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author | ken <ken@FreeBSD.org> | 2003-09-03 04:46:28 +0000 |
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committer | ken <ken@FreeBSD.org> | 2003-09-03 04:46:28 +0000 |
commit | 03d0445c1692534218893d0f76a5232a12769935 (patch) | |
tree | 54485ba0616eea8f013a6221f95c3b93a70168ce /share/man/man9/cd.9 | |
parent | 96db6adb01216f8a587311123b15f9ae3c246431 (diff) | |
download | FreeBSD-src-03d0445c1692534218893d0f76a5232a12769935.zip FreeBSD-src-03d0445c1692534218893d0f76a5232a12769935.tar.gz |
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.
The sysctl code does blocking mallocs (M_WAITOK), which causes problems
if malloc(9) actually needs to sleep.
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 queues (taskqueue_swi and taskqueue_swi_giant) run 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. (It also runs outside of Giant -- clients must explicitly acquire
and release Giant in their taskqueue functions.)
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. This taskqueue
runs outside of Giant, so any functions queued to it would
need to explicitly acquire/release Giant if they need it.
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.
taskqueue.9: Update the taskqueue(9) man page to describe the new thread
task queue, and the taskqueue_swi_giant queue.
MFC after: 3 days
Diffstat (limited to 'share/man/man9/cd.9')
-rw-r--r-- | share/man/man9/cd.9 | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/share/man/man9/cd.9 b/share/man/man9/cd.9 index 036fc80..49c2ede 100644 --- a/share/man/man9/cd.9 +++ b/share/man/man9/cd.9 @@ -27,7 +27,7 @@ .\" .\" $FreeBSD$ .\" -.Dd October 10, 1998 +.Dd September 2, 2003 .Dt CD 9 .Os .Sh NAME @@ -74,6 +74,22 @@ In general, the driver will figure this out automatically when it sees a LUN greater than 0. Setting this flag only has the effect of telling the driver to run the initial read capacity command for LUN 0 of the changer through the changer scheduling code. +.It Dv CD_Q_10_BYTE_ONLY +This flag tells the driver that the given device only accepts 10 byte MODE +SENSE/MODE SELECT commands. In general these types of quirks should not be +added to the +.Xr cd 4 +driver. The reason is that the driver does several things to attempt to +determine whether the drive in question needs 10 byte commands. First, it +issues a CAM Path Inquiry command to determine whether the protocol that +the drive speaks typically only allows 10 byte commands. (ATAPI and USB +are two prominent examples of protocols where you generally only want to +send 10 byte commands.) Then, if it gets an ILLEGAL REQUEST error back +from a 6 byte MODE SENSE or MODE SELECT command, it attempts to send the 10 +byte version of the command instead. The only reason you would need a +quirk is if your drive uses a protocol (e.g. +.Tn SCSI ) +that typically doesn't have a problem with 6 byte commands. .El .Sh FILES .Bl -tag -width /sys/cam/scsi/scsi_cd.c -compact |