On Thu, 2024-04-18 at 15:36 +0800, Heng Qi wrote: > > 在 2024/4/18 下午2:42, Jason Wang 写道: > > On Wed, Apr 17, 2024 at 3:31 AM Daniel Jurgens <danielj@xxxxxxxxxx> wrote: > > > The command VQ will no longer be protected by the RTNL lock. Use a > > > spinlock to protect the control buffer header and the VQ. > > > > > > Signed-off-by: Daniel Jurgens <danielj@xxxxxxxxxx> > > > Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxx> > > > --- > > > drivers/net/virtio_net.c | 6 +++++- > > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > > > index 0ee192b45e1e..d02f83a919a7 100644 > > > --- a/drivers/net/virtio_net.c > > > +++ b/drivers/net/virtio_net.c > > > @@ -282,6 +282,7 @@ struct virtnet_info { > > > > > > /* Has control virtqueue */ > > > bool has_cvq; > > > + spinlock_t cvq_lock; > > Spinlock is instead of mutex which is problematic as there's no > > guarantee on when the driver will get a reply. And it became even more > > serious after 0d197a147164 ("virtio-net: add cond_resched() to the > > command waiting loop"). > > > > Any reason we can't use mutex? > > Hi Jason, > > I made a patch set to enable ctrlq's irq on top of this patch set, which > removes cond_resched(). > > But I need a little time to test, this is close to fast. So could the > topic about cond_resched + > spin lock or mutex lock be wait? The big problem is that until the cond_resched() is there, replacing the mutex with a spinlock can/will lead to scheduling while atomic splats. We can't intentionally introduce such scenario. Side note: the compiler apparently does not like guard() construct, leading to new warning, here and in later patches. I'm unsure if the code simplification is worthy. Cheers, Paolo