From mboxrd@z Thu Jan 1 00:00:00 1970 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 913B3C43334 for ; Tue, 14 Jun 2022 08:41:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355697AbiFNIlT (ORCPT ); Tue, 14 Jun 2022 04:41:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36114 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353729AbiFNIlA (ORCPT ); Tue, 14 Jun 2022 04:41:00 -0400 Received: from mta-01.yadro.com (mta-02.yadro.com [89.207.88.252]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C16632A0 for ; Tue, 14 Jun 2022 01:40:32 -0700 (PDT) Received: from localhost (unknown [127.0.0.1]) by mta-01.yadro.com (Postfix) with ESMTP id 94FA842486 for ; Tue, 14 Jun 2022 08:40:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=yadro.com; h= content-type:content-type:content-transfer-encoding:mime-version :x-mailer:message-id:date:date:subject:subject:from:from :received:received:received:received; s=mta-01; t=1655196029; x= 1657010430; bh=pOWO5hgc75axpRyBMjnOfOPevFW7nwL569aKMrIMaf8=; b=i C517OhY76ihqgm9sgYzeSCWAxXu5pTCCLOxOPj/1VMNXMJR1zv8UvaR0s4wGVaU6 waMEY0NyAumDw8EpHGipqqvi+a2t8j1BMDrgoPDdBxzmJtzl3SbI+nipeV/b00ic E/6J9hRWtxffA5C1YHyHxSCRaWrofcTh5+PD2M+2E8= X-Virus-Scanned: amavisd-new at yadro.com Received: from mta-01.yadro.com ([127.0.0.1]) by localhost (mta-01.yadro.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Vz1eP23V5-y5 for ; Tue, 14 Jun 2022 11:40:29 +0300 (MSK) Received: from T-EXCH-02.corp.yadro.com (t-exch-02.corp.yadro.com [172.17.10.102]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mta-01.yadro.com (Postfix) with ESMTPS id 403CF421C2 for ; Tue, 14 Jun 2022 11:40:29 +0300 (MSK) Received: from T-Exch-05.corp.yadro.com (172.17.10.109) by T-EXCH-02.corp.yadro.com (172.17.10.102) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P384) id 15.1.669.32; Tue, 14 Jun 2022 11:40:29 +0300 Received: from v.yadro.com (10.178.114.10) by T-Exch-05.corp.yadro.com (172.17.10.109) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.2.792.3; Tue, 14 Jun 2022 11:40:28 +0300 From: Viacheslav Mitrofanov To: CC: , Viacheslav Mitrofanov Subject: [PATCH RESEND] dmaengine: sf-pdma: Add multithread support for a DMA channel Date: Tue, 14 Jun 2022 11:40:09 +0300 Message-ID: <20220614084009.70694-1-v.v.mitrofanov@yadro.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.178.114.10] X-ClientProxiedBy: T-EXCH-01.corp.yadro.com (172.17.10.101) To T-Exch-05.corp.yadro.com (172.17.10.109) Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org When we get a DMA channel and try to use it in multiple threads it will cause oops and hanging the system. % echo 64 > /sys/module/dmatest/parameters/threads_per_chan % echo 10000 > /sys/module/dmatest/parameters/iterations % echo 1 > /sys/module/dmatest/parameters/run [ 89.480664] Unable to handle kernel NULL pointer dereference at virtual address 00000000000000a0 [ 89.488725] Oops [#1] [ 89.494708] CPU: 2 PID: 1008 Comm: dma0chan0-copy0 Not tainted 5.17.0-rc5 [ 89.509385] epc : vchan_find_desc+0x32/0x46 [ 89.513553] ra : sf_pdma_tx_status+0xca/0xd6 This happens because of data race. Each thread rewrite channels's descriptor as soon as device_prep_dma_memcpy() is called. It leads to the situation when the driver thinks that it uses right descriptor that actually is freed or substituted for other one. With current fixes a descriptor changes its value only when it has been used. A new descriptor is acquired from vc->desc_issued queue that is already filled with descriptors that are ready to be sent. Threads have no direct access to DMA channel descriptor. Now it is just possible to queue a descriptor for further processing. Fixes: 6973886ad58e ("dmaengine: sf-pdma: add platform DMA support for HiFive Unleashed A00") Signed-off-by: Viacheslav Mitrofanov --- drivers/dma/sf-pdma/sf-pdma.c | 44 ++++++++++++++++++++++++----------- 1 file changed, 30 insertions(+), 14 deletions(-) diff --git a/drivers/dma/sf-pdma/sf-pdma.c b/drivers/dma/sf-pdma/sf-pdma.c index f12606aeff87..70bb032c59c2 100644 --- a/drivers/dma/sf-pdma/sf-pdma.c +++ b/drivers/dma/sf-pdma/sf-pdma.c @@ -52,16 +52,6 @@ static inline struct sf_pdma_desc *to_sf_pdma_desc(struct virt_dma_desc *vd) static struct sf_pdma_desc *sf_pdma_alloc_desc(struct sf_pdma_chan *chan) { struct sf_pdma_desc *desc; - unsigned long flags; - - spin_lock_irqsave(&chan->lock, flags); - - if (chan->desc && !chan->desc->in_use) { - spin_unlock_irqrestore(&chan->lock, flags); - return chan->desc; - } - - spin_unlock_irqrestore(&chan->lock, flags); desc = kzalloc(sizeof(*desc), GFP_NOWAIT); if (!desc) @@ -111,7 +101,6 @@ sf_pdma_prep_dma_memcpy(struct dma_chan *dchan, dma_addr_t dest, dma_addr_t src, desc->async_tx = vchan_tx_prep(&chan->vchan, &desc->vdesc, flags); spin_lock_irqsave(&chan->vchan.lock, iflags); - chan->desc = desc; sf_pdma_fill_desc(desc, dest, src, len); spin_unlock_irqrestore(&chan->vchan.lock, iflags); @@ -170,11 +159,17 @@ static size_t sf_pdma_desc_residue(struct sf_pdma_chan *chan, unsigned long flags; u64 residue = 0; struct sf_pdma_desc *desc; - struct dma_async_tx_descriptor *tx; + struct dma_async_tx_descriptor *tx = NULL; spin_lock_irqsave(&chan->vchan.lock, flags); - tx = &chan->desc->vdesc.tx; + list_for_each_entry(vd, &chan->vchan.desc_submitted, node) + if (vd->tx.cookie == cookie) + tx = &vd->tx; + + if (!tx) + goto out; + if (cookie == tx->chan->completed_cookie) goto out; @@ -241,6 +236,19 @@ static void sf_pdma_enable_request(struct sf_pdma_chan *chan) writel(v, regs->ctrl); } +static struct sf_pdma_desc *sf_pdma_get_first_pending_desc(struct sf_pdma_chan *chan) +{ + struct virt_dma_chan *vchan = &chan->vchan; + struct virt_dma_desc *vdesc; + + if (list_empty(&vchan->desc_issued)) + return NULL; + + vdesc = list_first_entry(&vchan->desc_issued, struct virt_dma_desc, node); + + return container_of(vdesc, struct sf_pdma_desc, vdesc); +} + static void sf_pdma_xfer_desc(struct sf_pdma_chan *chan) { struct sf_pdma_desc *desc = chan->desc; @@ -268,8 +276,11 @@ static void sf_pdma_issue_pending(struct dma_chan *dchan) spin_lock_irqsave(&chan->vchan.lock, flags); - if (vchan_issue_pending(&chan->vchan) && chan->desc) + if ((chan->desc == NULL) && vchan_issue_pending(&chan->vchan)) { + /* vchan_issue_pending has made a check that desc in not NULL */ + chan->desc = sf_pdma_get_first_pending_desc(chan); sf_pdma_xfer_desc(chan); + } spin_unlock_irqrestore(&chan->vchan.lock, flags); } @@ -298,6 +309,11 @@ static void sf_pdma_donebh_tasklet(struct tasklet_struct *t) spin_lock_irqsave(&chan->vchan.lock, flags); list_del(&chan->desc->vdesc.node); vchan_cookie_complete(&chan->desc->vdesc); + + chan->desc = sf_pdma_get_first_pending_desc(chan); + if (chan->desc) + sf_pdma_xfer_desc(chan); + spin_unlock_irqrestore(&chan->vchan.lock, flags); } -- 2.25.1