diff options
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 | |
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')
-rw-r--r-- | share/man/man4/cd.4 | 37 | ||||
-rw-r--r-- | share/man/man4/da.4 | 96 | ||||
-rw-r--r-- | share/man/man9/cd.9 | 18 | ||||
-rw-r--r-- | share/man/man9/taskqueue.9 | 37 |
4 files changed, 132 insertions, 56 deletions
diff --git a/share/man/man4/cd.4 b/share/man/man4/cd.4 index 579fcea..7c491f5 100644 --- a/share/man/man4/cd.4 +++ b/share/man/man4/cd.4 @@ -25,7 +25,7 @@ .\" .\" $FreeBSD$ .\" -.Dd October 10, 1998 +.Dd September 2, 2003 .Dt CD 4 .Os .Sh NAME @@ -370,6 +370,37 @@ Some work is planned to support some of the more common `broken' .Tn CD-ROM drives; however, this is not yet under way. +.Pp +The +.Nm +driver attempts to automatically determine whether the drive it is talking +to supports 6 byte or 10 byte MODE SENSE/MODE SELECT operations. Many +.Tn SCSI +drives only support 6 byte commands, and +.Tn ATAPI +drives only support 10 byte commands. +The +.Nm +driver first attempts to determine whether the protocol in use typically +supports 6 byte commands by issuing a CAM Path Inquiry CCB. +It will then default to 6 byte or 10 byte commands as appropriate. +After that, the +.Nm +driver defaults to using 6 byte commands (assuming the protocol the drive +speaks claims to support 6 byte commands), until one fails with a +.Tn SCSI +ILLEGAL REQUEST error. Then it tries the 10 byte version of the command to +see if that works instead. Users can change the default via per-drive +sysctl variables and loader tunables. The variable names are the same in +both instances: +.Pp +.Va kern.cam.cd.%d.minimum_cmd_size +.Pp +Where +.Dq %d +is the unit number of the drive in question. Valid minimum command sizes +are 6 and 10. Any value above 6 will be rounded to 10, and any value below +6 will be rounded to 6. .Sh CHANGER OPERATION This driver has built-in support for LUN-based CD changers. A LUN-based CD @@ -399,7 +430,7 @@ If there is no outstanding I/O for another LUN, the driver will allow indefinite access to a given LUN. .Pp The minimum and maximum time quanta are configurable via kernel options and -also via sysctl variables. +also via sysctl and kernel tunable variables. The kernel options are: .Pp .Bl -item -compact @@ -409,7 +440,7 @@ The kernel options are: .Cd "options ""CHANGER_MAX_BUSY_SECONDS=11""" .El .Pp -The sysctl variables are: +The sysctl/kernel tunable variables are: .Pp .Bl -item -compact .It diff --git a/share/man/man4/da.4 b/share/man/man4/da.4 index 835f4fd..c35b59f 100644 --- a/share/man/man4/da.4 +++ b/share/man/man4/da.4 @@ -25,7 +25,7 @@ .\" .\" $FreeBSD$ .\" -.Dd October 15, 1998 +.Dd September 2, 2003 .Dt DA 4 .Os .Sh NAME @@ -196,6 +196,59 @@ The driver .Em will write the new disklabel to the disk. .El +.Sh SYSCTL VARIABLES +The following variables are available as both +.Xr sysctl 8 +variables and +.Xr loader 8 +tunables: +.Bl -tag -width 12 +.It kern.cam.da.retry_count +.Pp +This variable determines how many times the +.Nm +driver will retry a READ or WRITE command. +This does not affect the number of retries used during probe time or for +the +.Nm +driver dump routine. +This value currently defaults to 4. +.It kern.cam.da.default_timeout +.Pp +This variable determines how long the +.Nm +driver will wait before timing out an outstanding command. +The units for this value are seconds, and the default is currently 60 +seconds. +.It kern.cam.da.%d.minimum_cmd_size +.Pp +This variable determines what the minimum READ/WRITE CDB size is for a +given +.Nm +unit. +(The %d above denotes the unit number of the +.Nm +driver instance, e.g. 1, 2, 4, 8, etc.) +Valid minimum command size values are 6, 10, 12 and 16 bytes. +The default is 6 bytes. +.Pp +The +.Nm +driver issues a CAM Path Inquiry CCB at probe time to determine whether the +protocol the device in question speaks (e.g. ATAPI) typically doesn't allow +6 byte commands. +If it doesn't, the +.Nm +driver will default to using at least 10 byte CDBs. +If a 6 byte READ or WRITE fails with an ILLEGAL REQUEST error, the +.Nm +driver will then increase the default CDB size for the device to 10 bytes and +retry the command. +CDB size is always +chosen as the smallest READ/WRITE CDB that will satisfy the specified minimum +command size, and the LBA and length of the READ or WRITE in question. +(e.g., a write to an LBA larger than 2^32 will require a 16 byte CDB.) +.El .Sh NOTES If a device becomes invalidated (media is removed, device becomes unresponsive) the disklabel and information held within the kernel about the device will @@ -206,25 +259,9 @@ the last file descriptor referencing the old device is closed. During this period, all new open attempts will be rejected. .Sh FILES .Bl -tag -width /dev/rsdXXXXX -compact -.It Pa /dev/rda Ns Ar u -raw mode -.Tn SCSI -disk unit -.Ar u , -accessed as an unpartitioned device .Sm off .It Pa /dev/da Ar u Pa s Ar n .Sm on -block mode -.Tn SCSI -disk unit -.Ar u , -slice -.Ar n , -accessed as an unpartitioned device -.Sm off -.It Pa /dev/rda Ar u Pa s Ar n -.Sm on raw mode .Tn SCSI disk unit @@ -233,15 +270,6 @@ slice .Ar n , accessed as an unpartitioned device .It Pa /dev/da Ns Ar u Ns Ar p -block mode -.Tn SCSI -disk unit -.Ar u , -first -.Fx -slice, partition -.Ar p -.It Pa /dev/rda Ns Ar u Ns Ar p raw mode .Tn SCSI disk unit @@ -259,22 +287,6 @@ slice, partition .Ar p .Xc .Sm on -block mode -.Tn SCSI -disk unit -.Ar u , -.Ar n Ns th -slice, partition -.Ar p -.Sm off -.It Xo -.Pa /dev/rda -.Ar u -.Pa s -.Ar n -.Ar p -.Xc -.Sm on raw mode .Tn SCSI disk unit 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 diff --git a/share/man/man9/taskqueue.9 b/share/man/man9/taskqueue.9 index 013f737..7d35458 100644 --- a/share/man/man9/taskqueue.9 +++ b/share/man/man9/taskqueue.9 @@ -174,26 +174,43 @@ argument to the macro is executed as a C statement, allowing any further initialisation to be performed (such as registering an interrupt handler etc.) .Pp -The system provides a global taskqueue, +The system provides three global taskqueues, .Va taskqueue_swi , -which is run via a software interrupt mechanism. -To use this queue, +.Va taskqueue_swi_giant , +and +.Va taskqueue_thread . +The swi taskqueues are run via a software interrupt mechanism. +The taskqueue_swi queue runs without the protection of the Giant kernel lock, +and the taskqueue_swi_giant queue runs with the protection of the Giant +kernel lock. +The thread taskqueue runs in a kernel thread context, and tasks run from +this thread do not run under the Giant kernel lock. +If the caller wants to run under Giant, he should explicitly acquire and +release Giant in his taskqueue handler routine. + +To use these queues, call .Fn taskqueue_enqueue -with the value of the global variable -.Va taskqueue_swi . -The queue will be run at -.\" XXX This should be a cross-reference (Xr), but there is no MANLINKS -.\" entry for splsofttq.9 yet. -.Fn splsofttq . +with the value of the global taskqueue variable for the queue you wish to +use ( +.Va taskqueue_swi , +.Va taskqueue_swi_giant , +or +.Va taskqueue_thread +). .Pp -This queue can be used, +This the software interrupt queues can be used, for instance, for implementing interrupt handlers which must perform a significant amount of processing in the handler. The hardware interrupt handler would perform minimal processing of the interrupt and then enqueue a task to finish the work. This reduces to a minimum the amount of time spent with interrupts disabled. +.Pp +The thread queue can be used, for instance, by interrupt level routines +that need to call kernel functions that do things that can only be done +from a thread context. +(e.g., call malloc with the M_WAITOK flag.) .Sh HISTORY This interface first appeared in .Fx 5.0 . |