When I check hwrng attributes in sysfs, cat process always gets
stuck if guest has only 1 vcpu and uses a slow rng backend.
Currently we check if there is any tasks waiting to be run on
current cpu in rng_dev_read() by need_resched(). But need_resched()
doesn't work because rng_dev_read() is executing in user context.
This patch removed need_resched() and increase delay to 10 jiffies,
then other tasks can have chance to execute protected code.
Delaying 1 jiffy also works, but 10 jiffies is safer.
Signed-off-by: Amos Kong <akong@xxxxxxxxxx>
---
drivers/char/hw_random/core.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index c591d7e..b5d1b6f 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -195,8 +195,7 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf,
mutex_unlock(&rng_mutex);
- if (need_resched())
- schedule_timeout_interruptible(1);
+ schedule_timeout_interruptible(10);
if (signal_pending(current)) {
err = -ERESTARTSYS;
--
1.9.3
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