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Thu, 9 Apr 2026 11:56:40 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1775728602; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:content-language:in-reply-to:references; bh=og7A9CWzp20T8+kYE/xTpokPQuPu0SDZDu89tndMdLA=; b=UMAlW2Y62sGPi/u4DoDpeipzrWHCGCC11F2qNPZiamRZTrfBYs0F3Pa1rNwoQKuo2sreZ6 2DiSzF/Sm2x6wd5J3b0Z1p8rbHXvj03goSL0D5rdA1VPJMzOH6Y79bVgV/w58GY3WXHAgy BmFBgA0ILX+9zrdatetxWuzP5HJOdrS5/EVHYaeLzjNkF14BQSRzNok0yEkfVxnU/Mn/28 Xh5fW5NycNyl62Ud3M9agLAbQmgxyNdhJLKPvN2LzUTiJq3uCq5unyq5V31di39uTkQP9V INKptbEoJ8rzoQYTE4iPxEhD8qcWsktqd4f+yXJ7RdAkG0pyZB+nrMi2QzPObw== Message-ID: Date: Thu, 9 Apr 2026 11:56:39 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 3/7] drm/bridge: drm_bridge_attach: lock the encoder chain mutex during insertion To: Luca Ceresoli , 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 References: <20260324-drm-bridge-alloc-encoder-chain-mutex-v5-0-8bf786c5c7e6@bootlin.com> <20260324-drm-bridge-alloc-encoder-chain-mutex-v5-3-8bf786c5c7e6@bootlin.com> Content-Language: en-US From: Louis Chauvet In-Reply-To: <20260324-drm-bridge-alloc-encoder-chain-mutex-v5-3-8bf786c5c7e6@bootlin.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Last-TLS-Session-Version: TLSv1.3 On 3/24/26 9:58 AM, Luca Ceresoli wrote: > 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 Reviewed-by: Louis Chauvet > --- > > 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, struct drm_bridge *bridge, > bridge->dev = encoder->dev; > bridge->encoder = encoder; > > + 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); > > if (bridge->funcs->attach) { > ret = bridge->funcs->attach(bridge, encoder, flags); > @@ -594,7 +596,9 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge, > err_reset_bridge: > bridge->dev = NULL; > bridge->encoder = NULL; > + mutex_lock(&encoder->bridge_chain_mutex); > list_del(&bridge->chain_node); > + mutex_unlock(&encoder->bridge_chain_mutex); > > if (ret != -EPROBE_DEFER) > DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n", >