From mboxrd@z Thu Jan 1 00:00:00 1970 From: Amos Kong Subject: [PATCH 2/2] virtio-rng: fix stuck in catting hwrng attributes Date: Wed, 10 Sep 2014 17:07:07 +0800 Message-ID: <1410340027-15373-3-git-send-email-akong@redhat.com> References: <1410340027-15373-1-git-send-email-akong@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: amit.shah@redhat.com, kvm@vger.kernel.org To: virtualization@lists.linux-foundation.org Return-path: In-Reply-To: <1410340027-15373-1-git-send-email-akong@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Id: kvm.vger.kernel.org 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 --- 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