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Message-ID: <20200123140237.125799-6-tudor.ambarus@microchip.com>
Date: Thu, 23 Jan 2020 14:03:11 +0000
From: <Tudor.Ambarus@...rochip.com>
To: <Ludovic.Desroches@...rochip.com>, <dan.j.williams@...el.com>,
<vkoul@...nel.org>
CC: <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<Tudor.Ambarus@...rochip.com>
Subject: [PATCH 06/10] dmaengine: at_hdmac: Fix deadlocks
From: Tudor Ambarus <tudor.ambarus@...rochip.com>
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 <tudor.ambarus@...rochip.com>
---
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 = &desc->txd;
struct at_dma *atdma = to_at_dma(atchan->chan_common.device);
+ unsigned long flags;
dev_vdbg(chan2dev(&atchan->chan_common),
"descriptor %u complete\n", txd->cookie);
+ 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);
+ 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);
- }
dma_run_dependencies(txd);
}
@@ -480,9 +479,12 @@ static void atc_complete_all(struct at_dma_chan *atchan)
{
struct at_desc *desc, *_desc;
LIST_HEAD(list);
+ unsigned long flags;
dev_vdbg(chan2dev(&atchan->chan_common), "complete all\n");
+ 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);
+ 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 *atchan)
/**
* 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");
- if (atc_chan_is_enabled(atchan))
+ spin_lock_irqsave(&atchan->lock, flags);
+ ret = atc_chan_is_enabled(atchan);
+ spin_unlock_irqrestore(&atchan->lock, flags);
+ if (ret)
return;
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);
}
/**
* 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;
+ 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);
+ 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 *atchan)
static void atc_tasklet(unsigned long data)
{
struct at_dma_chan *atchan = (struct at_dma_chan *)data;
- unsigned long flags;
- 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);
- spin_unlock_irqrestore(&atchan->lock, flags);
+ if (atc_chan_is_cyclic(atchan))
+ return atc_handle_cyclic(atchan);
+
+ atc_advance_work(atchan);
}
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);
+ 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);
- spin_unlock_irqrestore(&atchan->lock, flags);
-
return 0;
}
@@ -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 = to_at_dma_chan(chan);
- unsigned long flags;
dev_vdbg(chan2dev(chan), "issue_pending\n");
@@ -1515,9 +1521,7 @@ static void atc_issue_pending(struct dma_chan *chan)
if (atc_chan_is_cyclic(atchan))
return;
- spin_lock_irqsave(&atchan->lock, flags);
atc_advance_work(atchan);
- spin_unlock_irqrestore(&atchan->lock, flags);
}
/**
--
2.23.0
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