Re: [PATCH] staging: comedi: usbduxfast: Improve unlocking of a mutex in usbduxfast_ai_insn_read()

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On 02/11/17 19:40, SF Markus Elfring wrote:
From: Markus Elfring <elfring@xxxxxxxxxxxxxxxxxxxxx>
Date: Thu, 2 Nov 2017 20:30:31 +0100

* Add a jump target so that a call of the function "mutex_unlock" is stored
   only twice in this function implementation.

* Replace five calls by goto statements.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@xxxxxxxxxxxxxxxxxxxxx>
---
  drivers/staging/comedi/drivers/usbduxfast.c | 24 ++++++++++++------------
  1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/drivers/staging/comedi/drivers/usbduxfast.c b/drivers/staging/comedi/drivers/usbduxfast.c
index 608403c7586b..e5884faf7275 100644
--- a/drivers/staging/comedi/drivers/usbduxfast.c
+++ b/drivers/staging/comedi/drivers/usbduxfast.c
@@ -777,8 +777,8 @@ static int usbduxfast_ai_insn_read(struct comedi_device *dev,
  	if (devpriv->ai_cmd_running) {
  		dev_err(dev->class_dev,
  			"ai_insn_read not possible, async cmd is running\n");
-		mutex_unlock(&devpriv->mut);
-		return -EBUSY;
+		ret = -EBUSY;
+		goto unlock;
  	}
/* set command for the first channel */
@@ -798,10 +798,8 @@ static int usbduxfast_ai_insn_read(struct comedi_device *dev,
  	usbduxfast_cmd_data(dev, 6, 0x01, 0x00, rngmask, 0x00);
ret = usbduxfast_send_cmd(dev, SENDADCOMMANDS);
-	if (ret < 0) {
-		mutex_unlock(&devpriv->mut);
-		return ret;
-	}
+	if (ret < 0)
+		goto unlock;
for (i = 0; i < PACKETS_TO_IGNORE; i++) {
  		ret = usb_bulk_msg(usb, usb_rcvbulkpipe(usb, BULKINEP),
@@ -809,8 +807,7 @@ static int usbduxfast_ai_insn_read(struct comedi_device *dev,
  				   &actual_length, 10000);
  		if (ret < 0) {
  			dev_err(dev->class_dev, "insn timeout, no data\n");
-			mutex_unlock(&devpriv->mut);
-			return ret;
+			goto unlock;
  		}
  	}
@@ -820,14 +817,13 @@ static int usbduxfast_ai_insn_read(struct comedi_device *dev,
  				   &actual_length, 10000);
  		if (ret < 0) {
  			dev_err(dev->class_dev, "insn data error: %d\n", ret);
-			mutex_unlock(&devpriv->mut);
-			return ret;
+			goto unlock;
  		}
  		n = actual_length / sizeof(u16);
  		if ((n % 16) != 0) {
  			dev_err(dev->class_dev, "insn data packet corrupted\n");
-			mutex_unlock(&devpriv->mut);
-			return -EINVAL;
+			ret = -EINVAL;
+			goto unlock;
  		}
  		for (j = chan; (j < n) && (i < insn->n); j = j + 16) {
  			data[i] = ((u16 *)(devpriv->inbuf))[j];
@@ -838,6 +834,10 @@ static int usbduxfast_ai_insn_read(struct comedi_device *dev,
  	mutex_unlock(&devpriv->mut);
return insn->n;

Minor niggle: You could also remove that call to mutex_unlock() by replacing the above three lines with:

	ret = insn->n;

which will fall through to the 'unlock:' label below.

+
+unlock:
+	mutex_unlock(&devpriv->mut);
+	return ret;
  }
static int usbduxfast_upload_firmware(struct comedi_device *dev,



--
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@xxxxxxxxx> )=-
-=(                          Web: http://www.mev.co.uk/  )=-
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