1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
|
/*
* scsi_queue.c Copyright (C) 1997 Eric Youngdale
*
* generic mid-level SCSI queueing.
*
* The point of this is that we need to track when hosts are unable to
* accept a command because they are busy. In addition, we track devices
* that cannot accept a command because of a QUEUE_FULL condition. In both
* of these cases, we enter the command in the queue. At some later point,
* we attempt to remove commands from the queue and retry them.
*/
#define __NO_VERSION__
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/malloc.h>
#include <linux/ioport.h>
#include <linux/kernel.h>
#include <linux/stat.h>
#include <linux/blk.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/smp_lock.h>
#define __KERNEL_SYSCALLS__
#include <linux/unistd.h>
#include <asm/system.h>
#include <asm/irq.h>
#include <asm/dma.h>
#include "scsi.h"
#include "hosts.h"
#include "constants.h"
/*
* TODO:
* 1) Prevent multiple traversals of list to look for commands to
* queue.
* 2) Protect against multiple insertions of list at the same time.
* DONE:
* 1) Set state of scsi command to a new state value for ml queue.
* 2) Insert into queue when host rejects command.
* 3) Make sure status code is properly passed from low-level queue func
* so that internal_cmnd properly returns the right value.
* 4) Insert into queue when QUEUE_FULL.
* 5) Cull queue in bottom half handler.
* 6) Check usage count prior to queue insertion. Requeue if usage
* count is 0.
* 7) Don't send down any more commands if the host/device is busy.
*/
static const char RCSid[] = "$Header: /mnt/ide/home/eric/CVSROOT/linux/drivers/scsi/scsi_queue.c,v 1.1 1997/10/21 11:16:38 eric Exp $";
/*
* Function: scsi_mlqueue_insert()
*
* Purpose: Insert a command in the midlevel queue.
*
* Arguments: cmd - command that we are adding to queue.
* reason - why we are inserting command to queue.
*
* Lock status: Assumed that lock is not held upon entry.
*
* Returns: Nothing.
*
* Notes: We do this for one of two cases. Either the host is busy
* and it cannot accept any more commands for the time being,
* or the device returned QUEUE_FULL and can accept no more
* commands.
* Notes: This could be called either from an interrupt context or a
* normal process context.
*/
int scsi_mlqueue_insert(Scsi_Cmnd * cmd, int reason)
{
struct Scsi_Host *host;
SCSI_LOG_MLQUEUE(1, printk("Inserting command %p into mlqueue\n", cmd));
/*
* We are inserting the command into the ml queue. First, we
* cancel the timer, so it doesn't time out.
*/
scsi_delete_timer(cmd);
host = cmd->host;
/*
* Next, set the appropriate busy bit for the device/host.
*/
if (reason == SCSI_MLQUEUE_HOST_BUSY) {
/*
* Protect against race conditions. If the host isn't busy,
* assume that something actually completed, and that we should
* be able to queue a command now. Note that there is an implicit
* assumption that every host can always queue at least one command.
* If a host is inactive and cannot queue any commands, I don't see
* how things could possibly work anyways.
*/
if (host->host_busy == 0) {
if (scsi_retry_command(cmd) == 0) {
return 0;
}
}
host->host_blocked = TRUE;
} else {
/*
* Protect against race conditions. If the device isn't busy,
* assume that something actually completed, and that we should
* be able to queue a command now. Note that there is an implicit
* assumption that every host can always queue at least one command.
* If a host is inactive and cannot queue any commands, I don't see
* how things could possibly work anyways.
*/
if (cmd->device->device_blocked == 0) {
if (scsi_retry_command(cmd) == 0) {
return 0;
}
}
cmd->device->device_blocked = TRUE;
}
/*
* Register the fact that we own the thing for now.
*/
cmd->state = SCSI_STATE_MLQUEUE;
cmd->owner = SCSI_OWNER_MIDLEVEL;
cmd->bh_next = NULL;
/*
* Decrement the counters, since these commands are no longer
* active on the host/device.
*/
cmd->host->host_busy--;
cmd->device->device_busy--;
/*
* Insert this command at the head of the queue for it's device.
* It will go before all other commands that are already in the queue.
*/
scsi_insert_special_cmd(cmd, 1);
return 0;
}
|
