Re: [PATCH 2/2] virtio-rng: fix stuck in catting hwrng attributes
From: Amit Shah <hidden>
Date: 2014-09-11 06:08:38
Also in:
kvm
On (Wed) 10 Sep 2014 [17:07:07], Amos Kong wrote:
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.
I'd prefer two patches for this one: one to remove the need_resched() check, and the other to increase the timeout. Anyway, Reviewed-by: Amit Shah <redacted>
quoted hunk ↗ jump to hunk
Signed-off-by: Amos Kong <redacted> --- 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
Amit