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Thu, 23 Jan 2020 14:03:11 +0000 From: To: , , CC: , , Subject: [PATCH 06/10] dmaengine: at_hdmac: Fix deadlocks Thread-Topic: [PATCH 06/10] dmaengine: at_hdmac: Fix deadlocks Thread-Index: AQHV0fXYj/5vVpZ6cU+eOuaVKc1MfA== Date: Thu, 23 Jan 2020 14:03:11 +0000 Message-ID: <20200123140237.125799-6-tudor.ambarus@microchip.com> References: <20200123140237.125799-1-tudor.ambarus@microchip.com> In-Reply-To: <20200123140237.125799-1-tudor.ambarus@microchip.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [94.177.32.156] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 221aabc6-2667-4a95-87db-08d7a00cfb60 x-ms-traffictypediagnostic: MN2PR11MB4190: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:4502; x-forefront-prvs: 029174C036 x-forefront-antispam-report: SFV:NSPM;SFS:(10009020)(39860400002)(376002)(136003)(346002)(396003)(366004)(199004)(189003)(1076003)(76116006)(91956017)(66446008)(64756008)(66476007)(66946007)(66556008)(6506007)(86362001)(107886003)(2906002)(71200400001)(8936002)(4326008)(26005)(54906003)(36756003)(316002)(2616005)(6486002)(110136005)(81156014)(5660300002)(8676002)(6512007)(186003)(478600001)(81166006);DIR:OUT;SFP:1101;SCL:1;SRVR:MN2PR11MB4190;H:MN2PR11MB4448.namprd11.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;A:1;MX:1; received-spf: None (protection.outlook.com: microchip.com does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: DZypPEbolAIOzBQA35VpOpOwTqosrHbMmMzxWQ83gAJ2QdN+ZJ17LvQrBco894NM7AQf6WAysBTPYi5ojy/YSkBVFqHc861fZgX9LWVtoGTWh143JWMA5LUM0odHa6qjSdzVKSWL0HP9f9fnCtvr+jTLf5isw8DLlYzOBVqkHjlrFlmXt811kQ5Sf7SfhNkbdfL7d2MgSYWqU7FoSjPyZIt9HZ9QrYk8ONEsL2fln44qhNIUdQOlFWGCTvSeQigfmkwrv4kXmSky9HB6LFtHM4z4ghc76574179rgb/rEuYrRuDyT+7BAJbuHlkOnAempZMrmDmeIWmpmcyPiPL2t0sD+x14Tr7b2x8/JIYQ1HcjuNKORYLH9SbdGGLNOm7RKv0TjWUBKYP866ozfmrZ+HHLm7659mwnkV+FbOjmBUd9brzefgDtEj2AHcm4GVz8 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 221aabc6-2667-4a95-87db-08d7a00cfb60 X-MS-Exchange-CrossTenant-originalarrivaltime: 23 Jan 2020 14:03:11.1964 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 3f4057f3-b418-4d4e-ba84-d55b4e897d88 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: V+oelASSJP+O22YGr1inOgQWIq8TlKZmPEwIkrFGR2dnQ1IEgrbxLW7RlEtQLYCwCHNU4IdfHiyR+32JPkdthK1eU43Nt3lZDt3luZeBK+U= X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR11MB4190 Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org From: Tudor Ambarus Fix the following deadlocks: 1/ atc_handle_cyclic() and atc_chain_complete() called dmaengine_desc_get_callback_invoke() while wrongly holding the atchan->lock. Clients can set the callback to dmaengine_terminate_sync() which will end up trying to get the same lock, thus a deadlock occurred. 2/ dma_run_dependencies() was called with the atchan->lock held, but the method calls device_issue_pending() which tries to get the same lock, and so a deadlock occurred. The driver must not hold the lock when invoking the callback or when running dependencies. Releasing the spinlock within a called function before calling the callback is not a nice thing to do -> called functions become non-atomic when called within an atomic region. Thus the lock is now taken in the child routines whereever is needed. Signed-off-by: Tudor Ambarus --- drivers/dma/at_hdmac.c | 74 ++++++++++++++++++++++-------------------- 1 file changed, 39 insertions(+), 35 deletions(-) diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c index 8e8e04bd1b28..73a20780744b 100644 --- a/drivers/dma/at_hdmac.c +++ b/drivers/dma/at_hdmac.c @@ -426,17 +426,19 @@ static int atc_get_bytes_left(struct dma_chan *chan, = dma_cookie_t cookie) * atc_chain_complete - finish work for one transaction chain * @atchan: channel we work on * @desc: descriptor at the head of the chain we want do complete - * - * Called with atchan->lock held and bh disabled */ + */ static void atc_chain_complete(struct at_dma_chan *atchan, struct at_desc *desc) { struct dma_async_tx_descriptor *txd =3D &desc->txd; struct at_dma *atdma =3D to_at_dma(atchan->chan_common.device); + unsigned long flags; =20 dev_vdbg(chan2dev(&atchan->chan_common), "descriptor %u complete\n", txd->cookie); =20 + spin_lock_irqsave(&atchan->lock, flags); + /* mark the descriptor as complete for non cyclic cases only */ if (!atc_chan_is_cyclic(atchan)) dma_cookie_complete(txd); @@ -453,16 +455,13 @@ atc_chain_complete(struct at_dma_chan *atchan, struct= at_desc *desc) /* move myself to free_list */ list_move(&desc->desc_node, &atchan->free_list); =20 + spin_unlock_irqrestore(&atchan->lock, flags); + dma_descriptor_unmap(txd); /* for cyclic transfers, * no need to replay callback function while stopping */ - if (!atc_chan_is_cyclic(atchan)) { - /* - * The API requires that no submissions are done from a - * callback, so we don't need to drop the lock here - */ + if (!atc_chan_is_cyclic(atchan)) dmaengine_desc_get_callback_invoke(txd, NULL); - } =20 dma_run_dependencies(txd); } @@ -480,9 +479,12 @@ static void atc_complete_all(struct at_dma_chan *atcha= n) { struct at_desc *desc, *_desc; LIST_HEAD(list); + unsigned long flags; =20 dev_vdbg(chan2dev(&atchan->chan_common), "complete all\n"); =20 + spin_lock_irqsave(&atchan->lock, flags); + /* * Submit queued descriptors ASAP, i.e. before we go through * the completed ones. @@ -494,6 +496,8 @@ static void atc_complete_all(struct at_dma_chan *atchan= ) /* empty queue list by moving descriptors (if any) to active_list */ list_splice_init(&atchan->queue, &atchan->active_list); =20 + spin_unlock_irqrestore(&atchan->lock, flags); + list_for_each_entry_safe(desc, _desc, &list, desc_node) atc_chain_complete(atchan, desc); } @@ -501,38 +505,44 @@ static void atc_complete_all(struct at_dma_chan *atch= an) /** * atc_advance_work - at the end of a transaction, move forward * @atchan: channel where the transaction ended - * - * Called with atchan->lock held and bh disabled */ static void atc_advance_work(struct at_dma_chan *atchan) { + unsigned long flags; + int ret; + dev_vdbg(chan2dev(&atchan->chan_common), "advance_work\n"); =20 - if (atc_chan_is_enabled(atchan)) + spin_lock_irqsave(&atchan->lock, flags); + ret =3D atc_chan_is_enabled(atchan); + spin_unlock_irqrestore(&atchan->lock, flags); + if (ret) return; =20 if (list_empty(&atchan->active_list) || - list_is_singular(&atchan->active_list)) { - atc_complete_all(atchan); - } else { - atc_chain_complete(atchan, atc_first_active(atchan)); - /* advance work */ - atc_dostart(atchan, atc_first_active(atchan)); - } + list_is_singular(&atchan->active_list)) + return atc_complete_all(atchan); + + atc_chain_complete(atchan, atc_first_active(atchan)); + + /* advance work */ + spin_lock_irqsave(&atchan->lock, flags); + atc_dostart(atchan, atc_first_active(atchan)); + spin_unlock_irqrestore(&atchan->lock, flags); } =20 =20 /** * atc_handle_error - handle errors reported by DMA controller * @atchan: channel where error occurs - * - * Called with atchan->lock held and bh disabled */ static void atc_handle_error(struct at_dma_chan *atchan) { struct at_desc *bad_desc; struct at_desc *child; + unsigned long flags; =20 + spin_lock_irqsave(&atchan->lock, flags); /* * The descriptor currently at the head of the active list is * broked. Since we don't have any way to report errors, we'll @@ -564,6 +574,8 @@ static void atc_handle_error(struct at_dma_chan *atchan= ) list_for_each_entry(child, &bad_desc->tx_list, desc_node) atc_dump_lli(atchan, &child->lli); =20 + spin_unlock_irqrestore(&atchan->lock, flags); + /* Pretend the descriptor completed successfully */ atc_chain_complete(atchan, bad_desc); } @@ -571,8 +583,6 @@ static void atc_handle_error(struct at_dma_chan *atchan= ) /** * atc_handle_cyclic - at the end of a period, run callback function * @atchan: channel used for cyclic operations - * - * Called with atchan->lock held and bh disabled */ static void atc_handle_cyclic(struct at_dma_chan *atchan) { @@ -591,17 +601,14 @@ static void atc_handle_cyclic(struct at_dma_chan *atc= han) static void atc_tasklet(unsigned long data) { struct at_dma_chan *atchan =3D (struct at_dma_chan *)data; - unsigned long flags; =20 - spin_lock_irqsave(&atchan->lock, flags); if (test_and_clear_bit(ATC_IS_ERROR, &atchan->status)) - atc_handle_error(atchan); - else if (atc_chan_is_cyclic(atchan)) - atc_handle_cyclic(atchan); - else - atc_advance_work(atchan); + return atc_handle_error(atchan); =20 - spin_unlock_irqrestore(&atchan->lock, flags); + if (atc_chan_is_cyclic(atchan)) + return atc_handle_cyclic(atchan); + + atc_advance_work(atchan); } =20 static irqreturn_t at_dma_interrupt(int irq, void *dev_id) @@ -1437,6 +1444,8 @@ static int atc_terminate_all(struct dma_chan *chan) list_splice_init(&atchan->queue, &list); list_splice_init(&atchan->active_list, &list); =20 + spin_unlock_irqrestore(&atchan->lock, flags); + /* Flush all pending and queued descriptors */ list_for_each_entry_safe(desc, _desc, &list, desc_node) atc_chain_complete(atchan, desc); @@ -1445,8 +1454,6 @@ static int atc_terminate_all(struct dma_chan *chan) /* if channel dedicated to cyclic operations, free it */ clear_bit(ATC_IS_CYCLIC, &atchan->status); =20 - spin_unlock_irqrestore(&atchan->lock, flags); - return 0; } =20 @@ -1507,7 +1514,6 @@ atc_tx_status(struct dma_chan *chan, static void atc_issue_pending(struct dma_chan *chan) { struct at_dma_chan *atchan =3D to_at_dma_chan(chan); - unsigned long flags; =20 dev_vdbg(chan2dev(chan), "issue_pending\n"); =20 @@ -1515,9 +1521,7 @@ static void atc_issue_pending(struct dma_chan *chan) if (atc_chan_is_cyclic(atchan)) return; =20 - spin_lock_irqsave(&atchan->lock, flags); atc_advance_work(atchan); - spin_unlock_irqrestore(&atchan->lock, flags); } =20 /** --=20 2.23.0