[PATCH] Staging: quatech_usb2: Convert eos semaphore to mutex

[PATCH] Staging: quatech_usb2: Convert eos semaphore to mutex

[Alessio Igor Bogani]

The eos semaphore is used as a mutex so replace it with a real mutex.

Signed-off-by: Alessio Igor Bogani <abogani@texware.it>
---
 drivers/staging/comedi/drivers/quatech_daqp_cs.c |   15 ++++++++-------
 1 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/staging/comedi/drivers/quatech_daqp_cs.c b/drivers/staging/comedi/drivers/quatech_daqp_cs.c
index 6e9f482..3076666 100644
--- a/drivers/staging/comedi/drivers/quatech_daqp_cs.c
+++ b/drivers/staging/comedi/drivers/quatech_daqp_cs.c
@@ -67,7 +67,7 @@ struct local_info_t {
 
 	enum { semaphore, buffer } interrupt_mode;
 
-	struct semaphore eos;
+	struct mutex eos;
 
 	struct comedi_device *dev;
 	struct comedi_subdevice *s;
@@ -238,7 +238,7 @@ static int daqp_ai_cancel(struct comedi_device *dev, struct comedi_subdevice *s)
 /* Interrupt handler
  *
  * Operates in one of two modes.  If local->interrupt_mode is
- * 'semaphore', just signal the local->eos semaphore and return
+ * 'semaphore', just signal the local->eos mutex and return
  * (one-shot mode).  Otherwise (continuous mode), read data in from
  * the card, transfer it to the buffer provided by the higher-level
  * comedi kernel module, and signal various comedi callback routines,
@@ -287,7 +287,7 @@ static enum irqreturn daqp_interrupt(int irq, void *dev_id)
 
 	case semaphore:
 
-		up(&local->eos);
+		mutex_unlock(&local->eos);
 		break;
 
 	case buffer:
@@ -401,8 +401,9 @@ static int daqp_ai_insn_read(struct comedi_device *dev,
 		return -1;
 	}
 
-	/* Make sure semaphore is blocked */
-	sema_init(&local->eos, 0);
+	mutex_init(&local->eos);
+	/* Make sure mutex is blocked */
+	mutex_lock(&local->eos);
 	local->interrupt_mode = semaphore;
 	local->dev = dev;
 	local->s = s;
@@ -413,9 +414,9 @@ static int daqp_ai_insn_read(struct comedi_device *dev,
 		outb(DAQP_COMMAND_ARM | DAQP_COMMAND_FIFO_DATA,
 		     dev->iobase + DAQP_COMMAND);
 
-		/* Wait for interrupt service routine to unblock semaphore */
+		/* Wait for interrupt service routine to unblock mutex */
 		/* Maybe could use a timeout here, but it's interruptible */
-		if (down_interruptible(&local->eos))
+		if (mutex_lock_interruptible(&local->eos))
 			return -EINTR;
 
 		data[i] = inb(dev->iobase + DAQP_FIFO);
-- 
1.7.0.4

Re: [PATCH] Staging: quatech_usb2: Convert eos semaphore to mutex

[Oliver Neukum]

Am Samstag, 15. Mai 2010 23:40:02 schrieb Alessio Igor Bogani:
> The eos semaphore is used as a mutex so replace it with a real mutex.

Documentation/mutex-design.txt states that a mutex must not be used
from within an interrupt handler. Is this outdated?

	Regards
		Oliver

Re: [PATCH] Staging: quatech_usb2: Convert eos semaphore to mutex

[Alessio Igor Bogani]

Hi Oliver,

2010/5/15 Oliver Neukum <oliver@neukum.org>:
> Am Samstag, 15. Mai 2010 23:40:02 schrieb Alessio Igor Bogani:
>> The eos semaphore is used as a mutex so replace it with a real mutex.
>
> Documentation/mutex-design.txt states that a mutex must not be used
> from within an interrupt handler. Is this outdated?

You are right. Simply I didn't see irqreturn_t return type in function
prototype.

Sorry for my mistake.

Ciao,
Alessio

Re: [PATCH] Staging: quatech_usb2: Convert eos semaphore to mutex

[Arjan van de Ven]

On Sun, 16 May 2010 00:08:30 +0200
Alessio Igor Bogani <abogani@texware.it> wrote:

> Hi Oliver,
> 
> 2010/5/15 Oliver Neukum <oliver@neukum.org>:
> > Am Samstag, 15. Mai 2010 23:40:02 schrieb Alessio Igor Bogani:
> >> The eos semaphore is used as a mutex so replace it with a real
> >> mutex.
> >
> > Documentation/mutex-design.txt states that a mutex must not be used
> > from within an interrupt handler. Is this outdated?
> 
> You are right. Simply I didn't see irqreturn_t return type in function
> prototype.
> 
> Sorry for my mistake.
> 

you might want to convert it to a completion....
that sounds more the usage model that the driver here is doing


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org

[PATCH] Staging: comedi: quatech_daqp_cs.c Replace eos semaphore with a completion.

[Alessio Igor Bogani]

Build tested only.

Signed-off-by: Alessio Igor Bogani <abogani@texware.it>
---
 drivers/staging/comedi/drivers/quatech_daqp_cs.c |   15 ++++++++-------
 1 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/staging/comedi/drivers/quatech_daqp_cs.c b/drivers/staging/comedi/drivers/quatech_daqp_cs.c
index 197c302..a91db6c 100644
--- a/drivers/staging/comedi/drivers/quatech_daqp_cs.c
+++ b/drivers/staging/comedi/drivers/quatech_daqp_cs.c
@@ -56,6 +56,8 @@ Devices: [Quatech] DAQP-208 (daqp), DAQP-308
 #include <pcmcia/cisreg.h>
 #include <pcmcia/ds.h>
 
+#include <linux/completion.h>
+
 /* Maximum number of separate DAQP devices we'll allow */
 #define MAX_DEV         4
 
@@ -67,7 +69,7 @@ struct local_info_t {
 
 	enum { semaphore, buffer } interrupt_mode;
 
-	struct semaphore eos;
+	struct completion eos;
 
 	struct comedi_device *dev;
 	struct comedi_subdevice *s;
@@ -238,7 +240,7 @@ static int daqp_ai_cancel(struct comedi_device *dev, struct comedi_subdevice *s)
 /* Interrupt handler
  *
  * Operates in one of two modes.  If local->interrupt_mode is
- * 'semaphore', just signal the local->eos semaphore and return
+ * 'semaphore', just signal the local->eos completion and return
  * (one-shot mode).  Otherwise (continuous mode), read data in from
  * the card, transfer it to the buffer provided by the higher-level
  * comedi kernel module, and signal various comedi callback routines,
@@ -287,7 +289,7 @@ static enum irqreturn daqp_interrupt(int irq, void *dev_id)
 
 	case semaphore:
 
-		up(&local->eos);
+		complete(&local->eos);
 		break;
 
 	case buffer:
@@ -401,8 +403,7 @@ static int daqp_ai_insn_read(struct comedi_device *dev,
 		return -1;
 	}
 
-	/* Make sure semaphore is blocked */
-	sema_init(&local->eos, 0);
+	init_completion(&local->eos);
 	local->interrupt_mode = semaphore;
 	local->dev = dev;
 	local->s = s;
@@ -413,9 +414,9 @@ static int daqp_ai_insn_read(struct comedi_device *dev,
 		outb(DAQP_COMMAND_ARM | DAQP_COMMAND_FIFO_DATA,
 		     dev->iobase + DAQP_COMMAND);
 
-		/* Wait for interrupt service routine to unblock semaphore */
+		/* Wait for interrupt service routine to unblock completion */
 		/* Maybe could use a timeout here, but it's interruptible */
-		if (down_interruptible(&local->eos))
+		if (wait_for_completion_interruptible(&local->eos))
 			return -EINTR;
 
 		data[i] = inb(dev->iobase + DAQP_FIFO);
-- 
1.7.0.4