| Message ID | 20210606132909.177640-1-gdawar.xilinx@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | vhost-vdpa: log warning message if vhost_vdpa_remove gets blocked | expand |
在 2021/6/6 下午9:29, Gautam Dawar 写道: > From: Gautam Dawar <gdawar@xilinx.com> > > If some module invokes vdpa_device_unregister (usually in the module > unload function) when the userspace app (eg. QEMU) which had opened > the vhost-vdpa character device is still running, vhost_vdpa_remove() > function will block indefinitely in call to wait_for_completion(). > > This causes the vdpa_device_unregister caller to hang and with a > usual side-effect of rmmod command not returning when this call > is in the module_exit function. > > This patch converts the wait_for_completion call to its timeout based > counterpart (wait_for_completion_timeout) and also adds a warning > message to alert the user/administrator about this hang situation. > > To eventually fix this problem, a mechanism will be required to let > vhost-vdpa module inform the userspace of this situation and > userspace will close the descriptor of vhost-vdpa char device. > This will enable vhost-vdpa to continue with graceful clean-up. > > Signed-off-by: Gautam Dawar <gdawar@xilinx.com> > --- > drivers/vhost/vdpa.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c > index bfa4c6ef554e..572b64d09b06 100644 > --- a/drivers/vhost/vdpa.c > +++ b/drivers/vhost/vdpa.c > @@ -1091,7 +1091,11 @@ static void vhost_vdpa_remove(struct vdpa_device *vdpa) > opened = atomic_cmpxchg(&v->opened, 0, 1); > if (!opened) > break; > - wait_for_completion(&v->completion); > + wait_for_completion_timeout(&v->completion, > + msecs_to_jiffies(1000)); > + dev_warn_ratelimited(&v->dev, > + "%s waiting for /dev/%s to be closed\n", > + __func__, dev_name(&v->dev)); > } while (1); > > put_device(&v->dev); Acked-by: Jason Wang <jasowang@redhat.com>
On Tue, Jun 15, 2021 at 10:33:22PM +0800, Jason Wang wrote: > > 在 2021/6/6 下午9:29, Gautam Dawar 写道: > > From: Gautam Dawar <gdawar@xilinx.com> > > > > If some module invokes vdpa_device_unregister (usually in the module > > unload function) when the userspace app (eg. QEMU) which had opened > > the vhost-vdpa character device is still running, vhost_vdpa_remove() > > function will block indefinitely in call to wait_for_completion(). > > > > This causes the vdpa_device_unregister caller to hang and with a > > usual side-effect of rmmod command not returning when this call > > is in the module_exit function. > > > > This patch converts the wait_for_completion call to its timeout based > > counterpart (wait_for_completion_timeout) and also adds a warning > > message to alert the user/administrator about this hang situation. > > > > To eventually fix this problem, a mechanism will be required to let > > vhost-vdpa module inform the userspace of this situation and > > userspace will close the descriptor of vhost-vdpa char device. > > This will enable vhost-vdpa to continue with graceful clean-up. > > > > Signed-off-by: Gautam Dawar <gdawar@xilinx.com> > > --- > > drivers/vhost/vdpa.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c > > index bfa4c6ef554e..572b64d09b06 100644 > > --- a/drivers/vhost/vdpa.c > > +++ b/drivers/vhost/vdpa.c > > @@ -1091,7 +1091,11 @@ static void vhost_vdpa_remove(struct vdpa_device *vdpa) > > opened = atomic_cmpxchg(&v->opened, 0, 1); > > if (!opened) > > break; > > - wait_for_completion(&v->completion); > > + wait_for_completion_timeout(&v->completion, > > + msecs_to_jiffies(1000)); > > + dev_warn_ratelimited(&v->dev, > > + "%s waiting for /dev/%s to be closed\n", > > + __func__, dev_name(&v->dev)); Can fill up the kernel log in this case ... dev_warn_once seems more appropriate. > > } while (1); > > put_device(&v->dev); > > > Acked-by: Jason Wang <jasowang@redhat.com> >
Pls see inline [GD>>] -----Original Message----- From: Michael S. Tsirkin <mst@redhat.com> Sent: Saturday, July 3, 2021 1:42 PM To: Jason Wang <jasowang@redhat.com> Cc: Gautam Dawar <gdawar.xilinx@gmail.com>; Martin Petrus Hubertus Habets <martinh@xilinx.com>; Harpreet Singh Anand <hanand@xilinx.com>; Gautam Dawar <gdawar@xilinx.com>; kvm@vger.kernel.org; virtualization@lists.linux-foundation.org; netdev@vger.kernel.org; linux-kernel@vger.kernel.org Subject: Re: [PATCH] vhost-vdpa: log warning message if vhost_vdpa_remove gets blocked On Tue, Jun 15, 2021 at 10:33:22PM +0800, Jason Wang wrote: > > 在 2021/6/6 下午9:29, Gautam Dawar 写道: > > From: Gautam Dawar <gdawar@xilinx.com> > > > > If some module invokes vdpa_device_unregister (usually in the module > > unload function) when the userspace app (eg. QEMU) which had opened > > the vhost-vdpa character device is still running, > > vhost_vdpa_remove() function will block indefinitely in call to wait_for_completion(). > > > > This causes the vdpa_device_unregister caller to hang and with a > > usual side-effect of rmmod command not returning when this call is > > in the module_exit function. > > > > This patch converts the wait_for_completion call to its timeout > > based counterpart (wait_for_completion_timeout) and also adds a > > warning message to alert the user/administrator about this hang situation. > > > > To eventually fix this problem, a mechanism will be required to let > > vhost-vdpa module inform the userspace of this situation and > > userspace will close the descriptor of vhost-vdpa char device. > > This will enable vhost-vdpa to continue with graceful clean-up. > > > > Signed-off-by: Gautam Dawar <gdawar@xilinx.com> > > --- > > drivers/vhost/vdpa.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c index > > bfa4c6ef554e..572b64d09b06 100644 > > --- a/drivers/vhost/vdpa.c > > +++ b/drivers/vhost/vdpa.c > > @@ -1091,7 +1091,11 @@ static void vhost_vdpa_remove(struct vdpa_device *vdpa) > > opened = atomic_cmpxchg(&v->opened, 0, 1); > > if (!opened) > > break; > > - wait_for_completion(&v->completion); > > + wait_for_completion_timeout(&v->completion, > > + msecs_to_jiffies(1000)); > > + dev_warn_ratelimited(&v->dev, > > + "%s waiting for /dev/%s to be closed\n", > > + __func__, dev_name(&v->dev)); Can fill up the kernel log in this case ... dev_warn_once seems more appropriate. [GD>>] Submitted the patch with suggested modification. > > } while (1); > > put_device(&v->dev); > > > Acked-by: Jason Wang <jasowang@redhat.com> >
diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c index bfa4c6ef554e..572b64d09b06 100644 --- a/drivers/vhost/vdpa.c +++ b/drivers/vhost/vdpa.c @@ -1091,7 +1091,11 @@ static void vhost_vdpa_remove(struct vdpa_device *vdpa) opened = atomic_cmpxchg(&v->opened, 0, 1); if (!opened) break; - wait_for_completion(&v->completion); + wait_for_completion_timeout(&v->completion, + msecs_to_jiffies(1000)); + dev_warn_ratelimited(&v->dev, + "%s waiting for /dev/%s to be closed\n", + __func__, dev_name(&v->dev)); } while (1); put_device(&v->dev);