[PATCH 5/6] drm/ttm: replace dma_resv object on deleted BOs v2

[Pan, Xinhui]

> 2020年2月11日 22:14，Daniel Vetter <daniel at ffwll.ch> 写道：
> 
> On Mon, Feb 10, 2020 at 04:09:06PM +0100, Christian König wrote:
>> When non-imported BOs are resurrected for delayed delete we replace
>> the dma_resv object to allow for easy reclaiming of the resources.
>> 
>> v2: move that to ttm_bo_individualize_resv
>> 
>> Signed-off-by: Christian König <christian.koenig at amd.com>
>> ---
>> drivers/gpu/drm/ttm/ttm_bo.c | 10 +++++++++-
>> 1 file changed, 9 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
>> index d0624685f5d2..4d161038de98 100644
>> --- a/drivers/gpu/drm/ttm/ttm_bo.c
>> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
>> @@ -393,6 +393,14 @@ static int ttm_bo_individualize_resv(struct ttm_buffer_object *bo)
>> 
>> 	r = dma_resv_copy_fences(&bo->base._resv, bo->base.resv);
>> 	dma_resv_unlock(&bo->base._resv);
>> +	if (r)
>> +		return r;
>> +
>> +	if (bo->type != ttm_bo_type_sg) {
>> +		spin_lock(&ttm_bo_glob.lru_lock);
>> +		bo->base.resv = &bo->base._resv;
> 
> Having the dma_resv pointer be protected by the lru_lock for ttm internal
> stuff, but invariant everywhere else is really confusing. Not sure that's

I think this is reader VS writer.
To avoid any internal functions using the old resv,  using an existing spin lock is acceptable.
Maybe RCU is better? That will need a lot of effort.
Anyway, ttm sucks. We HAS done a lot of work on it to make it better running on modern system.


> a great idea, I've just chased some ttm code around freaking out about
> that.
> -Daniel
> 
>> +		spin_unlock(&ttm_bo_glob.lru_lock);
>> +	}
>> 
>> 	return r;
>> }
>> @@ -720,7 +728,7 @@ static bool ttm_bo_evict_swapout_allowable(struct ttm_buffer_object *bo,
>> 
>> 	if (bo->base.resv == ctx->resv) {
>> 		dma_resv_assert_held(bo->base.resv);
>> -		if (ctx->flags & TTM_OPT_FLAG_ALLOW_RES_EVICT || bo->deleted)
>> +		if (ctx->flags & TTM_OPT_FLAG_ALLOW_RES_EVICT)
>> 			ret = true;
>> 		*locked = false;
>> 		if (busy)
>> -- 
>> 2.17.1
>> 
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel at lists.freedesktop.org
>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.freedesktop.org%2Fmailman%2Flistinfo%2Fdri-devel&data=02%7C01%7CXinhui.Pan%40amd.com%7Cee67310e26b64ca9e79008d7aefca7b4%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637170272481765904&sdata=ZpnP9MNBP1csQCKPR275ejIvsZ3b8xL80tmSlpf7MPA%3D&reserved=0
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fblog.ffwll.ch&data=02%7C01%7CXinhui.Pan%40amd.com%7Cee67310e26b64ca9e79008d7aefca7b4%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637170272481765904&sdata=fk28jtHhAnE312CFMgVXaZtaS2YNqJjmyJ317FWjAoM%3D&reserved=0