From patchwork Thu Jul 28 01:40:57 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tetsuo Handa X-Patchwork-Id: 12930941 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 C100CC04A68 for ; Thu, 28 Jul 2022 01:41:40 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id A5175C835A; Thu, 28 Jul 2022 01:41:22 +0000 (UTC) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp [202.181.97.72]) by gabe.freedesktop.org (Postfix) with ESMTPS id DB8FDA7502 for ; Thu, 28 Jul 2022 01:41:02 +0000 (UTC) Received: from fsav117.sakura.ne.jp (fsav117.sakura.ne.jp [27.133.134.244]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 26S1exb2028265; Thu, 28 Jul 2022 10:40:59 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav117.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav117.sakura.ne.jp); Thu, 28 Jul 2022 10:40:59 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav117.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 26S1exQ6028262 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Thu, 28 Jul 2022 10:40:59 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Message-ID: <216591bc-28bb-0453-10bb-59e268dff540@I-love.SAKURA.ne.jp> Date: Thu, 28 Jul 2022 10:40:57 +0900 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Content-Language: en-US To: Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , David Airlie , Daniel Vetter From: Tetsuo Handa Subject: [PATCH v3] gpu/drm/bridge/cadence: avoid flush_scheduled_work() usage 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: , Cc: Andrew Morton , DRI Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Like commit c4f135d643823a86 ("workqueue: Wrap flush_workqueue() using a macro") says, flush_scheduled_work() is dangerous and will be forbidden. We are on the way for removing all flush_scheduled_work() callers from the kernel, and this patch is for removing flush_scheduled_work() call from cadence driver. Since cdns-mhdp8546 driver uses 4 works mhdp->modeset_retry_work mhdp->hpd_work mhdp->hdcp.check_work mhdp->hdcp.prop_work I assume that flush_scheduled_work() in cdns_mhdp_remove() needs to wait for only these 4 works. Since mhdp->modeset_retry_work already uses cancel_work_sync(), I assume that flush_scheduled_work() needs to wait for only 3 works. But I came to wonder whether mhdp->hdcp.check_work should be flushed or cancelled. While flush_scheduled_work() waits for completion of works which were already queued to system_wq, mhdp->hdcp.check_work is a delayed work. That is, this work won't be queued to system_wq unless timeout expires. Current code will wait for mhdp->hdcp.check_work only if timeout already expired. If timeout is not expired yet, flush_scheduled_work() will fail to cancel mhdp->hdcp.check_work, and cdns_mhdp_hdcp_check_work() which is triggered by mhdp->hdcp.check_work will schedule hdcp->check_work, which is too late for flush_scheduled_work() to wait for completion of cdns_mhdp_hdcp_prop_work(). But since I couldn't get comments on how do we want to handle this race window [1], this patch chose "do nothing" for mhdp->hdcp.check_work and mhdp->hdcp.prop_work. That is, I assume that flush_scheduled_work() in cdns_mhdp_remove() needs to wait for only mhdp->hpd_work work. Link: https://lkml.kernel.org/r/943273cb-c2ec-24e3-5edb-64eacc6e2d30@I-love.SAKURA.ne.jp [1] Signed-off-by: Tetsuo Handa --- drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c index ab63e7b11944..31442a922502 100644 --- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c +++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c @@ -2605,7 +2605,8 @@ static int cdns_mhdp_remove(struct platform_device *pdev) pm_runtime_disable(&pdev->dev); cancel_work_sync(&mhdp->modeset_retry_work); - flush_scheduled_work(); + flush_work(&mhdp->hpd_work); + /* Ignoring mhdp->hdcp.check_work and mhdp->hdcp.prop_work here. */ clk_disable_unprepare(mhdp->clk);