From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from ale.deltatee.com (ale.deltatee.com [204.191.154.188]) (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 98EC0392C56; Tue, 18 Aug 2026 16:22:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=204.191.154.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787070125; cv=none; b=fc4SMIUQDFc/oaWD1+gAFMOETp7PXpozwn6ZST2kTrziAfkzbdFDHBtZP3EniqUAY2+hb9qMqxwFji5PklwjgSyLTkWiSekAjQ/7FjZ6eysmtdVq15mfXGaVV1bIvbMXz5R3k39/f70hkmmGzSwwL+myB++iSy1mmFdd/wH96R4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787070125; c=relaxed/simple; bh=MHuo5CCg5FPgnXwZaXG7MDvuz4t39Kg+ZeD1Nl+DRT0=; h=Message-ID:Date:MIME-Version:To:Cc:References:From:In-Reply-To: Content-Type:Subject; b=aBLQN2xYEnbPBLW+hDFOh6KCFa7Ckz0pyR1m9XfmbGmmOdXb6iXh9aX2YAjUV6L9CZDA9HKsGjgp8nffPXxuLIQ8X2mAwaDCzc7WV0CL9i4iMjOb7jCS6ppaUsLXeup8zf6hE2+VIVcVXmOYIL4JcmSvlEk9M/P1bAHZIMvOmlc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=deltatee.com; spf=pass smtp.mailfrom=deltatee.com; dkim=pass (2048-bit key) header.d=deltatee.com header.i=@deltatee.com header.b=p8Hocy0m; arc=none smtp.client-ip=204.191.154.188 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=deltatee.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=deltatee.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=deltatee.com header.i=@deltatee.com header.b="p8Hocy0m" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=deltatee.com; s=20200525; h=Subject:In-Reply-To:From:References:Cc:To: MIME-Version:Date:Message-ID:content-disposition; bh=NCpNajcjLcKhB50ECJ7NOsUtAJuVK2tIlFJWyWHXWJQ=; b=p8Hocy0mI2ANMtc1ZYGcuSUp/N n7E/5SvgMicWEMlf57SNQAX8VSwNSgOv26/XYK6iSHdGuC9Z5+cY7VES/i354ObEJAyoyZqqXZLvc E9GaUvpquRWvFeQTCHWf0ks6tbc1GmsD1sc4nw2Bn7dLRMP/XmbcJsi/DpkFDtkixi5p7GCzMThg4 GTDr6a4tPjKA5WH1Pp9Vg52907Utmf2nc+OIfAA1alzE0CZnF2kP4SQRY0IXI9/VYkXlz0pQzuSVq 5jTNMjQ/lCO05mxedLpX2fZE9pqzX3ALJe9rlGCCX3z3/arnZUHagxG9IuZ0DkuzizdQUZ95rEXJg 50Un9nxg==; Received: from guinness.priv.deltatee.com ([172.16.1.162]) by ale.deltatee.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.98.2) (envelope-from ) id 1wwMZZ-00000000q31-1Eso; Tue, 18 Aug 2026 10:21:57 -0600 Message-ID: Date: Tue, 18 Aug 2026 10:21:56 -0600 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Shivank Garg , Vinod Koul , Frank Li , Andrew Morton Cc: stable@vger.kernel.org, dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, Sashiko , Frank Li References: <20260818-dmaengine-kref-fix-v4-0-c6ef991462a0@amd.com> <20260818-dmaengine-kref-fix-v4-4-c6ef991462a0@amd.com> Content-Language: en-CA From: Logan Gunthorpe In-Reply-To: <20260818-dmaengine-kref-fix-v4-4-c6ef991462a0@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 172.16.1.162 X-SA-Exim-Rcpt-To: shivankg@amd.com, vkoul@kernel.org, Frank.Li@kernel.org, akpm@linux-foundation.org, stable@vger.kernel.org, dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, sashiko-bot@kernel.org, Frank.Li@nxp.com X-SA-Exim-Mail-From: logang@deltatee.com X-Spam-Level: Subject: Re: [PATCH v4 4/4] dmaengine: wait for RCU readers before releasing dma_device X-SA-Exim-Version: 4.2.1 (built Sun, 23 Feb 2025 07:57:16 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) On 2026-08-17 21:43, Shivank Garg wrote: > diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c > index d075051dd187..604c9af19936 100644 > --- a/drivers/dma/dmaengine.c > +++ b/drivers/dma/dmaengine.c > @@ -429,6 +429,12 @@ static void dma_device_release(struct kref *ref) > list_del_rcu(&device->global_node); > dma_channel_rebalance(); > > + /* > + * Wait for RCU readers (e.g. dma_issue_pending_all()) that may still > + * be traversing dma_device_list before the device is freed. > + */ > + synchronize_rcu(); > + > if (device->device_release) > device->device_release(device); > } > A couple minor points on this: 1. I think the comment, as is, isn't useful. It's pretty clear the synchronize_rcu() call is paired with the list_del_rcu() call above it. 2. The new synchronize_rcu() call will delay for a grace period with the dma_list_mutex lock held. Is that okay? It might be, but if so, it could use a note in the commit message. Besides that, these are minor points and the patch does fix a real issue so: Reviewed-by: Logan Gunthorpe Thanks, Logan