From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout-02.galae.net (smtpout-02.galae.net [185.246.84.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4D4A72459F7 for ; Fri, 26 Sep 2025 16:00:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.246.84.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758902461; cv=none; b=BBLHmrKchLw8tQnrFbr7AWQuSeTG0R/Q+OO2KatSwm3Uwqsm9X0+wpo7Oy5WE3shcjswGQbuRHrbhHoxpiR8RsKuTpHcG/LM81W4h87r8+2ngDoS2yMNbdrD5aKQFPEiuM6WOjosDfJjJpF2g+Dk/YwjCbKQXmX3B5KhiLlaMyg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758902461; c=relaxed/simple; bh=+Y2++zYj21q+KEWiAsSAEfIpc1oJGQSTIPtdn+yg2B8=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=sN5i0WIFILbaaqXJtxGBokhXP4xPlL2Wq0Xk7mLNfx+o7tf2jyj/ZWZUiKv0MHGHUKZ2ZNxcd8j0RrOvcTGNTD5HBY4JXcaoNzoo1jNVhug3Bda/jYR7WF/QUgkv6B0TM4iu0RnvD4zq/iAWzeGgGaujZBtaKn0Lt1sYFcVSmYI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=DguTKvKv; arc=none smtp.client-ip=185.246.84.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="DguTKvKv" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-02.galae.net (Postfix) with ESMTPS id E86EF1A0FEC; Fri, 26 Sep 2025 16:00:57 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id BE9EA606B5; Fri, 26 Sep 2025 16:00:57 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 0EC8A102F1980; Fri, 26 Sep 2025 18:00:54 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1758902457; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=t4G6wBu8UnoC2aStDYzdldOpdl6B8KUtUfr4tyax8QI=; b=DguTKvKvD//rLvhdqb0VJLcKWpgyEcp+48rm/D8nvSYb1kmBl1EjrXCdrkKf9YL2DrfqV6 gPebDaCppZ8wPDOFsqE1y1lW6cT0JaaR97O/xCHvi8xcoIvDasCfDROpNAl5SDVyAmtDwl vECj0ZbJFiEgx681THe+2xP1o8IT0cWNhplUQecDLpzJj6Pocu6Ye3D6/pffPlzO8pw25u /aWZkuE5LVB9ismDQRJBLgZtzAXtGG5dyGX7AKslHZ/O/84aGb+Fdf0YdjCeRxCr/EnmTm Zb5bhYCBVdxAs875B3Wnt7ef0+RtRm85I4D5KGd4qM07Nj6W6Ry5NlCujspu0A== From: Luca Ceresoli Date: Fri, 26 Sep 2025 17:59:48 +0200 Subject: [PATCH 7/7] drm/bridge: prevent encoder chain changes while iterating in drm_atomic_bridge_chain_post_disable/pre_enable() Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20250926-drm-bridge-alloc-encoder-chain-mutex-v1-7-23b62c47356a@bootlin.com> References: <20250926-drm-bridge-alloc-encoder-chain-mutex-v1-0-23b62c47356a@bootlin.com> In-Reply-To: <20250926-drm-bridge-alloc-encoder-chain-mutex-v1-0-23b62c47356a@bootlin.com> To: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec Cc: Hui Pu , Thomas Petazzoni , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Luca Ceresoli X-Mailer: b4 0.14.2 X-Last-TLS-Session-Version: TLSv1.3 Take the encoder chain mutex while iterating over the encoder chain in drm_atomic_bridge_chain_pre_enable() and drm_atomic_bridge_chain_post-disable(). These functions have nested list_for_each_*() loops, which makes them complicated. list_for_each_entry_from() loops could be replaced by drm_for_each_bridge_in_chain_from(), but it would not work in a nested way. Besides, there is no "_reverse" variant of drm_for_each_bridge_in_chain_from(). Keep code simple and readable by explicitly locking around the outer loop. Thankfully there are no return points inside the loops, so the change is trivial and readable. Signed-off-by: Luca Ceresoli --- drivers/gpu/drm/drm_bridge.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c index 66c0a80db8426ffb360248895cfe2a11d6007ed7..00e0a88128d0eeabf25911591ad8c482d6c1caf8 100644 --- a/drivers/gpu/drm/drm_bridge.c +++ b/drivers/gpu/drm/drm_bridge.c @@ -765,6 +765,7 @@ void drm_atomic_bridge_chain_post_disable(struct drm_bridge *bridge, encoder = bridge->encoder; + drm_encoder_chain_lock(encoder); list_for_each_entry_from(bridge, &encoder->bridge_chain, chain_node) { limit = NULL; @@ -813,6 +814,7 @@ void drm_atomic_bridge_chain_post_disable(struct drm_bridge *bridge, /* Jump all bridges that we have already post_disabled */ bridge = limit; } + drm_encoder_chain_unlock(encoder); } EXPORT_SYMBOL(drm_atomic_bridge_chain_post_disable); @@ -859,6 +861,7 @@ void drm_atomic_bridge_chain_pre_enable(struct drm_bridge *bridge, encoder = bridge->encoder; + drm_encoder_chain_lock(encoder); list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) { if (iter->pre_enable_prev_first) { next = iter; @@ -901,6 +904,7 @@ void drm_atomic_bridge_chain_pre_enable(struct drm_bridge *bridge, if (iter == bridge) break; } + drm_encoder_chain_unlock(encoder); } EXPORT_SYMBOL(drm_atomic_bridge_chain_pre_enable); -- 2.51.0