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Subject[PATCH 07/16] [media] radio-cadet: avoid interruptible_sleep_on race
Date
interruptible_sleep_on is racy and going away. This replaces
one use in the radio-cadet driver with an wait_event_interruptible
call that lets us check the condition under the mutex
but sleep without it.

The first version of this patch was done by Arnd, but Hans
came up with a nicer solution.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Mauro Carvalho Chehab <m.chehab@samsung.com>
Cc: linux-media@vger.kernel.org
---
drivers/media/radio/radio-cadet.c | 46 +++++++++++++++++++++++----------------
1 file changed, 27 insertions(+), 19 deletions(-)

diff --git a/drivers/media/radio/radio-cadet.c b/drivers/media/radio/radio-cadet.c
index 545c04c..d27e8b2 100644
--- a/drivers/media/radio/radio-cadet.c
+++ b/drivers/media/radio/radio-cadet.c
@@ -270,6 +270,16 @@ reset_rds:
outb(inb(dev->io + 1) & 0x7f, dev->io + 1);
}

+static bool cadet_has_rds_data(struct cadet *dev)
+{
+ bool result;
+
+ mutex_lock(&dev->lock);
+ result = dev->rdsin != dev->rdsout;
+ mutex_unlock(&dev->lock);
+ return result;
+}
+

static void cadet_handler(unsigned long data)
{
@@ -279,13 +289,12 @@ static void cadet_handler(unsigned long data)
if (mutex_trylock(&dev->lock)) {
outb(0x3, dev->io); /* Select RDS Decoder Control */
if ((inb(dev->io + 1) & 0x20) != 0)
- printk(KERN_CRIT "cadet: RDS fifo overflow\n");
+ pr_err("cadet: RDS fifo overflow\n");
outb(0x80, dev->io); /* Select RDS fifo */
+
while ((inb(dev->io) & 0x80) != 0) {
dev->rdsbuf[dev->rdsin] = inb(dev->io + 1);
- if (dev->rdsin + 1 == dev->rdsout)
- printk(KERN_WARNING "cadet: RDS buffer overflow\n");
- else
+ if (dev->rdsin + 1 != dev->rdsout)
dev->rdsin++;
}
mutex_unlock(&dev->lock);
@@ -294,7 +303,7 @@ static void cadet_handler(unsigned long data)
/*
* Service pending read
*/
- if (dev->rdsin != dev->rdsout)
+ if (cadet_has_rds_data(dev))
wake_up_interruptible(&dev->read_queue);

/*
@@ -327,22 +336,21 @@ static ssize_t cadet_read(struct file *file, char __user *data, size_t count, lo
mutex_lock(&dev->lock);
if (dev->rdsstat == 0)
cadet_start_rds(dev);
- if (dev->rdsin == dev->rdsout) {
- if (file->f_flags & O_NONBLOCK) {
- i = -EWOULDBLOCK;
- goto unlock;
- }
- mutex_unlock(&dev->lock);
- interruptible_sleep_on(&dev->read_queue);
- mutex_lock(&dev->lock);
- }
+ mutex_unlock(&dev->lock);
+
+ if (!cadet_has_rds_data(dev) && (file->f_flags & O_NONBLOCK))
+ return -EWOULDBLOCK;
+ i = wait_event_interruptible(dev->read_queue, cadet_has_rds_data(dev));
+ if (i)
+ return i;
+
+ mutex_lock(&dev->lock);
while (i < count && dev->rdsin != dev->rdsout)
readbuf[i++] = dev->rdsbuf[dev->rdsout++];
+ mutex_unlock(&dev->lock);

if (i && copy_to_user(data, readbuf, i))
- i = -EFAULT;
-unlock:
- mutex_unlock(&dev->lock);
+ return -EFAULT;
return i;
}

@@ -352,7 +360,7 @@ static int vidioc_querycap(struct file *file, void *priv,
{
strlcpy(v->driver, "ADS Cadet", sizeof(v->driver));
strlcpy(v->card, "ADS Cadet", sizeof(v->card));
- strlcpy(v->bus_info, "ISA", sizeof(v->bus_info));
+ strlcpy(v->bus_info, "ISA:radio-cadet", sizeof(v->bus_info));
v->device_caps = V4L2_CAP_TUNER | V4L2_CAP_RADIO |
V4L2_CAP_READWRITE | V4L2_CAP_RDS_CAPTURE;
v->capabilities = v->device_caps | V4L2_CAP_DEVICE_CAPS;
@@ -491,7 +499,7 @@ static unsigned int cadet_poll(struct file *file, struct poll_table_struct *wait
cadet_start_rds(dev);
mutex_unlock(&dev->lock);
}
- if (dev->rdsin != dev->rdsout)
+ if (cadet_has_rds_data(dev))
res |= POLLIN | POLLRDNORM;
return res;
}
--
1.8.3.2


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