[PATCH 2/7] staging: comedi: comedi_fops: eliminate a use of subdevice spin-lock

[Ian Abbott]

`comedi_is_subdevice_in_error()` is only used by `comedi_read()` and
`comedi_write()` and is only called (soon) after
`comedi_is_subdevice_running()` returns `false` (with extra conditions
in the case of `comedi_write()`).  `comedi_is_subdevice_running()` and
`comedi_get_subdevice_runflags()` both call
`comedi_get_subdevice_runflags()` which uses the subdevice's spin-lock.

Eliminate one use of the subdevice's spin-lock in `comedi_read()` and
`comedi_write()` by calling `comedi_get_subdevice_runflags()` and
checking the runflags directly.  Add a couple of inline functions to
check the runflags: `comedi_is_runflags_running()` and
`comedi_is_runflags_in_error()`.  These do the same test on runflags as
`comedi_is_subdevice_running()` and `comedi_is_subdevice_in_error()` but
get passed the runflags value directly.

`comedi_is_subdevice_in_error()` is no longer used, so remove it.

Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx>
---
 drivers/staging/comedi/comedi_fops.c | 32 ++++++++++++++++++++------------
 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index 2b75b7a1..17ac285 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -623,6 +623,16 @@ static unsigned comedi_get_subdevice_runflags(struct comedi_subdevice *s)
 	return runflags;
 }
 
+static bool comedi_is_runflags_running(unsigned runflags)
+{
+	return runflags & COMEDI_SRF_RUNNING;
+}
+
+static bool comedi_is_runflags_in_error(unsigned runflags)
+{
+	return runflags & COMEDI_SRF_ERROR;
+}
+
 /**
  * comedi_is_subdevice_running - check if async command running on subdevice
  * @s: comedi_subdevice struct
@@ -634,17 +644,10 @@ bool comedi_is_subdevice_running(struct comedi_subdevice *s)
 {
 	unsigned runflags = comedi_get_subdevice_runflags(s);
 
-	return (runflags & COMEDI_SRF_RUNNING) ? true : false;
+	return comedi_is_runflags_running(runflags);
 }
 EXPORT_SYMBOL_GPL(comedi_is_subdevice_running);
 
-static bool comedi_is_subdevice_in_error(struct comedi_subdevice *s)
-{
-	unsigned runflags = comedi_get_subdevice_runflags(s);
-
-	return (runflags & COMEDI_SRF_ERROR) ? true : false;
-}
-
 static bool comedi_is_subdevice_idle(struct comedi_subdevice *s)
 {
 	unsigned runflags = comedi_get_subdevice_runflags(s);
@@ -2282,13 +2285,16 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
 	add_wait_queue(&async->wait_head, &wait);
 	on_wait_queue = true;
 	while (nbytes > 0 && !retval) {
+		unsigned runflags;
+
 		set_current_state(TASK_INTERRUPTIBLE);
 
-		if (!comedi_is_subdevice_running(s)) {
+		runflags = comedi_get_subdevice_runflags(s);
+		if (!comedi_is_runflags_running(runflags)) {
 			if (count == 0) {
 				struct comedi_subdevice *new_s;
 
-				if (comedi_is_subdevice_in_error(s))
+				if (comedi_is_runflags_in_error(runflags))
 					retval = -EPIPE;
 				else
 					retval = 0;
@@ -2435,8 +2441,10 @@ static ssize_t comedi_read(struct file *file, char __user *buf, size_t nbytes,
 			n = m;
 
 		if (n == 0) {
-			if (!comedi_is_subdevice_running(s)) {
-				if (comedi_is_subdevice_in_error(s))
+			unsigned runflags = comedi_get_subdevice_runflags(s);
+
+			if (!comedi_is_runflags_running(runflags)) {
+				if (comedi_is_runflags_in_error(runflags))
 					retval = -EPIPE;
 				else
 					retval = 0;
-- 
2.1.4

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