From nobody Thu Dec 18 04:58:00 2025 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 2D01B358D01 for ; Tue, 11 Nov 2025 12:01:41 +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=1762862504; cv=none; b=uhjb61HGXkZP83ocwyjYW9wRDVgLw5xvqUWPgirLbENj3FzjBJFn4cj+UBKXSK0OUvVZZhF0z0eS+lvnjBAbBB8a/Sk+8HtAEL7H45oFuDieXVpOftueGutx1SCe9zqmCzwVcMjx1DpY4R3dD2ogItJ4zD7c4YwMu3kecj1C5CI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762862504; c=relaxed/simple; bh=1clLNtEjwoVOKR5NKC+W2AEfzxwh8weW58OA/GwlBLU=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=H1QFhnSnq5XuCI6BEUS8W/opKBjW8so/E/LmAn44lDT6XrGTS0+zytE/XrWb06xbEyt1Jdnl1BYsIUQSiSD7WnoUFuzFMPVvkAQ52UzM+tIuWXzVO8PgxrDmj8UmQqNP2b5Oes7/CBA2+54DlsBhQbtQlpQ54Slt5Y71BB2z3sE= 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=h+GBEUer; 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="h+GBEUer" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-04.galae.net (Postfix) with ESMTPS id D3440C0F547; Tue, 11 Nov 2025 12:01:13 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id 5EDEF606FB; Tue, 11 Nov 2025 12:01:35 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 885C110371757; Tue, 11 Nov 2025 13:01:32 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1762862494; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=TA4TZzdHdTlEwf3ZFsWUEX0NQNey9iL6sbyvv48f/cQ=; b=h+GBEUer8cMBIfQmoPpCeJekDGUYKE98C+sDX0n5/CZ94fy/iFSBaQbvTa0WJgzi6vnA/N QdjFKlUxCB7HHuv35IoRCo/TfkN0Spei1dAGj0fuEncxy5soGR5a+brT+jsc82k94uFb4X u1ltUZq3fdxC4p4/VMqgSmsMRRGl6GZtx8oXm3A4Mh2ulVZCaBY7Yq5RJMFBm+EJLLlWn3 jGaI7CP1BjgvhaRUUXHfYxZsmiZXGRZPK0oJVId0C9Tdv/ZqchHJFw0c90fB4f2p+anNXt ty9maGcDltboPSIyzJPMlyfDtz33/QK1r/+aJNOjsELPW5Rsik8YU2ww0UIjxQ== From: Luca Ceresoli Date: Tue, 11 Nov 2025 13:01:23 +0100 Subject: [PATCH v4 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: <20251111-drm-bridge-alloc-encoder-chain-mutex-v4-3-12b13eb8c0f8@bootlin.com> References: <20251111-drm-bridge-alloc-encoder-chain-mutex-v4-0-12b13eb8c0f8@bootlin.com> In-Reply-To: <20251111-drm-bridge-alloc-encoder-chain-mutex-v4-0-12b13eb8c0f8@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 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 8f355df883d8ac8de9d361ec302f4ccbf3bca0d6..c8389383e0d286c0d576ae1864e= e783e002d44be 100644 --- a/drivers/gpu/drm/drm_bridge.c +++ b/drivers/gpu/drm/drm_bridge.c @@ -462,10 +462,12 @@ 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); @@ -496,7 +498,9 @@ 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 2.51.1