From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1934AC52D71 for ; Wed, 7 Aug 2024 14:37:42 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7D09710E54C; Wed, 7 Aug 2024 14:37:41 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="DzMGoa4D"; dkim-atps=neutral Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by gabe.freedesktop.org (Postfix) with ESMTPS id 9372410E54C for ; Wed, 7 Aug 2024 14:37:40 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id F0B9B61028; Wed, 7 Aug 2024 14:37:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 51EF9C32781; Wed, 7 Aug 2024 14:37:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1723041459; bh=w9q7N/cXR+ywf2V7kYelGMsCJzGN8TZ3szWi+dSVpNY=; h=Subject:To:Cc:From:Date:From; b=DzMGoa4DuOKFAd3Xpf3JPr/gMAdhbAI9Spnk4Lu2Udn0hVVa1TVdu71GKAmaBEvEr C+4zKRSgS4XHp7cNYqhtHgwzmtsvHOenyoWMEv1Wd6VTyCBPcIQK0R2EVTRqdIE1g9 LyRbPHcEHuzSRl8SkNQ/9PXssCbqLVUlJLk90up8= Subject: Patch "drm/vmwgfx: Fix a deadlock in dma buf fence polling" has been added to the 6.6-stable tree To: bcm-kernel-feedback-list@broadcom.com, dri-devel@lists.freedesktop.org, gregkh@linuxfoundation.org, maaz.mombasawala@broadcom.com, martin.krastev@broadcom.com, zack.rusin@broadcom.com Cc: From: Date: Wed, 07 Aug 2024 16:35:58 +0200 Message-ID: <2024080758-snowbound-ditzy-18cf@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit X-stable: commit X-Patchwork-Hint: ignore X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" This is a note to let you know that I've just added the patch titled drm/vmwgfx: Fix a deadlock in dma buf fence polling to the 6.6-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: drm-vmwgfx-fix-a-deadlock-in-dma-buf-fence-polling.patch and it can be found in the queue-6.6 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >From e58337100721f3cc0c7424a18730e4f39844934f Mon Sep 17 00:00:00 2001 From: Zack Rusin Date: Mon, 22 Jul 2024 14:41:13 -0400 Subject: drm/vmwgfx: Fix a deadlock in dma buf fence polling From: Zack Rusin commit e58337100721f3cc0c7424a18730e4f39844934f upstream. Introduce a version of the fence ops that on release doesn't remove the fence from the pending list, and thus doesn't require a lock to fix poll->fence wait->fence unref deadlocks. vmwgfx overwrites the wait callback to iterate over the list of all fences and update their status, to do that it holds a lock to prevent the list modifcations from other threads. The fence destroy callback both deletes the fence and removes it from the list of pending fences, for which it holds a lock. dma buf polling cb unrefs a fence after it's been signaled: so the poll calls the wait, which signals the fences, which are being destroyed. The destruction tries to acquire the lock on the pending fences list which it can never get because it's held by the wait from which it was called. Old bug, but not a lot of userspace apps were using dma-buf polling interfaces. Fix those, in particular this fixes KDE stalls/deadlock. Signed-off-by: Zack Rusin Fixes: 2298e804e96e ("drm/vmwgfx: rework to new fence interface, v2") Cc: Broadcom internal kernel review list Cc: dri-devel@lists.freedesktop.org Cc: # v6.2+ Reviewed-by: Maaz Mombasawala Reviewed-by: Martin Krastev Link: https://patchwork.freedesktop.org/patch/msgid/20240722184313.181318-2-zack.rusin@broadcom.com Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/vmwgfx/vmwgfx_fence.c | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) --- a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c @@ -32,7 +32,6 @@ #define VMW_FENCE_WRAP (1 << 31) struct vmw_fence_manager { - int num_fence_objects; struct vmw_private *dev_priv; spinlock_t lock; struct list_head fence_list; @@ -124,13 +123,13 @@ static void vmw_fence_obj_destroy(struct { struct vmw_fence_obj *fence = container_of(f, struct vmw_fence_obj, base); - struct vmw_fence_manager *fman = fman_from_fence(fence); - spin_lock(&fman->lock); - list_del_init(&fence->head); - --fman->num_fence_objects; - spin_unlock(&fman->lock); + if (!list_empty(&fence->head)) { + spin_lock(&fman->lock); + list_del_init(&fence->head); + spin_unlock(&fman->lock); + } fence->destroy(fence); } @@ -257,7 +256,6 @@ static const struct dma_fence_ops vmw_fe .release = vmw_fence_obj_destroy, }; - /* * Execute signal actions on fences recently signaled. * This is done from a workqueue so we don't have to execute @@ -355,7 +353,6 @@ static int vmw_fence_obj_init(struct vmw goto out_unlock; } list_add_tail(&fence->head, &fman->fence_list); - ++fman->num_fence_objects; out_unlock: spin_unlock(&fman->lock); @@ -403,7 +400,7 @@ static bool vmw_fence_goal_new_locked(st u32 passed_seqno) { u32 goal_seqno; - struct vmw_fence_obj *fence; + struct vmw_fence_obj *fence, *next_fence; if (likely(!fman->seqno_valid)) return false; @@ -413,7 +410,7 @@ static bool vmw_fence_goal_new_locked(st return false; fman->seqno_valid = false; - list_for_each_entry(fence, &fman->fence_list, head) { + list_for_each_entry_safe(fence, next_fence, &fman->fence_list, head) { if (!list_empty(&fence->seq_passed_actions)) { fman->seqno_valid = true; vmw_fence_goal_write(fman->dev_priv, Patches currently in stable-queue which might be from zack.rusin@broadcom.com are queue-6.6/drm-vmwgfx-trigger-a-modeset-when-the-screen-moves.patch queue-6.6/drm-vmwgfx-fix-a-deadlock-in-dma-buf-fence-polling.patch queue-6.6/drm-vmwgfx-fix-overlay-when-using-screen-targets.patch