Re: [PATCH v2] block: genhd: don't call probe function with major_names_lock held

On 2021/06/20 11:44, Hillf Danton wrote:

quoted

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;

 
 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;