K 10
svn:author
V 3
ken
K 8
svn:date
V 27
2003-09-10T00:40:40.000000Z
K 7
svn:log
V 2266
MFC:  Move dynamic sysctl(8) variable creation for the cd(4) and da(4)
drivers out of cdregister() and daregister(), which are run from interrupt
context.

Files/revisions merged:

scsi_da.c:		1.157, 1.158
scsi_cd.c:		1.81
subr_taskqueue.c:	1.17
taskqueue.h:		1.8
cd.4:			1.33
da.4:			1.42
cd.9:			1.18
not merged:		taskqueue.9 rev 1.7, 1.8 (not in RELENG_4)

This code is necessarily a little bit different than the version committed
to -current, mainly in the area of mutexes.  (Which become splfoo() in
-stable.)

The sysctl code does blocking mallocs (M_WAITOK), which causes problems
if malloc(9) actually needs to sleep.  (And causes a panic for people
running with INVARIANTS turned on.)

The eventual fix for this issue will involve moving the CAM probe process
inside a kernel thread.  For now, though, I have fixed the issue by moving
dynamic sysctl variable creation for these two drivers to a task queue
running in a kernel thread.

The existing task queue in -stable (taskqueue_swi) runs in software interrupt
handlers, which wouldn't fix the problem at hand.  So I have created a new
task queue, taskqueue_thread, that runs inside a kernel thread.

scsi_cd.c:	Remove sysctl variable creation code from cdregister(), and
		move it to a new function, cdsysctlinit().  Queue
		cdsysctlinit() to the taskqueue_thread taskqueue once we
		have fully registered the cd(4) driver instance.

scsi_da.c:	Remove sysctl variable creation code from daregister(), and
		move it to move it to a new function, dasysctlinit().
		Queue dasysctlinit() to the taskqueue_thread taskqueue once
		we have fully registered the da(4) instance.

taskqueue.h:	Declare the new taskqueue_thread taskqueue, update some
		comments.

subr_taskqueue.c:
		Create the new kernel thread taskqueue.

cd.4:		Update the cd(4) man page to talk about the minimum command
		size sysctl/loader tunable.  Also note that the changer
		variables are available as loader tunables as well.

da.4:		Update the da(4) man page to cover the retry_count,
		default_timeout and minimum_cmd_size sysctl variables/loader
		tunables.  Remove references to /dev/r???, they aren't used
		any longer.

cd.9:		Update the cd(9) man page to describe the CD_Q_10_BYTE_ONLY
		quirk.

Approved by:	re (scottl, murray)

END