Re: [Intel-gfx] [PATCH 3/4] drm/ttm: Don't leak a resource on eviction error

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On 6/22/23 16:48, Christian König wrote:


Am 22.06.23 um 16:08 schrieb Thomas Hellström:

On 6/22/23 15:55, Andi Shyti wrote:
Hi Thomas,

On Thu, Jun 22, 2023 at 12:14:11PM +0200, Thomas Hellström wrote:
On eviction errors other than -EMULTIHOP we were leaking a resource.
Fix.

Fixes: 403797925768 ("drm/ttm: Fix multihop assert on eviction.")
Cc: Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>
Cc: Christian König <christian.koenig@xxxxxxx>
Cc: Christian Koenig <christian.koenig@xxxxxxx>
Cc: Huang Rui <ray.huang@xxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx> # v5.15+
Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
---
  drivers/gpu/drm/ttm/ttm_bo.c | 16 ++++++++--------
  1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 615d30c4262d..89530f2a027f 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -462,14 +462,14 @@ static int ttm_bo_evict(struct ttm_buffer_object *bo,
      ret = ttm_bo_handle_move_mem(bo, evict_mem, true, ctx, &hop);
      if (ret == -EMULTIHOP) {
          ret = ttm_bo_bounce_temp_buffer(bo, &evict_mem, ctx, &hop);
-        if (ret) {
-            if (ret != -ERESTARTSYS && ret != -EINTR)
-                pr_err("Buffer eviction failed\n");
-            ttm_resource_free(bo, &evict_mem);
-            goto out;
-        }
-        /* try and move to final place now. */
-        goto bounce;
+        if (!ret)
+            /* try and move to final place now. */
+            goto bounce;
As we are at this, can't we replace this with a while()? Goto's
used instead of a while loop are a fist in the eye...

I'm completely OK with that. this patch already did away with one of them. Let's hear Christian's opinion first, though.

I'm not a fan of that goto either, but could we somehow avoid the while(1) ? E.g. something like do { } while (!ret) after handling the multihop?

I think the construct that makes it most obvious what's happening, although it needs two tests for -EMULTIHOP is something like

do {
....
   if (ret != -EMULTIHOP)
      break;
   ....
} while (ret ==-EMULTIHOP);

Will be out tomorrow, though, so I don't have time to respin before Monday.

/Thomas



Christian.


Thanks,

Thomas






It looks even better:

    while (1) {
        ret = ttm_bo_handle_move_mem(bo, evict_mem, true, ctx, &hop);
        if (!ret)
            break;

        if (ret == -EMULTIHOP)
            ret = ttm_bo_bounce_temp_buffer(bo, &evict_mem,
                            ctx, &hop);

        /* try again */
        if (!ret)
            continue;

        ttm_resource_free(bo, &evict_mem);
        if (ret != -ERESTARTSYS && ret != -EINTR)
            pr_err("Buffer eviction failed\n");

        break;
    }

Andi

+    }
+    if (ret) {
+        ttm_resource_free(bo, &evict_mem);
+        if (ret != -ERESTARTSYS && ret != -EINTR)
+            pr_err("Buffer eviction failed\n");
      }
  out:
      return ret;
--
2.40.1




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