[PATCH] [rtl-sdr] Relaxed async state machine

[chris at techworks.ie]

From: Christian Gagneraud <chris at techworks.ie>

gr-osmosdr uses the driver in a multi-thread context, as a side effect the
cancel_async() can be called before read_async(), in such a case the cancel is
"forgotten".  This patch fixed that by being a bit more relaxed with
state machine transitions.
This patch doesn't fix any race conditions, it just make an anoying one less
likely to happen.

This patch goes along this one [1]

[1] http://lists.osmocom.org/pipermail/osmocom-sdr/2012-August/000201.html

Signed-off-by: Christian Gagneraud <chris at techworks.ie>
---
 src/librtlsdr.c |   10 +++++++---
 1 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/librtlsdr.c b/src/librtlsdr.c
index 4e54d8e..d83010d 100644
--- a/src/librtlsdr.c
+++ b/src/librtlsdr.c
@@ -1256,6 +1256,12 @@ int rtlsdr_read_async(rtlsdr_dev_t *dev, rtlsdr_read_async_cb_t cb, void *ctx,
 	if (!dev)
 		return -1;
 
+	/* It can happen if cancel_async is called before read_async */
+	if (dev->async_status != RTLSDR_INACTIVE)
+	    return -1;
+
+	dev->async_status = RTLSDR_RUNNING;
+
 	dev->cb = cb;
 	dev->cb_ctx = ctx;
 
@@ -1284,8 +1290,6 @@ int rtlsdr_read_async(rtlsdr_dev_t *dev, rtlsdr_read_async_cb_t cb, void *ctx,
 		libusb_submit_transfer(dev->xfer[i]);
 	}
 
-	dev->async_status = RTLSDR_RUNNING;
-
 	while (RTLSDR_INACTIVE != dev->async_status) {
 		r = libusb_handle_events_timeout(dev->ctx, &tv);
 		if (r < 0) {
@@ -1326,7 +1330,7 @@ int rtlsdr_cancel_async(rtlsdr_dev_t *dev)
 	if (!dev)
 		return -1;
 
-	if (RTLSDR_RUNNING == dev->async_status) {
+	if (RTLSDR_CANCELING != dev->async_status) {
 		dev->async_status = RTLSDR_CANCELING;
 		return 0;
 	}
-- 
1.7.7