Am 11.02.20 um 16:02 schrieb Pan, Xinhui:
2020年2月11日 22:14，Daniel Vetter daniel@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@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.
Yeah that summarize my recent presentation about TTM pretty much :)
Double checked that and the only reason we have the lock is that in ttm_mem_evict_first() we trylock first and then grab a reference.
So we should probably rework that code as well and then we can also drop that lock here, but that should come later.
Christian.
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;-- 2.17.1
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-- Daniel Vetter Software Engineer, Intel Corporation https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fblog.ffwll....