CVS commit: src/sys/miscfs/specfs

["Taylor R Campbell" <riastradh%netbsd.org@localhost>]

Module Name:    src
Committed By:   riastradh
Date:           Mon Mar 28 12:37:09 UTC 2022

Modified Files:
        src/sys/miscfs/specfs: spec_vnops.c specdev.h

Log Message:
specfs: Prevent new opens while close is waiting to drain.

Otherwise, bdev/cdev_close could have cancelled all _existing_ opens,
and waited for them to complete (and freed resources used by them) --
but a new one could start, and hang (e.g., a tty), at the same time
spec_close tries to drain all pending I/O operations, one of which
(the new open) is now hanging indefinitely.

Preventing the new open from even starting until bdev/cdev_close is
finished and all I/O operations have drained avoids this deadlock.


To generate a diff of this commit:
cvs rdiff -u -r1.203 -r1.204 src/sys/miscfs/specfs/spec_vnops.c
cvs rdiff -u -r1.49 -r1.50 src/sys/miscfs/specfs/specdev.h

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.