Re: [PATCH] drm/ttm: fix error handling in ttm_bo_handle_move_mem()

[Christian König]

Am 16.06.21 um 10:37 schrieb Dan Carpenter:
> On Wed, Jun 16, 2021 at 08:46:33AM +0200, Christian König wrote:
> > Sending the first message didn't worked, so let's try again.
> >
> > Am 16.06.21 um 08:30 schrieb Dan Carpenter:
> > > There are three bugs here:
> > > 1) We need to call unpopulate() if ttm_tt_populate() succeeds.
> > > 2) The "new_man = ttm_manager_type(bdev, bo->mem.mem_type);" assignment
> > >      was wrong and it was really assigning "new_mem = old_mem;".  There
> > >      is no need for this assignment anyway as we already have the value
> > >      for "new_mem".
> > > 3) The (!new_man->use_tt) condition is reversed.
> > >
> > > Fixes: ba4e7d973dd0 ("drm: Add the TTM GPU memory manager subsystem.")
> > > Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> > > ---
> > > This is from reading the code and I can't swear that I have understood
> > > it correctly.  My nouveau driver is currently unusable and this patch
> > > has not helped.  But hopefully if I fix enough bugs eventually it will
> > > start to work.
> > Well NAK, the code previously looked quite well and you are breaking it now.
> >
> > What's the problem with nouveau?
> The new Firefox seems to excersize nouveau more than the old one so
> when I start 10 firefox windows it just hangs the graphics.
>
> I've added debug code and it seems like the problem is that
> nv50_mem_new() is failing.

Sounds like it is running out of memory to me.

Do you have a dmesg?

> > >    drivers/gpu/drm/ttm/ttm_bo.c | 14 ++++++++------
> > >    1 file changed, 8 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> > > index ebcffe794adb..72dde093f754 100644
> > > --- a/drivers/gpu/drm/ttm/ttm_bo.c
> > > +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> > > @@ -180,12 +180,12 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
> > >    		 */
> > >    		ret = ttm_tt_create(bo, old_man->use_tt);
> > >    		if (ret)
> > > -			goto out_err;
> > > +			return ret;
> > >    		if (mem->mem_type != TTM_PL_SYSTEM) {
> > >    			ret = ttm_tt_populate(bo->bdev, bo->ttm, ctx);
> > >    			if (ret)
> > > -				goto out_err;
> > > +				goto err_destroy;
> > >    		}
> > >    	}
> > > @@ -193,15 +193,17 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
> > >    	if (ret) {
> > >    		if (ret == -EMULTIHOP)
> > >    			return ret;
> > > -		goto out_err;
> > > +		goto err_unpopulate;
> > >    	}
> > >    	ctx->bytes_moved += bo->base.size;
> > >    	return 0;
> > > -out_err:
> > > -	new_man = ttm_manager_type(bdev, bo->mem.mem_type);
> > This here switches new and old manager. E.g. the new_man is now pointing to
> > the existing resource manager.
> Why not just use "old_man" instead of basically the equivalent to
> "new_man = old_man"?  Can the old_man change part way through the
> function?

Good question :)

I don't think that old_man could change and yes that would be much more 
easier to understand.

Regards,
Christian.

> regards,
> dan carpenter