drm/amdgpu: Optimize mutex usage (v3)

Submitted by Xie, AlexBin on June 16, 2017, 1:08 p.m.

Details

Message ID 1497618511-3975-1-git-send-email-AlexBin.Xie@amd.com
State New
Headers show
Series "drm/amdgpu: Optimize mutex usage (v3)" ( rev: 1 ) in AMD X.Org drivers

Not browsing as part of any series.

Commit Message

Xie, AlexBin June 16, 2017, 1:08 p.m.
In original function amdgpu_bo_list_get, the waiting
for result->lock can be quite long while mutex
bo_list_lock was holding. It can make other tasks
waiting for bo_list_lock for long period.

Secondly, this patch allows several tasks(readers of idr)
to proceed at the same time.

v2: use rcu and kref (Dave Airlie and Christian König)
v3: update v1 commit message (Michel Dänzer)

Signed-off-by: Alex Xie <AlexBin.Xie@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu.h         |  2 ++
 drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c | 40 ++++++++++++++++++++---------
 2 files changed, 30 insertions(+), 12 deletions(-)

Patch hide | download patch | download mbox

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index 063fc73..e9b3981 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -871,6 +871,8 @@  struct amdgpu_fpriv {
 
 struct amdgpu_bo_list {
 	struct mutex lock;
+	struct rcu_head rhead;
+	struct kref refcount;
 	struct amdgpu_bo *gds_obj;
 	struct amdgpu_bo *gws_obj;
 	struct amdgpu_bo *oa_obj;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
index 5af956f..efa6903 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
@@ -41,6 +41,20 @@  static int amdgpu_bo_list_set(struct amdgpu_device *adev,
 				     struct drm_amdgpu_bo_list_entry *info,
 				     unsigned num_entries);
 
+static void amdgpu_bo_list_release_rcu(struct kref *ref)
+{
+	unsigned i;
+	struct amdgpu_bo_list *list = container_of(ref, struct amdgpu_bo_list,
+						   refcount);
+
+	for (i = 0; i < list->num_entries; ++i)
+		amdgpu_bo_unref(&list->array[i].robj);
+
+	mutex_destroy(&list->lock);
+	drm_free_large(list->array);
+	kfree_rcu(list, rhead);
+}
+
 static int amdgpu_bo_list_create(struct amdgpu_device *adev,
 				 struct drm_file *filp,
 				 struct drm_amdgpu_bo_list_entry *info,
@@ -57,7 +71,7 @@  static int amdgpu_bo_list_create(struct amdgpu_device *adev,
 
 	/* initialize bo list*/
 	mutex_init(&list->lock);
-
+	kref_init(&list->refcount);
 	r = amdgpu_bo_list_set(adev, filp, list, info, num_entries);
 	if (r) {
 		kfree(list);
@@ -83,14 +97,9 @@  static void amdgpu_bo_list_destroy(struct amdgpu_fpriv *fpriv, int id)
 
 	mutex_lock(&fpriv->bo_list_lock);
 	list = idr_remove(&fpriv->bo_list_handles, id);
-	if (list) {
-		/* Another user may have a reference to this list still */
-		mutex_lock(&list->lock);
-		mutex_unlock(&list->lock);
-		amdgpu_bo_list_free(list);
-	}
-
 	mutex_unlock(&fpriv->bo_list_lock);
+	if (list)
+		kref_put(&list->refcount, amdgpu_bo_list_release_rcu);
 }
 
 static int amdgpu_bo_list_set(struct amdgpu_device *adev,
@@ -185,11 +194,17 @@  amdgpu_bo_list_get(struct amdgpu_fpriv *fpriv, int id)
 {
 	struct amdgpu_bo_list *result;
 
-	mutex_lock(&fpriv->bo_list_lock);
+	rcu_read_lock();
 	result = idr_find(&fpriv->bo_list_handles, id);
-	if (result)
-		mutex_lock(&result->lock);
-	mutex_unlock(&fpriv->bo_list_lock);
+
+	if (result) {
+		if (kref_get_unless_zero(&result->refcount))
+			mutex_lock(&result->lock);
+		else
+			result = NULL;
+	}
+	rcu_read_unlock();
+
 	return result;
 }
 
@@ -227,6 +242,7 @@  void amdgpu_bo_list_get_list(struct amdgpu_bo_list *list,
 void amdgpu_bo_list_put(struct amdgpu_bo_list *list)
 {
 	mutex_unlock(&list->lock);
+	kref_put(&list->refcount, amdgpu_bo_list_release_rcu);
 }
 
 void amdgpu_bo_list_free(struct amdgpu_bo_list *list)

Comments

On 16 June 2017 at 23:08, Alex Xie <AlexBin.Xie@amd.com> wrote:
> In original function amdgpu_bo_list_get, the waiting
> for result->lock can be quite long while mutex
> bo_list_lock was holding. It can make other tasks
> waiting for bo_list_lock for long period.
>
> Secondly, this patch allows several tasks(readers of idr)
> to proceed at the same time.
>
> v2: use rcu and kref (Dave Airlie and Christian König)
> v3: update v1 commit message (Michel Dänzer)

Got this, I'm guessing due to this patch.

Dave.

[  141.965723] =============================
[  141.965724] WARNING: suspicious RCU usage
[  141.965726] 4.12.0-rc7 #221 Not tainted
[  141.965727] -----------------------------
[  141.965728] /home/airlied/devel/kernel/linux-2.6/include/linux/rcupdate.h:531
Illegal context switch in RCU read-side critical section!
[  141.965730]
               other info that might help us debug this:

[  141.965731]
               rcu_scheduler_active = 2, debug_locks = 0
[  141.965732] 1 lock held by amdgpu_cs:0/1332:
[  141.965733]  #0:  (rcu_read_lock){......}, at: [<ffffffffa01a0d07>]
amdgpu_bo_list_get+0x0/0x109 [amdgpu]
[  141.965774]
               stack backtrace:
[  141.965776] CPU: 6 PID: 1332 Comm: amdgpu_cs:0 Not tainted 4.12.0-rc7 #221
[  141.965777] Hardware name: To be filled by O.E.M. To be filled by
O.E.M./M5A97 R2.0, BIOS 2603 06/26/2015
[  141.965778] Call Trace:
[  141.965782]  dump_stack+0x68/0x92
[  141.965785]  lockdep_rcu_suspicious+0xf7/0x100
[  141.965788]  ___might_sleep+0x56/0x1fc
[  141.965790]  __might_sleep+0x68/0x6f
[  141.965793]  __mutex_lock+0x4e/0x7b5
[  141.965817]  ? amdgpu_bo_list_get+0xa4/0x109 [amdgpu]
[  141.965820]  ? lock_acquire+0x125/0x1b9
[  141.965844]  ? amdgpu_bo_list_set+0x464/0x464 [amdgpu]
[  141.965846]  mutex_lock_nested+0x16/0x18
[  141.965848]  ? mutex_lock_nested+0x16/0x18
[  141.965872]  amdgpu_bo_list_get+0xa4/0x109 [amdgpu]
[  141.965895]  amdgpu_cs_ioctl+0x4a0/0x17dd [amdgpu]
[  141.965898]  ? radix_tree_node_alloc.constprop.11+0x77/0xab
[  141.965916]  drm_ioctl+0x264/0x393 [drm]
[  141.965939]  ? amdgpu_cs_find_mapping+0x83/0x83 [amdgpu]
[  141.965942]  ? trace_hardirqs_on_caller+0x16a/0x186


>
> Signed-off-by: Alex Xie <AlexBin.Xie@amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu.h         |  2 ++
>  drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c | 40 ++++++++++++++++++++---------
>  2 files changed, 30 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index 063fc73..e9b3981 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -871,6 +871,8 @@ struct amdgpu_fpriv {
>
>  struct amdgpu_bo_list {
>         struct mutex lock;
> +       struct rcu_head rhead;
> +       struct kref refcount;
>         struct amdgpu_bo *gds_obj;
>         struct amdgpu_bo *gws_obj;
>         struct amdgpu_bo *oa_obj;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
> index 5af956f..efa6903 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
> @@ -41,6 +41,20 @@ static int amdgpu_bo_list_set(struct amdgpu_device *adev,
>                                      struct drm_amdgpu_bo_list_entry *info,
>                                      unsigned num_entries);
>
> +static void amdgpu_bo_list_release_rcu(struct kref *ref)
> +{
> +       unsigned i;
> +       struct amdgpu_bo_list *list = container_of(ref, struct amdgpu_bo_list,
> +                                                  refcount);
> +
> +       for (i = 0; i < list->num_entries; ++i)
> +               amdgpu_bo_unref(&list->array[i].robj);
> +
> +       mutex_destroy(&list->lock);
> +       drm_free_large(list->array);
> +       kfree_rcu(list, rhead);
> +}
> +
>  static int amdgpu_bo_list_create(struct amdgpu_device *adev,
>                                  struct drm_file *filp,
>                                  struct drm_amdgpu_bo_list_entry *info,
> @@ -57,7 +71,7 @@ static int amdgpu_bo_list_create(struct amdgpu_device *adev,
>
>         /* initialize bo list*/
>         mutex_init(&list->lock);
> -
> +       kref_init(&list->refcount);
>         r = amdgpu_bo_list_set(adev, filp, list, info, num_entries);
>         if (r) {
>                 kfree(list);
> @@ -83,14 +97,9 @@ static void amdgpu_bo_list_destroy(struct amdgpu_fpriv *fpriv, int id)
>
>         mutex_lock(&fpriv->bo_list_lock);
>         list = idr_remove(&fpriv->bo_list_handles, id);
> -       if (list) {
> -               /* Another user may have a reference to this list still */
> -               mutex_lock(&list->lock);
> -               mutex_unlock(&list->lock);
> -               amdgpu_bo_list_free(list);
> -       }
> -
>         mutex_unlock(&fpriv->bo_list_lock);
> +       if (list)
> +               kref_put(&list->refcount, amdgpu_bo_list_release_rcu);
>  }
>
>  static int amdgpu_bo_list_set(struct amdgpu_device *adev,
> @@ -185,11 +194,17 @@ amdgpu_bo_list_get(struct amdgpu_fpriv *fpriv, int id)
>  {
>         struct amdgpu_bo_list *result;
>
> -       mutex_lock(&fpriv->bo_list_lock);
> +       rcu_read_lock();
>         result = idr_find(&fpriv->bo_list_handles, id);
> -       if (result)
> -               mutex_lock(&result->lock);
> -       mutex_unlock(&fpriv->bo_list_lock);
> +
> +       if (result) {
> +               if (kref_get_unless_zero(&result->refcount))
> +                       mutex_lock(&result->lock);
> +               else
> +                       result = NULL;
> +       }
> +       rcu_read_unlock();
> +
>         return result;
>  }
>
> @@ -227,6 +242,7 @@ void amdgpu_bo_list_get_list(struct amdgpu_bo_list *list,
>  void amdgpu_bo_list_put(struct amdgpu_bo_list *list)
>  {
>         mutex_unlock(&list->lock);
> +       kref_put(&list->refcount, amdgpu_bo_list_release_rcu);
>  }
>
>  void amdgpu_bo_list_free(struct amdgpu_bo_list *list)
> --
> 2.7.4
>
> _______________________________________________
> amd-gfx mailing list
> amd-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/amd-gfx