Re: [PATCH 1/3] drm/ttm: fix ttm_bo_bulk_move_helper

2018-09-08 Thread Christian König 

Am 08.09.2018 um 09:54 schrieb Huang Rui:

On Fri, Sep 07, 2018 at 07:18:59PM +0800, Christian K�nig wrote:

Am 07.09.2018 um 13:02 schrieb Huang, Ray:

  Yes, that was one problem. Another was that the cutting code was 
buggy
   and determined one of the positions to cut at the wrong time.

 I went through again about the list cutting behavior and wrote down with 
the attached picture.
 After do the second list_cut_position, the list2 should be point the end of 
"before" list. And list2 won't be used anymore after list cutting. May I know 
am I something missed?


Let's take a look at the original code:

 list1 = is_swap ? >last->swap : >last->lru;
 list2 = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
  
 list_cut_position(, lru, list1);

 list_cut_position(, , list2);


As far as I can see the problem is that the first list_cur_position could
modify the value of pos->first->lru.prev and so make the second
list_cut_position work on the wrong position.


I think I understood. In this case (the first element of LRU ==
pos->first->lru), please see the picture. If we store first->lru.prev as
list2(LRU head), after do list cutting, the first->lru.prev will overwrite
as new head (entries), however, the orignal list2 will still point previous
head (that is the wrong position now). We actually expected to use the
latest first->lru.prev as the second cutting position. So we should adjust
code sequence like below:

list1 = is_swap ? >last->swap : >last->lru;
list_cut_position(, lru, list1);

list2 = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
list_cut_position(, , list2);

Am I understanding right?


Yes, exactly. And the fix looks like what I did as well. Just only used 
one variable and added some extra BUG_ON().


Christian.



Thanks,
Ray


Regards,
Christian.



 Thanks,
 Ray

 From: amd-gfx  on behalf of Christian 
König 
 Sent: Thursday, September 6, 2018 6:06 PM
 To: Huang, Ray
     Cc: Michel Dänzer; amd-gfx@lists.freedesktop.org
 Subject: Re: [PATCH 1/3] drm/ttm: fix ttm_bo_bulk_move_helper
  


 Am 06.09.2018 um 12:02 schrieb Huang Rui:

 On Fri, Aug 31, 2018 at 05:17:33PM +0200, Christian König wrote:

 Am 31.08.2018 um 17:15 schrieb Michel Dänzer:

 On 2018-08-31 3:10 p.m., Christian König wrote:

 Staring at the function for six hours, just to essentially 
move one line
 of code.

 That sucks, but the commit log should describe what the 
problem was and
 how this patch solves it.



 Signed-off-by: Christian König 
 ---
drivers/gpu/drm/ttm/ttm_bo.c | 13 -
1 file changed, 8 insertions(+), 5 deletions(-)

 diff --git a/drivers/gpu/drm/ttm/ttm_bo.c 
b/drivers/gpu/drm/ttm/ttm_bo.c
 index 35d53d81f486..138c98902033 100644
 --- a/drivers/gpu/drm/ttm/ttm_bo.c
 +++ b/drivers/gpu/drm/ttm/ttm_bo.c
 @@ -250,15 +250,18 @@ 
EXPORT_SYMBOL(ttm_bo_move_to_lru_tail);
static void ttm_bo_bulk_move_helper(struct 
ttm_lru_bulk_move_pos *pos,
  struct list_head *lru, 
bool is_swap)
{
 +  struct list_head *list;
  LIST_HEAD(entries);
  LIST_HEAD(before);
 -  struct list_head *list1, *list2;
 -  list1 = is_swap ? >last->swap : >last->lru;
 -  list2 = is_swap ? pos->first->swap.prev : 
pos->first->lru.prev;
 +  reservation_object_assert_held(pos->last->resv);
 +  list = is_swap ? >last->swap : >last->lru;
 +  list_cut_position(, lru, list);
 +
 +  reservation_object_assert_held(pos->first->resv);
 +  list = is_swap ? pos->first->swap.prev : 
pos->first->lru.prev;
 +  list_cut_position(, , list);

 So the problem was that the first list_cut_position call could 
result in
 list2 pointing to la-la-land? Good catch!

 Yes, exactly. Thought that would be obvious, but going to add that
 to the commit log.

 Can I get a tested-by? You where much better at reproducing that 
than I'm.


 Michel, Christian, thanks so much to take care of this when I was on
 vacation. And sorry to let you take a long time for finding the cause.

 Is that because I didn't hold the resveration before cut the list from
 position "first" and &

Re: [PATCH 1/3] drm/ttm: fix ttm_bo_bulk_move_helper

2018-09-08 Thread Huang Rui 
On Fri, Sep 07, 2018 at 07:18:59PM +0800, Christian K�nig wrote:
> Am 07.09.2018 um 13:02 schrieb Huang, Ray:
> 
>  Yes, that was one problem. Another was that the cutting code was 
> buggy 
>   and determined one of the positions to cut at the wrong time.
> 
> I went through again about the list cutting behavior and wrote down with 
> the attached picture.
> After do the second list_cut_position, the list2 should be point the end 
> of "before" list. And list2 won't be used anymore after list cutting. May I 
> know am I something missed? 
> 
> 
> Let's take a look at the original code:
> 
> list1 = is_swap ? >last->swap : >last->lru;
> list2 = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
>  
> list_cut_position(, lru, list1);
> list_cut_position(, , list2);
> 
> 
> As far as I can see the problem is that the first list_cur_position could
> modify the value of pos->first->lru.prev and so make the second
> list_cut_position work on the wrong position.
> 

I think I understood. In this case (the first element of LRU ==
pos->first->lru), please see the picture. If we store first->lru.prev as
list2(LRU head), after do list cutting, the first->lru.prev will overwrite
as new head (entries), however, the orignal list2 will still point previous
head (that is the wrong position now). We actually expected to use the
latest first->lru.prev as the second cutting position. So we should adjust
code sequence like below:

list1 = is_swap ? >last->swap : >last->lru;
list_cut_position(, lru, list1);

list2 = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
list_cut_position(, , list2);

Am I understanding right?

Thanks,
Ray

> Regards,
> Christian.
> 
> 
> 
> Thanks,
> Ray
> 
> From: amd-gfx  on behalf of 
> Christian König 
> Sent: Thursday, September 6, 2018 6:06 PM
> To: Huang, Ray
> Cc: Michel Dänzer; amd-gfx@lists.freedesktop.org
> Subject: Re: [PATCH 1/3] drm/ttm: fix ttm_bo_bulk_move_helper
>  
> 
> Am 06.09.2018 um 12:02 schrieb Huang Rui:
> 
> On Fri, Aug 31, 2018 at 05:17:33PM +0200, Christian König wrote:
> 
> Am 31.08.2018 um 17:15 schrieb Michel Dänzer:
> 
> On 2018-08-31 3:10 p.m., Christian König wrote:
> 
> Staring at the function for six hours, just to 
> essentially move one line
> of code.
> 
> That sucks, but the commit log should describe what the 
> problem was and
> how this patch solves it.
> 
> 
> 
> Signed-off-by: Christian König 
> ---
>drivers/gpu/drm/ttm/ttm_bo.c | 13 -
>1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c 
> b/drivers/gpu/drm/ttm/ttm_bo.c
> index 35d53d81f486..138c98902033 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -250,15 +250,18 @@ 
> EXPORT_SYMBOL(ttm_bo_move_to_lru_tail);
>static void ttm_bo_bulk_move_helper(struct 
> ttm_lru_bulk_move_pos *pos,
>  struct list_head *lru, 
> bool is_swap)
>{
> +  struct list_head *list;
>  LIST_HEAD(entries);
>  LIST_HEAD(before);
> -  struct list_head *list1, *list2;
> -  list1 = is_swap ? >last->swap : >last->lru;
> -  list2 = is_swap ? pos->first->swap.prev : 
> pos->first->lru.prev;
> +  reservation_object_assert_held(pos->last->resv);
> +  list = is_swap ? >last->swap : >last->lru;
> +  list_cut_position(, lru, list);
> +
> +  reservation_object_assert_held(pos->first->resv);
> +  list = is_swap ? pos->first->swap.prev : 
> pos->first->lru.prev;
> +  list_cut_position(, , list);
> 
> So the problem was that the first list_cut_position call 
> could result in
> list2 pointing to la-la-land? Good catch!
> 
> Yes, exactly. Thought that would be obvious, but going to add that
> to the commit log.
> 
> Can I get a tested-by? You where much better at reproducing that 
>

Re: [PATCH 1/3] drm/ttm: fix ttm_bo_bulk_move_helper

2018-09-07 Thread Christian König 

Am 07.09.2018 um 13:02 schrieb Huang, Ray:

  Yes, that was one problem. Another was that the cutting code was buggy
   and determined one of the positions to cut at the wrong time.

I went through again about the list cutting behavior and wrote down with the 
attached picture.
After do the second list_cut_position, the list2 should be point the end of 
"before" list. And list2 won't be used anymore after list cutting. May I know 
am I something missed?


Let's take a look at the original code:

list1 = is_swap ? >last->swap : >last->lru;
list2 = is_swap ? pos->first->swap.prev : pos->first->lru.prev;

list_cut_position(, lru, list1);
list_cut_position(, , list2);


As far as I can see the problem is that the first list_cur_position 
could modify the value of pos->first->lru.prev and so make the second 
list_cut_position work on the wrong position.


Regards,
Christian.



Thanks,
Ray

From: amd-gfx  on behalf of Christian König 

Sent: Thursday, September 6, 2018 6:06 PM
To: Huang, Ray
Cc: Michel Dänzer; amd-gfx@lists.freedesktop.org
Subject: Re: [PATCH 1/3] drm/ttm: fix ttm_bo_bulk_move_helper
   


Am 06.09.2018 um 12:02 schrieb Huang Rui:

On Fri, Aug 31, 2018 at 05:17:33PM +0200, Christian König wrote:

Am 31.08.2018 um 17:15 schrieb Michel Dänzer:

On 2018-08-31 3:10 p.m., Christian König wrote:

Staring at the function for six hours, just to essentially move one line
of code.

That sucks, but the commit log should describe what the problem was and
how this patch solves it.



Signed-off-by: Christian König 
---
    drivers/gpu/drm/ttm/ttm_bo.c | 13 -
    1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 35d53d81f486..138c98902033 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -250,15 +250,18 @@ EXPORT_SYMBOL(ttm_bo_move_to_lru_tail);
    static void ttm_bo_bulk_move_helper(struct ttm_lru_bulk_move_pos *pos,
  struct list_head *lru, bool is_swap)
    {
+  struct list_head *list;
  LIST_HEAD(entries);
  LIST_HEAD(before);
-  struct list_head *list1, *list2;
-  list1 = is_swap ? >last->swap : >last->lru;
-  list2 = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
+  reservation_object_assert_held(pos->last->resv);
+  list = is_swap ? >last->swap : >last->lru;
+  list_cut_position(, lru, list);
+
+  reservation_object_assert_held(pos->first->resv);
+  list = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
+  list_cut_position(, , list);

So the problem was that the first list_cut_position call could result in
list2 pointing to la-la-land? Good catch!

Yes, exactly. Thought that would be obvious, but going to add that
to the commit log.

Can I get a tested-by? You where much better at reproducing that than I'm.


Michel, Christian, thanks so much to take care of this when I was on
vacation. And sorry to let you take a long time for finding the cause.

Is that because I didn't hold the resveration before cut the list from
position "first" and "last"?

Yes, that was one problem. Another was that the cutting code was buggy
and determined one of the positions to cut at the wrong time.


    May I know in which cases, we must hold the
bo's reservation firstly?

BOs are reserved to prevent moving them. E.g. when the BO isn't reserved
it can move around and so the LRU where you want to add/remove it could
change.

Christian.


Thanks,
Ray



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Re: [PATCH 1/3] drm/ttm: fix ttm_bo_bulk_move_helper

2018-09-06 Thread Christian König 

Am 06.09.2018 um 12:02 schrieb Huang Rui:

On Fri, Aug 31, 2018 at 05:17:33PM +0200, Christian König wrote:

Am 31.08.2018 um 17:15 schrieb Michel Dänzer:

On 2018-08-31 3:10 p.m., Christian König wrote:

Staring at the function for six hours, just to essentially move one line
of code.

That sucks, but the commit log should describe what the problem was and
how this patch solves it.



Signed-off-by: Christian König 
---
  drivers/gpu/drm/ttm/ttm_bo.c | 13 -
  1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 35d53d81f486..138c98902033 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -250,15 +250,18 @@ EXPORT_SYMBOL(ttm_bo_move_to_lru_tail);
  static void ttm_bo_bulk_move_helper(struct ttm_lru_bulk_move_pos *pos,
struct list_head *lru, bool is_swap)
  {
+   struct list_head *list;
LIST_HEAD(entries);
LIST_HEAD(before);
-   struct list_head *list1, *list2;
-   list1 = is_swap ? >last->swap : >last->lru;
-   list2 = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
+   reservation_object_assert_held(pos->last->resv);
+   list = is_swap ? >last->swap : >last->lru;
+   list_cut_position(, lru, list);
+
+   reservation_object_assert_held(pos->first->resv);
+   list = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
+   list_cut_position(, , list);

So the problem was that the first list_cut_position call could result in
list2 pointing to la-la-land? Good catch!

Yes, exactly. Thought that would be obvious, but going to add that
to the commit log.

Can I get a tested-by? You where much better at reproducing that than I'm.


Michel, Christian, thanks so much to take care of this when I was on
vacation. And sorry to let you take a long time for finding the cause.

Is that because I didn't hold the resveration before cut the list from
position "first" and "last"?


Yes, that was one problem. Another was that the cutting code was buggy 
and determined one of the positions to cut at the wrong time.



  May I know in which cases, we must hold the
bo's reservation firstly?


BOs are reserved to prevent moving them. E.g. when the BO isn't reserved 
it can move around and so the LRU where you want to add/remove it could 
change.


Christian.



Thanks,
Ray




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Re: [PATCH 1/3] drm/ttm: fix ttm_bo_bulk_move_helper

2018-09-06 Thread Huang Rui 
On Fri, Aug 31, 2018 at 05:17:33PM +0200, Christian König wrote:
> Am 31.08.2018 um 17:15 schrieb Michel Dänzer:
> >On 2018-08-31 3:10 p.m., Christian König wrote:
> >>Staring at the function for six hours, just to essentially move one line
> >>of code.
> >That sucks, but the commit log should describe what the problem was and
> >how this patch solves it.
> >
> >
> >>Signed-off-by: Christian König 
> >>---
> >>  drivers/gpu/drm/ttm/ttm_bo.c | 13 -
> >>  1 file changed, 8 insertions(+), 5 deletions(-)
> >>
> >>diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> >>index 35d53d81f486..138c98902033 100644
> >>--- a/drivers/gpu/drm/ttm/ttm_bo.c
> >>+++ b/drivers/gpu/drm/ttm/ttm_bo.c
> >>@@ -250,15 +250,18 @@ EXPORT_SYMBOL(ttm_bo_move_to_lru_tail);
> >>  static void ttm_bo_bulk_move_helper(struct ttm_lru_bulk_move_pos *pos,
> >>struct list_head *lru, bool is_swap)
> >>  {
> >>+   struct list_head *list;
> >>LIST_HEAD(entries);
> >>LIST_HEAD(before);
> >>-   struct list_head *list1, *list2;
> >>-   list1 = is_swap ? >last->swap : >last->lru;
> >>-   list2 = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
> >>+   reservation_object_assert_held(pos->last->resv);
> >>+   list = is_swap ? >last->swap : >last->lru;
> >>+   list_cut_position(, lru, list);
> >>+
> >>+   reservation_object_assert_held(pos->first->resv);
> >>+   list = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
> >>+   list_cut_position(, , list);
> >So the problem was that the first list_cut_position call could result in
> >list2 pointing to la-la-land? Good catch!
> 
> Yes, exactly. Thought that would be obvious, but going to add that
> to the commit log.
> 
> Can I get a tested-by? You where much better at reproducing that than I'm.
> 

Michel, Christian, thanks so much to take care of this when I was on
vacation. And sorry to let you take a long time for finding the cause.

Is that because I didn't hold the resveration before cut the list from
position "first" and "last"? May I know in which cases, we must hold the
bo's reservation firstly?

Thanks,
Ray


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Re: [PATCH 1/3] drm/ttm: fix ttm_bo_bulk_move_helper

2018-09-02 Thread Zhang, Jerry (Junwei) 

On 08/31/2018 09:10 PM, Christian König wrote:

Staring at the function for six hours, just to essentially move one line
of code.

Signed-off-by: Christian König 

Reviewed-by: Junwei Zhang 


---
  drivers/gpu/drm/ttm/ttm_bo.c | 13 -
  1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 35d53d81f486..138c98902033 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -250,15 +250,18 @@ EXPORT_SYMBOL(ttm_bo_move_to_lru_tail);
  static void ttm_bo_bulk_move_helper(struct ttm_lru_bulk_move_pos *pos,
struct list_head *lru, bool is_swap)
  {
+   struct list_head *list;
LIST_HEAD(entries);
LIST_HEAD(before);
-   struct list_head *list1, *list2;

-   list1 = is_swap ? >last->swap : >last->lru;
-   list2 = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
+   reservation_object_assert_held(pos->last->resv);
+   list = is_swap ? >last->swap : >last->lru;
+   list_cut_position(, lru, list);
+
+   reservation_object_assert_held(pos->first->resv);
+   list = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
+   list_cut_position(, , list);

-   list_cut_position(, lru, list1);
-   list_cut_position(, , list2);
list_splice(, lru);
list_splice_tail(, lru);
  }


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Re: [PATCH 1/3] drm/ttm: fix ttm_bo_bulk_move_helper

2018-08-31 Thread Christian König 

Am 31.08.2018 um 17:15 schrieb Michel Dänzer:

On 2018-08-31 3:10 p.m., Christian König wrote:

Staring at the function for six hours, just to essentially move one line
of code.

That sucks, but the commit log should describe what the problem was and
how this patch solves it.



Signed-off-by: Christian König 
---
  drivers/gpu/drm/ttm/ttm_bo.c | 13 -
  1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 35d53d81f486..138c98902033 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -250,15 +250,18 @@ EXPORT_SYMBOL(ttm_bo_move_to_lru_tail);
  static void ttm_bo_bulk_move_helper(struct ttm_lru_bulk_move_pos *pos,
struct list_head *lru, bool is_swap)
  {
+   struct list_head *list;
LIST_HEAD(entries);
LIST_HEAD(before);
-   struct list_head *list1, *list2;
  
-	list1 = is_swap ? >last->swap : >last->lru;

-   list2 = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
+   reservation_object_assert_held(pos->last->resv);
+   list = is_swap ? >last->swap : >last->lru;
+   list_cut_position(, lru, list);
+
+   reservation_object_assert_held(pos->first->resv);
+   list = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
+   list_cut_position(, , list);

So the problem was that the first list_cut_position call could result in
list2 pointing to la-la-land? Good catch!


Yes, exactly. Thought that would be obvious, but going to add that to 
the commit log.


Can I get a tested-by? You where much better at reproducing that than I'm.

Christian.
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Re: [PATCH 1/3] drm/ttm: fix ttm_bo_bulk_move_helper

2018-08-31 Thread Michel Dänzer 
On 2018-08-31 3:10 p.m., Christian König wrote:
> Staring at the function for six hours, just to essentially move one line
> of code.

That sucks, but the commit log should describe what the problem was and
how this patch solves it.


> Signed-off-by: Christian König 
> ---
>  drivers/gpu/drm/ttm/ttm_bo.c | 13 -
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index 35d53d81f486..138c98902033 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -250,15 +250,18 @@ EXPORT_SYMBOL(ttm_bo_move_to_lru_tail);
>  static void ttm_bo_bulk_move_helper(struct ttm_lru_bulk_move_pos *pos,
>   struct list_head *lru, bool is_swap)
>  {
> + struct list_head *list;
>   LIST_HEAD(entries);
>   LIST_HEAD(before);
> - struct list_head *list1, *list2;
>  
> - list1 = is_swap ? >last->swap : >last->lru;
> - list2 = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
> + reservation_object_assert_held(pos->last->resv);
> + list = is_swap ? >last->swap : >last->lru;
> + list_cut_position(, lru, list);
> +
> + reservation_object_assert_held(pos->first->resv);
> + list = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
> + list_cut_position(, , list);

So the problem was that the first list_cut_position call could result in
list2 pointing to la-la-land? Good catch!


-- 
Earthling Michel Dänzer   |   http://www.amd.com
Libre software enthusiast | Mesa and X developer
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