* Vivek Goyal (vgo...@redhat.com) wrote:
> On Tue, Nov 26, 2019 at 01:02:29PM +0000, Dr. David Alan Gilbert wrote:
>
> [..]
> > > > > @@ -1950,21 +1948,54 @@ static void lo_setlk(fuse_req_t req,
> > > > > fuse_ino_t ino,
> > > > >
> > > > > if (!plock) {
> > > > > saverr = ret;
> > > > > + pthread_mutex_unlock(&inode->plock_mutex);
> > > > > goto out;
> > > > > }
> > > > >
> > > > > + /*
> > > > > + * plock is now released when inode is going away. We already
> > > > > have
> > > > > + * a reference on inode, so it is guaranteed that plock->fd is
> > > > > + * still around even after dropping inode->plock_mutex lock
> > > > > + */
> > > > > + ofd = plock->fd;
> > > > > + pthread_mutex_unlock(&inode->plock_mutex);
> > > > > +
> > > > > + /*
> > > > > + * If this lock request can block, request caller to wait for
> > > > > + * notification. Do not access req after this. Once lock is
> > > > > + * available, send a notification instead.
> > > > > + */
> > > > > + if (sleep && lock->l_type != F_UNLCK) {
> > > > > + /*
> > > > > + * If notification queue is not enabled, can't support
> > > > > async
> > > > > + * locks.
> > > > > + */
> > > > > + if (!se->notify_enabled) {
> > > > > + saverr = EOPNOTSUPP;
> > > > > + goto out;
> > > > > + }
> > > > > + async_lock = true;
> > > > > + unique = req->unique;
> > > > > + fuse_reply_wait(req);
> > > > > + }
> > > > > /* TODO: Is it alright to modify flock? */
> > > > > lock->l_pid = 0;
> > > > > - ret = fcntl(plock->fd, F_OFD_SETLK, lock);
> > > > > + if (async_lock)
> > > > > + ret = fcntl(ofd, F_OFD_SETLKW, lock);
> > > > > + else
> > > > > + ret = fcntl(ofd, F_OFD_SETLK, lock);
> > > >
> > > > What happens if the guest is rebooted after it's asked
> > > > for, but not been granted a lock?
> > >
> > > I think a regular reboot can't be done till a request is pending, because
> > > virtio-fs can't be unmounted and unmount will wait for all pending
> > > requests to finish.
> > >
> > > Destroying qemu will destroy deamon too.
> > >
> > > Are there any other reboot paths I have missed.
> >
> > Yes, there are a few other ways the guest can reboot:
> > a) A echo b > /proc/sysrq-trigger
>
> I tried it. Both qemu and virtiofsd hang. virtiofsd wants to stop a
> queue. And that tries to stop thrad pool. But one of the threads in
> thread pool is blocked on setlkw. So g_thread_pool_free() hangs.
>
> I am not seeing any option in glib thread pool API to stop or send
> signal to threads which are blocked.
Is there a way to setup pthread_cancel ? The upstream libfuse code
has somec ases where it enables cancellation very carefully around
something that might block, does it, then disables cancellation.
Dave
> Thanks
> Vivek
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
