroy))) {
- atomic_set(&bo->reserved, 0);
- wake_up_all(&bo->event_queue);
+ ww_mutex_unlock(&bo->resv->lock);
spin_unlock(&glob->lru_lock);
return ret;
}
@@ -1253,6 +1168,7 @@ int ttm_bo_init(struct ttm_bo_device *bdev,
int ret = 0;
unsigned long num_pages;
struct ttm_mem_global *mem_glob = bdev->glob->mem_glob;
+ bool locked;
ret = ttm_mem_global_alloc(mem_glob, acc_size, false, false);
if (ret) {
@@ -1279,8 +1195,6 @@ int ttm_bo_init(struct ttm_bo_device *bdev,
kref_init(&bo->kref);
kref_init(&bo->list_kref);
atomic_set(&bo->cpu_writers, 0);
- atomic_set(&bo->reserved, 1);
- init_waitqueue_head(&bo->event_queue);
INIT_LIST_HEAD(&bo->lru);
INIT_LIST_HEAD(&bo->ddestroy);
INIT_LIST_HEAD(&bo->swap);
@@ -1298,37 +1212,34 @@ int ttm_bo_init(struct ttm_bo_device *bdev,
bo->mem.bus.io_reserved_count = 0;
bo->priv_flags = 0;
bo->mem.placement = (TTM_PL_FLAG_SYSTEM | TTM_PL_FLAG_CACHED);
- bo->seq_valid = false;
bo->persistent_swap_storage = persistent_swap_storage;
bo->acc_size = acc_size;
bo->sg = sg;
+ bo->resv = &bo->ttm_resv;
+ reservation_object_init(bo->resv);
atomic_inc(&bo->glob->bo_count);
ret = ttm_bo_check_placement(bo, placement);
- if (unlikely(ret != 0))
- goto out_err;
/*
* For ttm_bo_type_device buffers, allocate
* address space from the device.
*/
- if (bo->type == ttm_bo_type_device ||
- bo->type == ttm_bo_type_sg) {
+ if (likely(!ret) &&
+ (bo->type == ttm_bo_type_device ||
+ bo->type == ttm_bo_type_sg))
ret = ttm_bo_setup_vm(bo);
- if (ret)
- goto out_err;
- }
- ret = ttm_bo_validate(bo, placement, interruptible, false);
- if (ret)
- goto out_err;
+ locked = ww_mutex_trylock(&bo->resv->lock);
+ WARN_ON(!locked);
- ttm_bo_unreserve(bo);
- return 0;
+ if (likely(!ret))
+ ret = ttm_bo_validate(bo, placement, interruptible, false);
-out_err:
ttm_bo_unreserve(bo);
- ttm_bo_unref(&bo);
+
+ if (unlikely(ret))
+ ttm_bo_unref(&bo);
return ret;
}
@@ -1941,8 +1852,7 @@ out:
* already swapped buffer.
*/
- atomic_set(&bo->reserved, 0);
- wake_up_all(&bo->event_queue);
+ ww_mutex_unlock(&bo->resv->lock);
kref_put(&bo->list_kref, ttm_bo_release_list);
return ret;
}
diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index af89458..319cf41 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -433,6 +433,7 @@ static int ttm_buffer_object_transfer(struct ttm_buffer_object *bo,
struct ttm_buffer_object *fbo;
struct ttm_bo_device *bdev = bo->bdev;
struct ttm_bo_driver *driver = bdev->driver;
+ int ret;
fbo = kmalloc(sizeof(*fbo), GFP_KERNEL);
if (!fbo)
@@ -445,7 +446,6 @@ static int ttm_buffer_object_transfer(struct ttm_buffer_object *bo,
* TODO: Explicit member copy would probably be better here.
*/
- init_waitqueue_head(&fbo->event_queue);
INIT_LIST_HEAD(&fbo->ddestroy);
INIT_LIST_HEAD(&fbo->lru);
INIT_LIST_HEAD(&fbo->swap);
@@ -463,6 +463,10 @@ static int ttm_buffer_object_transfer(struct ttm_buffer_object *bo,
kref_init(&fbo->kref);
fbo->destroy = &ttm_transfered_destroy;
fbo->acc_size = 0;
+ fbo->resv = &fbo->ttm_resv;
+ reservation_object_init(fbo->resv);
+ ret = ww_mutex_trylock(&fbo->resv->lock);
+ WARN_ON(!ret);
*new_obj = fbo;
return 0;
diff --git a/drivers/gpu/drm/ttm/ttm_execbuf_util.c b/drivers/gpu/drm/ttm/ttm_execbuf_util.c
index efcb734..7392da5 100644
--- a/drivers/gpu/drm/ttm/ttm_execbuf_util.c
+++ b/drivers/gpu/drm/ttm/ttm_execbuf_util.c
@@ -48,8 +48,7 @@ static void ttm_eu_backoff_reservation_locked(struct list_head *list,
entry->removed = false;
} else {
- atomic_set(&bo->reserved, 0);
- wake_up_all(&bo->event_queue);
+ ww_mutex_unlock(&bo->resv->lock);
}
}
}
@@ -134,8 +133,6 @@ int ttm_eu_reserve_buffers(struct ww_acquire_ctx *ticket,
glob = entry->bo->glob;
ww_acquire_init(ticket, &reservation_ww_class);
- spin_lock(&glob->lru_lock);
-
retry:
list_for_each_entry(entry, list, head) {
struct ttm_buffer_object *bo = entry->bo;
@@ -144,42 +141,34 @@ retry:
if (entry->reserved)
continue;
- ret = ttm_bo_reserve_nolru(bo, true, true, true, ticket);
- switch (ret) {
- case 0:
- break;
- case -EBUSY:
- ttm_eu_del_from_lru_locked(list);
- spin_unlock(&glob->lru_lock);
- ret = ttm_bo_reserve_nolru(bo, true, false,
- true, ticket);
- spin_lock(&glob->lru_lock);
-
- if (!ret)
- break;
- if (unlikely(ret != -EAGAIN))
- goto err;
+ ret = ttm_bo_reserve_nolru(bo, true, false, true, ticket);
- /* fallthrough */
- case -EAGAIN:
+ if (ret == -EDEADLK) {
+ /* uh oh, we lost out, drop every reservation and try
+ * to only reserve this buffer, then start over if
+ * this succeeds.
+ */
+ spin_lock(&glob->lru_lock);
ttm_eu_backoff_reservation_locked(list, ticket);
spin_unlock(&glob->lru_lock);
ttm_eu_list_ref_sub(list);
- ret = ttm_bo_reserve_slowpath_nolru(bo, true, ticket);
- if (unlikely(ret != 0))
+ ret = ww_mutex_lock_slow_interruptible(&bo->resv->lock,
+ ticket);
+ if (unlikely(ret != 0)) {
+ if (ret == -EINTR)
+ ret = -ERESTARTSYS;
goto err_fini;
+ }
- spin_lock(&glob->lru_lock);
entry->reserved = true;
if (unlikely(atomic_read(&bo->cpu_writers) > 0)) {
ret = -EBUSY;
goto err;
}
goto retry;
- default:
+ } else if (ret)
goto err;
- }
entry->reserved = true;
if (unlikely(atomic_read(&bo->cpu_writers) > 0)) {
@@ -189,12 +178,14 @@ retry:
}
ww_acquire_done(ticket);
+ spin_lock(&glob->lru_lock);
ttm_eu_del_from_lru_locked(list);
spin_unlock(&glob->lru_lock);
ttm_eu_list_ref_sub(list);
return 0;
err:
+ spin_lock(&glob->lru_lock);
ttm_eu_backoff_reservation_locked(list, ticket);
spin_unlock(&glob->lru_lock);
ttm_eu_list_ref_sub(list);
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index 0a992b0..31ad860 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -39,6 +39,7 @@
#include <linux/mm.h>
#include <linux/rbtree.h>
#include <linux/bitmap.h>
+#include <linux/reservation.h>
struct ttm_bo_device;
@@ -153,7 +154,6 @@ struct ttm_tt;
* Lru lists may keep one refcount, the delayed delete list, and kref != 0
* keeps one refcount. When this refcount reaches zero,
* the object is destroyed.
- * @event_queue: Queue for processes waiting on buffer object status change.
* @mem: structure describing current placement.
* @persistent_swap_storage: Usually the swap storage is deleted for buffers
* pinned in physical memory. If this behaviour is not desired, this member
@@ -164,12 +164,6 @@ struct ttm_tt;
* @lru: List head for the lru list.
* @ddestroy: List head for the delayed destroy list.
* @swap: List head for swap LRU list.
- * @val_seq: Sequence of the validation holding the @reserved lock.
- * Used to avoid starvation when many processes compete to validate the
- * buffer. This member is protected by the bo_device::lru_lock.
- * @seq_valid: The value of @val_seq is valid. This value is protected by
- * the bo_device::lru_lock.
- * @reserved: Deadlock-free lock used for synchronization state transitions.
* @sync_obj: Pointer to a synchronization object.
* @priv_flags: Flags describing buffer object internal state.
* @vm_rb: Rb node for the vm rb tree.
@@ -209,10 +203,9 @@ struct ttm_buffer_object {
struct kref kref;
struct kref list_kref;
- wait_queue_head_t event_queue;
/**
- * Members protected by the bo::reserved lock.
+ * Members protected by the bo::resv::reserved lock.
*/
struct ttm_mem_reg mem;
@@ -234,15 +227,6 @@ struct ttm_buffer_object {
struct list_head ddestroy;
struct list_head swap;
struct list_head io_reserve_lru;
- unsigned long val_seq;
- bool seq_valid;
-
- /**
- * Members protected by the bdev::lru_lock
- * only when written to.
- */
-
- atomic_t reserved;
/**
* Members protected by struct buffer_object_device::fence_lock
@@ -272,6 +256,9 @@ struct ttm_buffer_object {
uint32_t cur_placement;
struct sg_table *sg;
+
+ struct reservation_object *resv;
+ struct reservation_object ttm_resv;
};
/**
@@ -736,7 +723,7 @@ extern void ttm_bo_swapout_all(struct ttm_bo_device *bdev);
*/
static inline bool ttm_bo_is_reserved(struct ttm_buffer_object *bo)
{
- return atomic_read(&bo->reserved);
+ return ww_mutex_is_locked(&bo->resv->lock);
}
#endif
diff --git a/include/drm/ttm/ttm_execbuf_util.h b/include/drm/ttm/ttm_execbuf_util.h
index ba71ef9..ec8a1d3 100644
--- a/include/drm/ttm/ttm_execbuf_util.h
+++ b/include/drm/ttm/ttm_execbuf_util.h
@@ -33,7 +33,6 @@
#include <ttm/ttm_bo_api.h>
#include <linux/list.h>
-#include <linux/reservation.h>
/**
* struct ttm_validate_buffer
--
1.8.3.1
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