[PATCH] nvme: Boot as soon as the boot controller has been probed

[Keith Busch]

On Wed, Nov 18, 2020 at 07:08:49PM -0800, Bart Van Assche wrote:
> On 11/12/20 6:20 AM, Keith Busch wrote:
> > The easiest check is something like this (as long as you're not actively
> > using your nvme namespaces):
> > 
> >   # echo 1 | tee /sys/class/nvme/nvme*/device/remove
> >   # echo 1 > /sys/bus/pci/rescan
> > 
> > The subsequent probes don't go through the async_schedule. They have
> > this stack instead:
> > 
> > [   44.528906] Call Trace:
> > [   44.530512]  dump_stack+0x6d/0x88
> > [   44.532373]  nvme_probe+0x2f/0x59b [nvme]
> > [   44.534466]  local_pci_probe+0x3d/0x70
> > [   44.536471]  pci_device_probe+0x107/0x1b0
> > [   44.538562]  really_probe+0x1be/0x410
> > [   44.540564]  driver_probe_device+0xe1/0x150
> > [   44.542733]  ? driver_allows_async_probing+0x50/0x50
> > [   44.545170]  bus_for_each_drv+0x7b/0xc0
> > [   44.547172]  __device_attach+0xeb/0x170
> > [   44.549163]  pci_bus_add_device+0x4a/0x70
> > [   44.551182]  pci_bus_add_devices+0x2c/0x70
> > [   44.553229]  pci_rescan_bus+0x25/0x30
> > [   44.555126]  rescan_store+0x61/0x90
> > [   44.556975]  kernfs_fop_write+0xcb/0x1b0
> > [   44.558940]  vfs_write+0xbe/0x200
> > [   44.560710]  ksys_write+0x5f/0xe0
> > [   44.562483]  do_syscall_64+0x2d/0x40
> > [   44.564354]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> Hi Keith,
> 
> Thanks for the feedback. I will look further into this but I wouldn't
> mind if someone else would come up with a solution before I have a
> solution ready.

I suppose you could just add the PROBE_PREFER_ASYNCHRONOUS probe_type,
and let nvme_probe() continue to attempt its own async initialization.