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From: Amos Kong <akong@redhat.com>
To: Amit Shah <amit.shah@redhat.com>
Cc: herbert.xu@redhat.com, kvm@vger.kernel.org,
	virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 2/2] virtio-rng: fix stuck in catting hwrng attributes
Date: Sun, 14 Sep 2014 09:16:17 +0800	[thread overview]
Message-ID: <20140914011617.GB1032@zen.redhat.com> (raw)
In-Reply-To: <20140911060838.GF19202@grmbl.mre>

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

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 <amit.shah@redhat.com>

--
                Amos.

  reply	other threads:[~2014-09-14  1:16 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-10  9:07 [PATCH 0/2] fix stuck in catting hwrng attributes Amos Kong
2014-09-10  9:07 ` [PATCH 1/2] virtio-rng cleanup: move some code out of mutex protection Amos Kong
2014-09-11  6:07   ` Amit Shah
2014-09-10  9:07 ` [PATCH 2/2] virtio-rng: fix stuck in catting hwrng attributes Amos Kong
2014-09-11  6:08   ` Amit Shah
2014-09-14  1:16     ` Amos Kong [this message]
2014-09-11 11:38   ` Rusty Russell
2014-09-13 17:12     ` Amos Kong
2014-09-14  1:12       ` Amos Kong
2014-09-14  2:25         ` Amos Kong
2014-09-15 16:48           ` Radim Krčmář
2014-09-16  0:50             ` Amos Kong
2014-09-16  0:50               ` Amos Kong
2014-09-16 15:35         ` Rusty Russell

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