The patch below does not apply to the 6.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.
To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y git checkout FETCH_HEAD git cherry-pick -x b2ed01e7ad3de80333e9b962a44024b094bc0b2b # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<[email protected]>' --in-reply-to '2026052035-sweat-creed-1388@gregkh' --subject-prefix 'PATCH 6.18.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From b2ed01e7ad3de80333e9b962a44024b094bc0b2b Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= <[email protected]> Date: Tue, 28 Apr 2026 11:44:42 +0200 Subject: [PATCH] drm/ttm: Fix ttm_bo_swapout() infinite LRU walk on swapout failure MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When ttm_tt_swapout() fails, the current code calls ttm_resource_add_bulk_move() followed by ttm_resource_move_to_lru_tail() to restore the resource's bulk_move membership. However, ttm_resource_move_to_lru_tail() places the resource at the tail of the LRU list which, relative to the walk cursor's hitch node (placed immediately after the resource when it was yielded), puts the resource *in front of the* the hitch. The next list_for_each_entry_continue() from the hitch finds the same resource again, causing an infinite loop. Fix by deferring del_bulk_move to the success path only. On the success path, TTM_TT_FLAG_SWAPPED has just been set by ttm_tt_swapout() but the resource is still tracked in the bulk_move range, so ttm_resource_del_bulk_move()'s !ttm_resource_unevictable() guard would incorrectly skip the removal. Introduce ttm_resource_del_bulk_move_unevictable() which bypasses that guard. Reported-by: Jatin Kataria <[email protected]> Fixes: fc5d96670eb2 ("drm/ttm: Move swapped objects off the manager's LRU list") Cc: Christian König <[email protected]> Cc: Matthew Brost <[email protected]> Cc: <[email protected]> Cc: <[email protected]> # v6.13+ Assisted-by: GitHub_Copilot:claude-sonnet-4.6 Signed-off-by: Thomas Hellström <[email protected]> Reviewed-by: Christian König <[email protected]> Tested-by: Boqun Feng <[email protected]> Link: https://patch.msgid.link/[email protected] diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index d85f0a37ac35..293401705542 100644 --- a/drivers/gpu/drm/ttm/ttm_bo.c +++ b/drivers/gpu/drm/ttm/ttm_bo.c @@ -1177,17 +1177,13 @@ ttm_bo_swapout_cb(struct ttm_lru_walk *walk, struct ttm_buffer_object *bo) bdev->funcs->swap_notify(bo); if (ttm_tt_is_populated(tt)) { - spin_lock(&bdev->lru_lock); - ttm_resource_del_bulk_move(bo->resource, bo); - spin_unlock(&bdev->lru_lock); - ret = ttm_tt_swapout(bdev, tt, swapout_walk->gfp_flags); - - spin_lock(&bdev->lru_lock); - if (ret) - ttm_resource_add_bulk_move(bo->resource, bo); - ttm_resource_move_to_lru_tail(bo->resource); - spin_unlock(&bdev->lru_lock); + if (!ret) { + spin_lock(&bdev->lru_lock); + ttm_resource_del_bulk_move_unevictable(bo->resource, bo); + ttm_resource_move_to_lru_tail(bo->resource); + spin_unlock(&bdev->lru_lock); + } } out: diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c index 9f36631d48b6..0e5f1582f13d 100644 --- a/drivers/gpu/drm/ttm/ttm_resource.c +++ b/drivers/gpu/drm/ttm/ttm_resource.c @@ -292,6 +292,19 @@ void ttm_resource_del_bulk_move(struct ttm_resource *res, ttm_lru_bulk_move_del(bo->bulk_move, res); } +/* + * Remove a resource from its bulk_move, bypassing the unevictable check. + * Use only when the resource is known to still be tracked in the range despite + * the BO having just become unevictable; asserts that this is the case. + */ +void ttm_resource_del_bulk_move_unevictable(struct ttm_resource *res, + struct ttm_buffer_object *bo) +{ + WARN_ON_ONCE(!ttm_resource_unevictable(res, bo)); + if (bo->bulk_move) + ttm_lru_bulk_move_del(bo->bulk_move, res); +} + /* Move a resource to the LRU or bulk tail */ void ttm_resource_move_to_lru_tail(struct ttm_resource *res) { diff --git a/include/drm/ttm/ttm_resource.h b/include/drm/ttm/ttm_resource.h index 33e80f30b8b8..a5d386583fb6 100644 --- a/include/drm/ttm/ttm_resource.h +++ b/include/drm/ttm/ttm_resource.h @@ -448,6 +448,8 @@ void ttm_resource_add_bulk_move(struct ttm_resource *res, struct ttm_buffer_object *bo); void ttm_resource_del_bulk_move(struct ttm_resource *res, struct ttm_buffer_object *bo); +void ttm_resource_del_bulk_move_unevictable(struct ttm_resource *res, + struct ttm_buffer_object *bo); void ttm_resource_move_to_lru_tail(struct ttm_resource *res); void ttm_resource_init(struct ttm_buffer_object *bo,
