Hello,
Few days ago Alessio Igor Bogani<[email protected]> sent me patch
that removes BKLs like lock/unlock_kernel() in open call and place mutex
there in media/radio/radio-mr800.c.
This patch broke the driver, so we figured out new approah. We added one
more mutex lock that was used in open call. The patch is below:
diff -r ffa5df73ebeb linux/drivers/media/radio/radio-mr800.c
--- a/linux/drivers/media/radio/radio-mr800.c Fri Mar 13 00:43:34 2009
+0000
+++ b/linux/drivers/media/radio/radio-mr800.c Thu Apr 02 00:40:56 2009
+0400
@@ -163,6 +163,7 @@
unsigned char *buffer;
struct mutex lock; /* buffer locking */
+ struct mutex open;
int curfreq;
int stereo;
int users;
@@ -570,7 +571,7 @@
struct amradio_device *radio = video_get_drvdata(video_devdata(file));
int retval;
- lock_kernel();
+ mutex_lock(&radio->open);
radio->users = 1;
radio->muted = 1;
@@ -580,7 +581,7 @@
amradio_dev_warn(&radio->videodev->dev,
"radio did not start up properly\n");
radio->users = 0;
- unlock_kernel();
+ mutex_unlock(&radio->open);
return -EIO;
}
@@ -594,7 +595,7 @@
amradio_dev_warn(&radio->videodev->dev,
"set frequency failed\n");
- unlock_kernel();
+ mutex_unlock(&radio->open);
return 0;
}
@@ -735,6 +736,7 @@
radio->stereo = -1;
mutex_init(&radio->lock);
+ mutex_init(&radio->open);
video_set_drvdata(radio->videodev, radio);
retval = video_register_device(radio->videodev, VFL_TYPE_RADIO,
radio_nr);
I tested such approach using stress tool that tries to open /dev/radio0
few hundred times. Looks fine.
So, questions are:
1) What for is lock/unlock_kernel() used in open?
2) Can it be replaced by mutex, for example?
Please, comments, exaplanations are more than welcome.
Thanks,
--
best regards, Klimov Alexey
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