CVS commit: src/sys

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

Module Name:    src
Committed By:   riastradh
Date:           Mon Mar 28 12:38:15 UTC 2022

Modified Files:
        src/sys/kern: subr_autoconf.c
        src/sys/sys: device.h

Log Message:
autoconf(9): New function config_detach_commit.

When a driver's .ca_detach function has committed to detaching -- it
definitely won't back out with EBUSY, for instance -- it can call
this to wake all pending calls to device_lookup_acquire and make them
fail immediately.

This is necessary to break a deadlock if the device_lookup_acquire
calls happen inside I/O operations which the driver's .ca_detach
function waits for the completion of -- without config_detach_commit,
I/O operations would be stuck in device_lookup_acquire waiting for
.ca_detach and .ca_detach would be stuck waiting for I/O operations
to return.

Most drivers won't need to call this: for autoconf drivers used the
traditional way by devsw for userland device nodes, the .ca_detach
routine uses vdevgone, and we will arrange to make vdevgone call
config_detach_commit automagically in such drivers anyway.

XXX kernel ABI change to struct device requires bump -- later change
will make struct device opaque to ABI, but we're not there yet


To generate a diff of this commit:
cvs rdiff -u -r1.298 -r1.299 src/sys/kern/subr_autoconf.c
cvs rdiff -u -r1.180 -r1.181 src/sys/sys/device.h

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