From patchwork Thu Sep 21 20:53:55 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mikulas Patocka X-Patchwork-Id: 13394666 X-Patchwork-Delegate: herbert@gondor.apana.org.au 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A263FE7D0AB for ; Thu, 21 Sep 2023 21:24:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232607AbjIUVYV (ORCPT ); Thu, 21 Sep 2023 17:24:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56260 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230290AbjIUVYH (ORCPT ); Thu, 21 Sep 2023 17:24:07 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 80A2CE098 for ; Thu, 21 Sep 2023 13:54:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1695329639; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type; bh=fGPKZrXt//Yq5gMCYOETARqtGaAshsB1GXsDehnSEAY=; b=EHHWXfeeO2+0YUNZNT78QSTuauDeVA+OukoL2i+9doDEkdc0U292SkzGbB8iwkDdtTRTSS 3xDNzWLs8ikCFjS5kSF4RuLskxeuhSpH1ebAn4V67xUbptPg7Kw2cwAq6cSb9ISBX/AyYd BDCtRKXG6IJ2hMmM+4zDMqPtRqhd88A= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-508-vIAPiOWSOGmX5UhEXrpHjw-1; Thu, 21 Sep 2023 16:53:56 -0400 X-MC-Unique: vIAPiOWSOGmX5UhEXrpHjw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0A54D3814591; Thu, 21 Sep 2023 20:53:56 +0000 (UTC) Received: from file1-rdu.file-001.prod.rdu2.dc.redhat.com (unknown [10.11.5.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 610872156701; Thu, 21 Sep 2023 20:53:55 +0000 (UTC) Received: by file1-rdu.file-001.prod.rdu2.dc.redhat.com (Postfix, from userid 12668) id 4926030C1C0A; Thu, 21 Sep 2023 20:53:55 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by file1-rdu.file-001.prod.rdu2.dc.redhat.com (Postfix) with ESMTP id 406CF3FB77; Thu, 21 Sep 2023 22:53:55 +0200 (CEST) Date: Thu, 21 Sep 2023 22:53:55 +0200 (CEST) From: Mikulas Patocka To: Giovanni Cabiddu , Herbert Xu , "David S. Miller" , Michael Hrivnak , Eric Garver cc: qat-linux@intel.com, linux-crypto@vger.kernel.org, dm-devel@redhat.com Subject: [PATCH] qat: fix deadlock in backlog processing Message-ID: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org Hi I was evaluating whether it is feasible to use QAT with dm-crypt (the answer is that it is not - QAT is slower than AES-NI for this type of workload; QAT starts to be benefical for encryption requests longer than 64k). And I got some deadlocks. The reason for the deadlocks is this: suppose that one of the "if" conditions in "qat_alg_send_message_maybacklog" is true and we jump to the "enqueue" label. At this point, an interrupt comes in and clears all pending messages. Now, the interrupt returns, we grab backlog->lock, add the message to the backlog, drop backlog->lock - and there is no one to remove the backlogged message out of the list and submit it. I fixed it with this patch - with this patch, the test passes and there are no longer any deadlocks. I didn't want to add a spinlock to the hot path, so I take it only if some of the condition suggests that queuing may be required. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org --- drivers/crypto/intel/qat/qat_common/qat_algs_send.c | 31 ++++++++++++-------- 1 file changed, 20 insertions(+), 11 deletions(-) Index: linux-2.6/drivers/crypto/intel/qat/qat_common/qat_algs_send.c =================================================================== --- linux-2.6.orig/drivers/crypto/intel/qat/qat_common/qat_algs_send.c +++ linux-2.6/drivers/crypto/intel/qat/qat_common/qat_algs_send.c @@ -40,16 +40,6 @@ void qat_alg_send_backlog(struct qat_ins spin_unlock_bh(&backlog->lock); } -static void qat_alg_backlog_req(struct qat_alg_req *req, - struct qat_instance_backlog *backlog) -{ - INIT_LIST_HEAD(&req->list); - - spin_lock_bh(&backlog->lock); - list_add_tail(&req->list, &backlog->list); - spin_unlock_bh(&backlog->lock); -} - static int qat_alg_send_message_maybacklog(struct qat_alg_req *req) { struct qat_instance_backlog *backlog = req->backlog; @@ -71,8 +61,27 @@ static int qat_alg_send_message_maybackl return -EINPROGRESS; enqueue: - qat_alg_backlog_req(req, backlog); + spin_lock_bh(&backlog->lock); + + /* If any request is already backlogged, then add to backlog list */ + if (!list_empty(&backlog->list)) + goto enqueue2; + /* If ring is nearly full, then add to backlog list */ + if (adf_ring_nearly_full(tx_ring)) + goto enqueue2; + + /* If adding request to HW ring fails, then add to backlog list */ + if (adf_send_message(tx_ring, fw_req)) + goto enqueue2; + + spin_unlock_bh(&backlog->lock); + return -EINPROGRESS; + +enqueue2: + list_add_tail(&req->list, &backlog->list); + + spin_unlock_bh(&backlog->lock); return -EBUSY; }