[PATCH v6 6/8] fsl-dma: use spin_lock_bh to instead of spin_lock_irqsave

Subsystems: dma generic offload engine subsystem, freescale dma driver, the rest

STALE5114d REVIEWED: 1 (0M)

1 review trailer.

3 messages, 3 authors, 2012-08-07 · open the first message on its own page

[PATCH v6 6/8] fsl-dma: use spin_lock_bh to instead of spin_lock_irqsave

From: <hidden>
Date: 2012-08-06 11:02:16

From: Qiang Liu <redacted>

The use of spin_lock_irqsave() is a stronger locking mechanism than is
required throughout the driver. The minimum locking required should be
used instead. Interrupts will be turned off and context will be saved,
there is needless to use irqsave.

Change all instances of spin_lock_irqsave() to spin_lock_bh().
All manipulation of protected fields is done using tasklet context or
weaker, which makes spin_lock_bh() the correct choice.

Cc: Dan Williams <redacted>
Cc: Dan Williams <redacted>
Cc: Vinod Koul <redacted>
Cc: Li Yang <redacted>
Cc: Timur Tabi <redacted>
Signed-off-by: Qiang Liu <redacted>
Acked-by: Ira W. Snyder <redacted>
---
 drivers/dma/fsldma.c |   30 ++++++++++++------------------
 1 files changed, 12 insertions(+), 18 deletions(-)

diff --git a/drivers/dma/fsldma.c b/drivers/dma/fsldma.c
index 938d8c1..3f809df 100644
--- a/drivers/dma/fsldma.c
+++ b/drivers/dma/fsldma.c

@@ -405,10 +405,9 @@ static dma_cookie_t fsl_dma_tx_submit(struct dma_async_tx_descriptor *tx)
 	struct fsldma_chan *chan = to_fsl_chan(tx->chan);
 	struct fsl_desc_sw *desc = tx_to_fsl_desc(tx);
 	struct fsl_desc_sw *child;
-	unsigned long flags;
 	dma_cookie_t cookie;

-	spin_lock_irqsave(&chan->desc_lock, flags);
+	spin_lock_bh(&chan->desc_lock);

 	/*
 	 * assign cookies to all of the software descriptors

@@ -421,7 +420,7 @@ static dma_cookie_t fsl_dma_tx_submit(struct dma_async_tx_descriptor *tx)
 	/* put this transaction onto the tail of the pending queue */
 	append_ld_queue(chan, desc);

-	spin_unlock_irqrestore(&chan->desc_lock, flags);
+	spin_unlock_bh(&chan->desc_lock);

 	return cookie;
 }

@@ -761,15 +760,14 @@ static void fsldma_free_desc_list_reverse(struct fsldma_chan *chan,
 static void fsl_dma_free_chan_resources(struct dma_chan *dchan)
 {
 	struct fsldma_chan *chan = to_fsl_chan(dchan);
-	unsigned long flags;

 	chan_dbg(chan, "free all channel resources\n");
-	spin_lock_irqsave(&chan->desc_lock, flags);
+	spin_lock_bh(&chan->desc_lock);
 	fsldma_cleanup_descriptors(chan);
 	fsldma_free_desc_list(chan, &chan->ld_pending);
 	fsldma_free_desc_list(chan, &chan->ld_running);
 	fsldma_free_desc_list(chan, &chan->ld_completed);
-	spin_unlock_irqrestore(&chan->desc_lock, flags);
+	spin_unlock_bh(&chan->desc_lock);

 	dma_pool_destroy(chan->desc_pool);
 	chan->desc_pool = NULL;

@@ -988,7 +986,6 @@ static int fsl_dma_device_control(struct dma_chan *dchan,
 {
 	struct dma_slave_config *config;
 	struct fsldma_chan *chan;
-	unsigned long flags;
 	int size;

 	if (!dchan)

@@ -998,7 +995,7 @@ static int fsl_dma_device_control(struct dma_chan *dchan,

 	switch (cmd) {
 	case DMA_TERMINATE_ALL:
-		spin_lock_irqsave(&chan->desc_lock, flags);
+		spin_lock_bh(&chan->desc_lock);

 		/* Halt the DMA engine */
 		dma_halt(chan);

@@ -1009,7 +1006,7 @@ static int fsl_dma_device_control(struct dma_chan *dchan,
 		fsldma_free_desc_list(chan, &chan->ld_completed);
 		chan->idle = true;

-		spin_unlock_irqrestore(&chan->desc_lock, flags);
+		spin_unlock_bh(&chan->desc_lock);
 		return 0;

 	case DMA_SLAVE_CONFIG:

@@ -1051,11 +1048,10 @@ static int fsl_dma_device_control(struct dma_chan *dchan,
 static void fsl_dma_memcpy_issue_pending(struct dma_chan *dchan)
 {
 	struct fsldma_chan *chan = to_fsl_chan(dchan);
-	unsigned long flags;

-	spin_lock_irqsave(&chan->desc_lock, flags);
+	spin_lock_bh(&chan->desc_lock);
 	fsl_chan_xfer_ld_queue(chan);
-	spin_unlock_irqrestore(&chan->desc_lock, flags);
+	spin_unlock_bh(&chan->desc_lock);
 }

 /**

@@ -1068,15 +1064,14 @@ static enum dma_status fsl_tx_status(struct dma_chan *dchan,
 {
 	struct fsldma_chan *chan = to_fsl_chan(dchan);
 	enum dma_status ret;
-	unsigned long flags;

 	ret = dma_cookie_status(dchan, cookie, txstate);
 	if (ret == DMA_SUCCESS)
 		return ret;

-	spin_lock_irqsave(&chan->desc_lock, flags);
+	spin_lock_bh(&chan->desc_lock);
 	fsldma_cleanup_descriptors(chan);
-	spin_unlock_irqrestore(&chan->desc_lock, flags);
+	spin_unlock_bh(&chan->desc_lock);

 	return dma_cookie_status(dchan, cookie, txstate);
 }

@@ -1155,11 +1150,10 @@ static irqreturn_t fsldma_chan_irq(int irq, void *data)
 static void dma_do_tasklet(unsigned long data)
 {
 	struct fsldma_chan *chan = (struct fsldma_chan *)data;
-	unsigned long flags;

 	chan_dbg(chan, "tasklet entry\n");

-	spin_lock_irqsave(&chan->desc_lock, flags);
+	spin_lock_bh(&chan->desc_lock);

 	/* the hardware is now idle and ready for more */
 	chan->idle = true;

@@ -1167,7 +1161,7 @@ static void dma_do_tasklet(unsigned long data)
 	/* Run all cleanup for descriptors which have been completed */
 	fsldma_cleanup_descriptors(chan);

-	spin_unlock_irqrestore(&chan->desc_lock, flags);
+	spin_unlock_bh(&chan->desc_lock);

 	chan_dbg(chan, "tasklet exit\n");
 }
--

1.7.5.1

Re: [PATCH v6 6/8] fsl-dma: use spin_lock_bh to instead of spin_lock_irqsave

From: Arnd Bergmann <arnd@arndb.de>
Date: 2012-08-06 11:57:44

On Monday 06 August 2012, qiang.liu@freescale.com wrote:

From: Qiang Liu <redacted>

The use of spin_lock_irqsave() is a stronger locking mechanism than is
required throughout the driver. The minimum locking required should be
used instead. Interrupts will be turned off and context will be saved,
there is needless to use irqsave.

Change all instances of spin_lock_irqsave() to spin_lock_bh().
All manipulation of protected fields is done using tasklet context or
weaker, which makes spin_lock_bh() the correct choice.

Cc: Dan Williams <redacted>
Cc: Dan Williams <redacted>
Cc: Vinod Koul <redacted>
Cc: Li Yang <redacted>
Cc: Timur Tabi <redacted>
Signed-off-by: Qiang Liu <redacted>
Acked-by: Ira W. Snyder <redacted>

Acked-by: Arnd Bergmann <arnd@arndb.de>

You could actually change the use of spin_lock_bh inside of the tasklet
function (dma_do_tasklet) do just spin_lock(), because softirqs are
already disabled there, but your version is also ok.

RE: [PATCH v6 6/8] fsl-dma: use spin_lock_bh to instead of spin_lock_irqsave

From: Liu Qiang-B32616 <hidden>
Date: 2012-08-07 02:46:12

-----Original Message-----
From: Arnd Bergmann [mailto:arnd@arndb.de]
Sent: Monday, August 06, 2012 7:57 PM
To: Liu Qiang-B32616
Cc: linux-crypto@vger.kernel.org; linuxppc-dev@lists.ozlabs.org;
dan.j.williams@intel.com; linux-kernel@vger.kernel.org;
dan.j.williams@gmail.com; vinod.koul@intel.com; Phillips Kim-R1AAHA;
herbert@gondor.hengli.com.au; davem@davemloft.net;
gregkh@linuxfoundation.org; Li Yang-R58472; Tabi Timur-B04825
Subject: Re: [PATCH v6 6/8] fsl-dma: use spin_lock_bh to instead of
spin_lock_irqsave
=20
On Monday 06 August 2012, qiang.liu@freescale.com wrote:

quoted

From: Qiang Liu <redacted>

The use of spin_lock_irqsave() is a stronger locking mechanism than is
required throughout the driver. The minimum locking required should be
used instead. Interrupts will be turned off and context will be saved,
there is needless to use irqsave.

Change all instances of spin_lock_irqsave() to spin_lock_bh().
All manipulation of protected fields is done using tasklet context or
weaker, which makes spin_lock_bh() the correct choice.

Cc: Dan Williams <redacted>
Cc: Dan Williams <redacted>
Cc: Vinod Koul <redacted>
Cc: Li Yang <redacted>
Cc: Timur Tabi <redacted>
Signed-off-by: Qiang Liu <redacted>
Acked-by: Ira W. Snyder <redacted>

=20
Acked-by: Arnd Bergmann <arnd@arndb.de>
=20
You could actually change the use of spin_lock_bh inside of the tasklet
function (dma_do_tasklet) do just spin_lock(), because softirqs are
already disabled there, but your version is also ok.

Yes, you are right, it will disable softirq.
Thank you very much.

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