Re: [PATCH 2/2] virtio-rng: fix stuck in catting hwrng attributes

On Thu, Sep 11, 2014 at 11:38:38AM +0530, Amit Shah wrote:

On (Wed) 10 Sep 2014 [17:07:07], Amos Kong wrote:

quoted

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.

Hi Amit,
 

I'd prefer two patches for this one: one to remove the need_resched()
check, and the other to increase the timeout.

If Rusty agrees with this fix, I will respin to update the commitlog
with clear description and split the patches to 3.

Thanks for the review.
 

Anyway,

Reviewed-by: Amit Shah <redacted>

--
                Amos.