From 648a0dc0d78c369233b16878e4f351efe7fd8df6 Mon Sep 17 00:00:00 2001 From: "Jesse.Zhang" Date: Fri, 9 May 2025 17:18:16 +0800 Subject: [PATCH 3627/5403] drm/amdgpu: Fix user queue deadlock by reordering mutex locking MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This resolves a deadlock between user queue management and GPU reset paths by enforcing consistent lock ordering. The deadlock occurred when: 1. Process exit path (amdgpu_userq_mgr_fini) would: - Take uqm->userq_mutex - Then try to take adev->userq_mutex for list operations 2. GPU reset path (amdgpu_userq_pre_reset) would: - Take adev->userq_mutex first (for list traversal) - Then take uqm->userq_mutex The solution establishes a strict top-down locking order: 1. Always take adev->userq_mutex before any uqm->userq_mutex 2. Maintain this order consistently across all code paths Changes made: - Reordered locking in amdgpu_userq_mgr_fini() to take device lock first - Kept existing proper order in amdgpu_userq_pre_reset() - Simplified the fini flow by removing redundant operations This prevents circular dependencies while maintaining thread safety during both normal operation and GPU reset scenarios. Fixes: 4ce60dbada96 ("drm/amdgpu: store userq_managers in a list in adev") Reviewed-by: Christian König Reviewed-by: Arvind Yadav Signed-off-by: Jesse Zhang Signed-off-by: Alex Deucher --- drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c index ac3ab4cc8e5a..9d1f185a815e 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c @@ -779,22 +779,23 @@ void amdgpu_userq_mgr_fini(struct amdgpu_userq_mgr *userq_mgr) cancel_delayed_work_sync(&userq_mgr->resume_work); + mutex_lock(&adev->userq_mutex); mutex_lock(&userq_mgr->userq_mutex); idr_for_each_entry(&userq_mgr->userq_idr, queue, queue_id) { amdgpu_userq_wait_for_last_fence(userq_mgr, queue); amdgpu_userq_unmap_helper(userq_mgr, queue); amdgpu_userq_cleanup(userq_mgr, queue, queue_id); } - mutex_lock(&adev->userq_mutex); + list_for_each_entry_safe(uqm, tmp, &adev->userq_mgr_list, list) { if (uqm == userq_mgr) { list_del(&uqm->list); break; } } - mutex_unlock(&adev->userq_mutex); idr_destroy(&userq_mgr->userq_idr); mutex_unlock(&userq_mgr->userq_mutex); + mutex_unlock(&adev->userq_mutex); mutex_destroy(&userq_mgr->userq_mutex); } -- 2.54.0