diff options
Diffstat (limited to 'io.c')
| -rw-r--r-- | io.c | 65 |
1 files changed, 43 insertions, 22 deletions
@@ -9,14 +9,13 @@ #include <stdio.h>
#include "mpx.h"
-#define DS_OFFSET 6 // was 3 before
+#define DS_OFFSET 6
-int count = 0;
void IO_sup(pcb *p) {
- char far *buffer;
- int far *length;
- unsigned *ds_add;
- int con_w = 0;
+ char far *buffer; // far pointer to the io buffer
+ int far *length; // far pointer to an int representing length of the io buffer
+ unsigned *ds_add; // data segment address
+ int con_w = 0; // flag for if the request was a con_write request
int rc;
disable();
@@ -69,6 +68,9 @@ void IO_sup(pcb *p) { // put the pcb back in the ready queue, if it was a con_write
if (con_w == 1) {
insert_pcb(&ready_queue_locked, p,0);
+ p->state = READY;
+ } else {
+ p->state = BLOCKED;
}
enable();
return;
@@ -81,9 +83,14 @@ int IO_complete(int device, int *stk_ptr) { dcb *d;
disable();
+ // get the dcb for the requested device
switch (device){
case CON:
d = &con;
+ // the con dcb isn't managed by con drive
+ // so we need to reset it here, but the
+ // other dcbs are handled in those files
+ // before calling io_complete
d->current_op = NO_OP;
break;
case COM:
@@ -111,20 +118,32 @@ int IO_complete(int device, int *stk_ptr) { // insert into ready queue
insert_pcb(&ready_queue_locked, current, 0);
- // set its state to ready
- current->state = READY;
+ // set its state to ready, unless it became
+ // a zombie while it was waiting for io to complete
+ if (current->state != ZOMBIE) {
+ current->state = READY;
+ }
- if (strcmp(d->current_pcb->name, "iocom2")==0) {
- count++;
- if (count > 20) {
- d = &com;
+ if (io_init_queue_locked != NULL) {
+ // if there are pending IO requests schedule them
+ current = io_init_queue_locked;
+ while (current != NULL && current->parm_add->op_number != device) {
+ current = current->next;
+ }
+
+ if (current != NULL) {
+ // take the pcb out of the io_init queue
+ remove_pcb(&io_init_queue_locked, current);
+
+ // if it wasn't terminated while waiting for io...
+ if (current->state != ZOMBIE) {
+ // ... schedule the io
+ IO_sched(current);
+ } else {
+ // send the zombie back to be ... dispatched ... muahaha
+ insert_pcb(&ready_queue_locked, current, 0);
+ }
}
- }
- if (d->pcb_head != NULL) {
- // if there are pending IO requests for this device
- //schedule them (IO_sched)
- remove_pcb(&(d->pcb_head), d->pcb_head);
- IO_sched(d->pcb_head);
}
outportb(0x20,0x20); // EOI signal
@@ -145,6 +164,7 @@ int IO_sched(pcb *p) { int op_num;
int op_type;
+ disable();
if (DEBUG_PRINTS) {printf("in io sched\n");}
// determine which device is requested
@@ -176,17 +196,18 @@ int IO_sched(pcb *p) { return -2;
}
+ // If the device is busy
if (d->current_op != NO_OP) {
disable();
// put pcb in IO queue
- insert_pcb(&(d->pcb_head), p, 1);
- // take pcb out of ready q
- remove_pcb(&ready_queue_locked, p);
+ insert_pcb(&io_init_queue_locked, p, 1);
+ p->state = BLOCKED;
enable();
} else {
+ // If the device wasn't busy, start the io
d->current_pcb = p;
IO_sup(p);
}
-
+ enable();
return 0;
}
|