Hi Amit, Rusty
RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1127062
steps:
- Read random data by 'dd if=/dev/hwrng of=/dev/null' in guest
- check sysfs files in the same time, 'cat /sys/class/misc/hw_random/rng_*'
Result: cat process will get stuck, it will return if we kill dd process.
We have some static variables (eg, current_rng, data_avail, etc) in
hw_random/core.c,
they are protected by rng_mutex. I try to workaround this issue by undelay(100)
after mutex_unlock() in rng_dev_read(). This gives chance for
hwrng_attr_*_show()
to get mutex.
This patch also contains some cleanup, moving some code out of mutex
protection.
Do you have some suggestion? Thanks.
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index aa30a25..fa69020 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -194,6 +194,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user
*buf,
}
mutex_unlock(&rng_mutex);
+ udelay(100);
if (need_resched())
schedule_timeout_interruptible(1);
@@ -233,10 +234,10 @@ static ssize_t hwrng_attr_current_store(struct device
*dev,
int err;
struct hwrng *rng;
+ err = -ENODEV;
err = mutex_lock_interruptible(&rng_mutex);
if (err)
return -ERESTARTSYS;
- err = -ENODEV;
list_for_each_entry(rng, &rng_list, list) {
if (strcmp(rng->name, buf) == 0) {
if (rng == current_rng) {
@@ -270,8 +271,8 @@ static ssize_t hwrng_attr_current_show(struct device *dev,
return -ERESTARTSYS;
if (current_rng)
name = current_rng->name;
- ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
mutex_unlock(&rng_mutex);
+ ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
return ret;
}
@@ -284,19 +285,19 @@ static ssize_t hwrng_attr_available_show(struct device
*dev,
ssize_t ret = 0;
struct hwrng *rng;
+ buf[0] = '\0';
err = mutex_lock_interruptible(&rng_mutex);
if (err)
return -ERESTARTSYS;
- buf[0] = '\0';
list_for_each_entry(rng, &rng_list, list) {
strncat(buf, rng->name, PAGE_SIZE - ret - 1);
ret += strlen(rng->name);
strncat(buf, " ", PAGE_SIZE - ret - 1);
ret++;
}
+ mutex_unlock(&rng_mutex);
strncat(buf, "\n", PAGE_SIZE - ret - 1);
ret++;
- mutex_unlock(&rng_mutex);
return ret;
}
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
