CVS commit: src/sys/dev/acpi

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

Module Name:    src
Committed By:   riastradh
Date:           Fri Aug 12 16:21:41 UTC 2022

Modified Files:
        src/sys/dev/acpi: thinkpad_acpi.c

Log Message:
thinkpad(4): Don't detach on shutdown.

There's no important state that needs to be recorded, or resources
that need to be relinquished, so detach-on-shutdown isn't necessary.

At the moment, detach-on-shutdown is actually harmful here: if
shutdown is triggered by a sysmon power switch event, then
config_detach will be called from the sysmon taskqueue, but
thinkpad_detach has to wait for ACPI notifiers to finish running
which means waiting for the sysmon taskqueue -> deadlock or crash.

We should maybe arrange to do config_detach from a thread other than
the sysmon taskqueue thread to avoid this class of problems -- but
for now, thinkpad(4) has no reason to detach on shutdown anyway, so
let's take the easy path.

Note: There are many drivers that set DVF_DETACH_SHUTDOWN which
probably shouldn't; the flag means the kernel _will_ detach on
shutdown, not that it _may_.  Even those that do need to record state
or relinquish resources might be better served by pmf shutdown hooks
which can skip freeing software resources for faster shutdown.


To generate a diff of this commit:
cvs rdiff -u -r1.54 -r1.55 src/sys/dev/acpi/thinkpad_acpi.c

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