From nobody Thu Apr 2 23:31:26 2026 Received: from smtpout-04.galae.net (smtpout-04.galae.net [185.171.202.116]) (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 0F5D23D8132 for ; Tue, 24 Mar 2026 08:58:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.171.202.116 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774342716; cv=none; b=ftVx82Lcq9i6k0fwjGRdW643IGCq5aBznpx36JuYGtKl/WE+hZmEfT81go8ukB9Cy6y1HNB8WJOw1Kr781qBbGaxp2u+bxoxJC94sbZOyP/mR5DnPGoyV2hxh03Dv80d1WxuTPl6AYqKAWbT96Yar5hTvXsomS6eYqnbEXjYCGM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774342716; c=relaxed/simple; bh=NXDi1bIBY0bfZZ9JMkXcDgOIGqVyd+NtlhlbI3nMbGg=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=EFyESVs9XLa0Yscq7CUAN5RbxNar/qA2hUin7XpqmqloJp2j77SRnGkw+sWQITEBUQSE6zY6WRxvpqbv6V4WXO0sQRCNR7w6YsMfVyotbPaNR6TJt8+ocFyn51yR8LXmAxneFROXM6Rl7qu+pTHFQQJ2QhA9x8BGwsxmGVE3JWQ= 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=k6uW2/ZG; arc=none smtp.client-ip=185.171.202.116 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="k6uW2/ZG" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-04.galae.net (Postfix) with ESMTPS id D2B5EC58095; Tue, 24 Mar 2026 08:59:00 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id A23BB6011D; Tue, 24 Mar 2026 08:58:33 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 8536E10450F8E; Tue, 24 Mar 2026 09:58:29 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1774342712; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=2dUn42zD2E9NQa8EnfP56hhRdT/h4FqbY5w3v4OIxuc=; b=k6uW2/ZGLM5rV3ms+nU0LEbdm86usDQAl1wXD7nBjHiSboqEq131NI+ns0czp9D4E7RSZc u9Cqx6WfojEHXGGWCjIr8p5pCr+2OE4pqr7WLyYmtnIa0JwqcKTtUPPCqympm5vst8Z1/l QMcwZzBY8NvoAAX2ZqbxysRMj2APScDdBBCj38nYtcFNuXLidwWR1y52Pe0VB5VKTfaMVO RPZe6Kwom8RZvkBz18Igsi9e3RhqhdVqqg3IMIidJyK6Anr9JkzJ9Yzk+TB3EguGfP4MYa ZbkdosBCzQ7+mspjrRbT6aH4UdvxiVKHh9L+zt7PWM/lUi0B20J2vEoZBaXOHA== From: Luca Ceresoli Date: Tue, 24 Mar 2026 09:58:10 +0100 Subject: [PATCH v5 3/7] drm/bridge: drm_bridge_attach: lock the encoder chain mutex during insertion 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: quoted-printable Message-Id: <20260324-drm-bridge-alloc-encoder-chain-mutex-v5-3-8bf786c5c7e6@bootlin.com> References: <20260324-drm-bridge-alloc-encoder-chain-mutex-v5-0-8bf786c5c7e6@bootlin.com> In-Reply-To: <20260324-drm-bridge-alloc-encoder-chain-mutex-v5-0-8bf786c5c7e6@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, Ian Ray , Luca Ceresoli X-Mailer: b4 0.14.3 X-Last-TLS-Session-Version: TLSv1.3 drm_bridge_attach() modifies the encoder bridge chain, so take a mutex around such operations to allow users of the chain to protect themselves from chain modifications while iterating. Reviewed-by: Maxime Ripard Signed-off-by: Luca Ceresoli --- Changes in v3: - Lock encoder->bridge_chain_mutex directly, no wrappers Changes in v2: - Removed comment before on drm_bridge_detach() --- 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 30d957675d87..42ca4b243579 100644 --- a/drivers/gpu/drm/drm_bridge.c +++ b/drivers/gpu/drm/drm_bridge.c @@ -574,10 +574,12 @@ int drm_bridge_attach(struct drm_encoder *encoder, st= ruct drm_bridge *bridge, bridge->dev =3D encoder->dev; bridge->encoder =3D encoder; =20 + mutex_lock(&encoder->bridge_chain_mutex); if (previous) list_add(&bridge->chain_node, &previous->chain_node); else list_add(&bridge->chain_node, &encoder->bridge_chain); + mutex_unlock(&encoder->bridge_chain_mutex); =20 if (bridge->funcs->attach) { ret =3D bridge->funcs->attach(bridge, encoder, flags); @@ -594,7 +596,9 @@ int drm_bridge_attach(struct drm_encoder *encoder, stru= ct drm_bridge *bridge, err_reset_bridge: bridge->dev =3D NULL; bridge->encoder =3D NULL; + mutex_lock(&encoder->bridge_chain_mutex); list_del(&bridge->chain_node); + mutex_unlock(&encoder->bridge_chain_mutex); =20 if (ret !=3D -EPROBE_DEFER) DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n", --=20 2.53.0