On Sun, Jun 20, 2021 at 10:54:20PM +0900, Tetsuo Handa wrote:
> On 2021/06/20 11:44, Hillf Danton wrote:
> > Good craft in regard to triggering the ABBA deadlock, but curious why not
> > move unregister_blkdev out of and before loop_ctl_mutex, given it will also
> > serialise with the prober.
> >
>
> Well, something like this untested diff?
>
> Call unregister_blkdev() as soon as __exit function starts, for calling
> probe function after cleanup started will be unexpected for __exit function.
>
> Keep probe function no-op until __init function ends, for probe function
> might be called as soon as __register_blkdev() succeeded but calling probe
> function before setup completes will be unexpected for __init function.
>
> drivers/block/ataflop.c | 6 +++++-
> drivers/block/brd.c | 8 ++++++--
> drivers/block/floppy.c | 4 ++++
> drivers/block/loop.c | 4 ++--
> drivers/ide/ide-probe.c | 8 +++++++-
> drivers/md/md.c | 5 +++++
> drivers/scsi/sd.c | 10 +---------
> 7 files changed, 30 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c
> index d601e49f80e0..3681e8c493b1 100644
> --- a/drivers/block/ataflop.c
> +++ b/drivers/block/ataflop.c
> @@ -1995,6 +1995,7 @@ static int ataflop_alloc_disk(unsigned int drive, unsigned int type)
> }
>
> static DEFINE_MUTEX(ataflop_probe_lock);
> +static bool module_initialize_completed;
This is almost always wrong.
>
> static void ataflop_probe(dev_t dev)
> {
> @@ -2006,6 +2007,8 @@ static void ataflop_probe(dev_t dev)
>
> if (drive >= FD_MAX_UNITS || type >= NUM_DISK_MINORS)
> return;
> + if (!module_initialize_completed)
> + return;
This is not correct, when you register a callback structure, it can be
instantly called. Do not expect it to be delayed until later.
thanks,
greg k-h
