32V/usr/src/slowsys/sys/slp.c
#include "../h/param.h"
#include "../h/systm.h"
#include "../h/dir.h"
#include "../h/user.h"
#include "../h/proc.h"
#include "../h/text.h"
#include "../h/uba.h"
#include "../h/map.h"
#include "../h/file.h"
#include "../h/inode.h"
#include "../h/buf.h"
/*
* Give up the processor till a wakeup occurs
* on chan, at which time the process
* enters the scheduling queue at priority pri.
* The most important effect of pri is that when
* pri<=PZERO a signal cannot disturb the sleep;
* if pri>PZERO signals will be processed.
* Callers of this routine must be prepared for
* premature return, and check that the reason for
* sleeping has gone away.
*/
sleep(chan, pri)
caddr_t chan;
{
register struct proc *rp;
register s;
rp = u.u_procp;
s = spl6();
rp->p_stat = SSLEEP;
rp->p_wchan = chan;
rp->p_pri = pri;
if(pri > PZERO) {
if(issig()) {
rp->p_wchan = 0;
rp->p_stat = SRUN;
spl0();
goto psig;
}
spl0();
if(runin != 0) {
runin = 0;
wakeup((caddr_t)&runin);
}
swtch();
if(issig())
goto psig;
} else {
spl0();
swtch();
}
splx(s);
return;
/*
* If priority was low (>PZERO) and
* there has been a signal,
* execute non-local goto to
* the qsav location.
* (see trap1/trap.c)
*/
psig:
resume(u.u_procp->p_addr, u.u_qsav);
}
/*
* Wake up all processes sleeping on chan.
*/
wakeup(chan)
register caddr_t chan;
{
register struct proc *p;
register i;
int s;
p = &proc[0];
i = NPROC;
do {
if(p->p_wchan==chan && p->p_stat!=SZOMB) {
/*
* this code looks dumb, but
* there is a possible race due
* to interrupts.
*/
s = spl6();
if(p->p_wchan == chan)
setrun(p);
splx(s);
}
p++;
} while(--i);
}
/*
* when you are sure that it
* is impossible to get the
* 'proc on q' diagnostic, the
* diagnostic loop can be removed.
*/
setrq(p)
struct proc *p;
{
register struct proc *q;
register s;
s = spl6();
for(q=runq; q!=NULL; q=q->p_link)
if(q == p) {
printf("proc on q\n");
goto out;
}
p->p_link = runq;
runq = p;
out:
splx(s);
}
/*
* Set the process running;
* arrange for it to be swapped in if necessary.
*/
setrun(p)
register struct proc *p;
{
if (p->p_stat==0 || p->p_stat==SZOMB)
panic("Running a dead proc");
p->p_wchan = 0;
p->p_stat = SRUN;
setrq(p);
if(p->p_pri < curpri)
runrun++;
if(runout != 0 && (p->p_flag&SLOAD) == 0) {
runout = 0;
wakeup((caddr_t)&runout);
}
}
/*
* Set user priority.
* The rescheduling flag (runrun)
* is set if the priority is better
* than the currently running process.
*/
setpri(pp)
register struct proc *pp;
{
register p;
p = (pp->p_cpu & 0377)/16;
p += PUSER + pp->p_nice - NZERO;
if(p > 127)
p = 127;
if(p < curpri)
runrun++;
pp->p_pri = p;
return(p);
}
/*
* The main loop of the scheduling (swapping)
* process.
* The basic idea is:
* see if anyone wants to be swapped in;
* swap out processes until there is room;
* swap him in;
* repeat.
* The runout flag is set whenever someone is swapped out.
* Sched sleeps on it awaiting work.
*
* Sched sleeps on runin whenever it cannot find enough
* core (by swapping out or otherwise) to fit the
* selected swapped process. It is awakened when the
* core situation changes and in any case once per second.
*/
sched()
{
register struct proc *rp, *p;
register outage, inage;
int maxsize;
/*
* find user to swap in;
* of users ready, select one out longest
*/
loop:
spl6();
outage = -20000;
for (rp = &proc[0]; rp < &proc[NPROC]; rp++)
if (rp->p_stat==SRUN && (rp->p_flag&SLOAD)==0 &&
rp->p_time - (rp->p_nice-NZERO)*8 > outage) {
p = rp;
outage = rp->p_time - (rp->p_nice-NZERO)*8;
}
/*
* If there is no one there, wait.
*/
if (outage == -20000) {
runout++;
sleep((caddr_t)&runout, PSWP);
goto loop;
}
spl0();
/*
* See if there is core for that process;
* if so, swap it in.
*/
if (swapin(p))
goto loop;
/*
* none found.
* look around for core.
* Select the largest of those sleeping
* at bad priority; if none, select the oldest.
*/
spl6();
p = NULL;
maxsize = -1;
inage = -1;
for (rp = &proc[0]; rp < &proc[NPROC]; rp++) {
if (rp->p_stat==SZOMB
|| (rp->p_flag&(SSYS|SLOCK|SULOCK|SLOAD))!=SLOAD)
continue;
if (rp->p_textp && rp->p_textp->x_flag&XLOCK)
continue;
if (rp->p_stat==SSLEEP&&rp->p_pri>=PZERO || rp->p_stat==SSTOP) {
if (maxsize < rp->p_size) {
p = rp;
maxsize = rp->p_size;
}
} else if (maxsize<0 && (rp->p_stat==SRUN||rp->p_stat==SSLEEP)) {
if (rp->p_time+rp->p_nice-NZERO > inage) {
p = rp;
inage = rp->p_time+rp->p_nice-NZERO;
}
}
}
spl0();
/*
* Swap found user out if sleeping at bad pri,
* or if he has spent at least 2 seconds in core and
* the swapped-out process has spent at least 3 seconds out.
* Otherwise wait a bit and try again.
*/
if (maxsize>=0 || (outage>=3 && inage>=2)) {
p->p_flag &= ~SLOAD;
xswap(p, 1, 0);
goto loop;
}
spl6();
runin++;
sleep((caddr_t)&runin, PSWP);
goto loop;
}
/*
* Swap a process in.
* Allocate data and possible text separately.
* It would be better to do largest first.
*/
swapin(p)
register struct proc *p;
{
register struct text *xp;
register int a;
int x;
if ((a = malloc(coremap, p->p_size)) == NULL)
return(0);
if (xp = p->p_textp) {
xlock(xp);
if (xp->x_ccount==0) {
if ((x = malloc(coremap, xp->x_size)) == NULL) {
xunlock(xp);
mfree(coremap, p->p_size, a);
return(0);
}
xp->x_caddr = x;
if ((xp->x_flag&XLOAD)==0)
swap(xp->x_daddr,x,xp->x_size,B_READ);
}
xp->x_ccount++;
xunlock(xp);
}
swap(p->p_addr, a, p->p_size, B_READ);
mfree(swapmap, ctod(p->p_size), p->p_addr);
p->p_addr = a;
p->p_flag |= SLOAD;
p->p_time = 0;
return(1);
}
/*
* put the current process on
* the Q of running processes and
* call the scheduler.
*/
qswtch()
{
setrq(u.u_procp);
swtch();
}
/*
* This routine is called to reschedule the CPU.
* if the calling process is not in RUN state,
* arrangements for it to restart must have
* been made elsewhere, usually by calling via sleep.
* There is a race here. A process may become
* ready after it has been examined.
* In this case, idle() will be called and
* will return in at most 1HZ time.
* i.e. its not worth putting an spl() in.
*/
swtch()
{
register n;
register struct proc *p, *q, *pp, *pq;
/*
* If not the idle process, resume the idle process.
*/
if (u.u_procp != &proc[0]) {
if (save(u.u_rsav)) {
sureg();
return;
}
resume(proc[0].p_addr, u.u_qsav);
}
/*
* The first save returns nonzero when proc 0 is resumed
* by another process (above); then the second is not done
* and the process-search loop is entered.
*
* The first save returns 0 when swtch is called in proc 0
* from sched(). The second save returns 0 immediately, so
* in this case too the process-search loop is entered.
* Thus when proc 0 is awakened by being made runnable, it will
* find itself and resume itself at rsav, and return to sched().
*/
if (save(u.u_qsav)==0 && save(u.u_rsav))
return;
loop:
spl6();
runrun = 0;
pp = NULL;
q = NULL;
n = 128;
/*
* Search for highest-priority runnable process
*/
for(p=runq; p!=NULL; p=p->p_link) {
if((p->p_stat==SRUN) && (p->p_flag&SLOAD)) {
if(p->p_pri < n) {
pp = p;
pq = q;
n = p->p_pri;
}
}
q = p;
}
/*
* If no process is runnable, idle.
*/
p = pp;
if(p == NULL) {
idle();
goto loop;
}
q = pq;
if(q == NULL)
runq = p->p_link;
else
q->p_link = p->p_link;
curpri = n;
spl0();
/*
* The rsav (ssav) contents are interpreted in the new address space
*/
n = p->p_flag&SSWAP;
p->p_flag &= ~SSWAP;
resume(p->p_addr, n? u.u_ssav: u.u_rsav);
}
/*
* Create a new process-- the internal version of
* sys fork.
* It returns 1 in the new process, 0 in the old.
*/
newproc()
{
int a1, a2;
struct proc *p, *up;
register struct proc *rpp, *rip;
register n;
p = NULL;
/*
* First, just locate a slot for a process
* and copy the useful info from this process into it.
* The panic "cannot happen" because fork has already
* checked for the existence of a slot.
*/
retry:
mpid++;
if(mpid >= 30000) {
mpid = 0;
goto retry;
}
for(rpp = &proc[0]; rpp < &proc[NPROC]; rpp++) {
if(rpp->p_stat == NULL && p==NULL)
p = rpp;
if (rpp->p_pid==mpid || rpp->p_pgrp==mpid)
goto retry;
}
if ((rpp = p)==NULL)
panic("no procs");
/*
* make proc entry for new proc
*/
rip = u.u_procp;
up = rip;
rpp->p_stat = SRUN;
rpp->p_clktim = 0;
rpp->p_flag = SLOAD;
rpp->p_uid = rip->p_uid;
rpp->p_pgrp = rip->p_pgrp;
rpp->p_nice = rip->p_nice;
rpp->p_textp = rip->p_textp;
rpp->p_pid = mpid;
rpp->p_ppid = rip->p_pid;
rpp->p_time = 0;
rpp->p_cpu = 0;
/*
* make duplicate entries
* where needed
*/
for(n=0; n<NOFILE; n++)
if(u.u_ofile[n] != NULL)
u.u_ofile[n]->f_count++;
if(up->p_textp != NULL) {
up->p_textp->x_count++;
up->p_textp->x_ccount++;
}
u.u_cdir->i_count++;
if (u.u_rdir)
u.u_rdir->i_count++;
/*
* Partially simulate the environment
* of the new process so that when it is actually
* created (by copying) it will look right.
*/
rpp = p;
u.u_procp = rpp;
rip = up;
n = rip->p_size;
a1 = rip->p_addr;
rpp->p_size = n;
/*
* When the resume is executed for the new process,
* here's where it will resume.
*/
if (save(u.u_ssav)) {
sureg();
return(1);
}
a2 = malloc(coremap, n);
/*
* If there is not enough core for the
* new process, swap out the current process to generate the
* copy.
*/
if(a2 == NULL) {
rip->p_stat = SIDL;
rpp->p_addr = a1;
xswap(rpp, 0, 0);
rip->p_stat = SRUN;
} else {
/*
* There is core, so just copy.
*/
rpp->p_addr = a2;
while(n--)
copyseg(a1++, a2++);
}
u.u_procp = rip;
setrq(rpp);
rpp->p_flag |= SSWAP;
return(0);
}
/*
* Change the size of the data+stack regions of the process.
* If the size is shrinking, it's easy-- just release the extra core.
* If it's growing, and there is core, just allocate it
* and copy the image, taking care to reset registers to account
* for the fact that the system's stack has moved.
* If there is no core, arrange for the process to be swapped
* out after adjusting the size requirement-- when it comes
* in, enough core will be allocated.
*
* After the expansion, the caller will take care of copying
* the user's stack towards or away from the data area.
*/
expand(newsize)
{
register i, n;
register struct proc *p;
register a1, a2;
p = u.u_procp;
n = p->p_size;
p->p_size = newsize;
a1 = p->p_addr;
if(n >= newsize) {
mfree(coremap, n-newsize, a1+newsize);
return;
}
if (save(u.u_ssav)) {
sureg();
return;
}
a2 = malloc(coremap, newsize);
if(a2 == NULL) {
xswap(p, 1, n);
p->p_flag |= SSWAP;
qswtch();
/* no return */
}
p->p_addr = a2;
for(i=0; i<n; i++)
copyseg(a1+i, a2+i);
mfree(coremap, n, a1);
resume(a2, u.u_ssav);
}