K 10
svn:author
V 3
ian
K 8
svn:date
V 27
2019-05-15T17:50:17.216734Z
K 7
svn:log
V 596
MFC r347422:

Allow dcons(4) to be unloaded when loaded as a module.

When the module is unloaded, the tty devices are destroyed.  That requires
implementing the tsw_free callback to avoid a panic.  This driver requires
no particular cleanup to be done from the callback, but the module itself
must remain in memory until the deferred tsw_free callbacks are invoked.
These changes implement that by incrementing a reference count variable in
the detach routine, and decrementing it in the tsw_free callback.  The
MOD_UNLOAD event handler doesn't return until the count drops to zero.

PR: 237758

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