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no more proc[] entry per cpu for idle loop

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each cpu[] has its own gdt and tss
no per-proc gdt or tss, re-write cpu's in scheduler (you win, cliff)
main0() switches to cpu[0].mpstack
This commit is contained in:
rtm 2006-08-15 22:18:20 +00:00
parent 69332d1918
commit 350e63f7a9
8 changed files with 455 additions and 615 deletions
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10
Makefile
View file

@ -67,6 +67,10 @@ usertests : usertests.o $(ULIB)
$(LD) -N -e main -Ttext 0 -o usertests usertests.o $(ULIB) $(LD) -N -e main -Ttext 0 -o usertests usertests.o $(ULIB)
$(OBJDUMP) -S usertests > usertests.asm $(OBJDUMP) -S usertests > usertests.asm
fstests : fstests.o $(ULIB)
$(LD) -N -e main -Ttext 0 -o fstests fstests.o $(ULIB)
$(OBJDUMP) -S fstests > fstests.asm
echo : echo.o $(ULIB) echo : echo.o $(ULIB)
$(LD) -N -e main -Ttext 0 -o echo echo.o $(ULIB) $(LD) -N -e main -Ttext 0 -o echo echo.o $(ULIB)
$(OBJDUMP) -S echo > echo.asm $(OBJDUMP) -S echo > echo.asm
@ -102,12 +106,12 @@ rm : rm.o $(ULIB)
mkfs : mkfs.c fs.h mkfs : mkfs.c fs.h
cc -o mkfs mkfs.c cc -o mkfs mkfs.c
fs.img : mkfs userfs usertests echo cat readme init sh ls mkdir rm fs.img : mkfs userfs usertests echo cat readme init sh ls mkdir rm fstests
./mkfs fs.img userfs usertests echo cat readme init sh ls mkdir rm ./mkfs fs.img userfs usertests echo cat readme init sh ls mkdir rm fstests
-include *.d -include *.d
clean : clean :
rm -f *.o *.d *.asm vectors.S parport.out \ rm -f *.o *.d *.asm vectors.S parport.out \
bootblock kernel xv6.img user1 userfs usertests \ bootblock kernel xv6.img user1 userfs usertests \
fs.img mkfs echo init fs.img mkfs echo init fstests

283
Notes
View file

@ -22,32 +22,14 @@ no kernel malloc(), just kalloc() for user core
user pointers aren't valid in the kernel user pointers aren't valid in the kernel
setting up first process are interrupts turned on in the kernel? yes.
we do want a process zero, as template
but not runnable
just set up return-from-trap frame on new kernel stack
fake user program that calls exec
map text read-only?
shared text?
what's on the stack during a trap or sys call?
PUSHA before scheduler switch? for callee-saved registers.
segment contents?
what does iret need to get out of the kernel?
how does INT know what kernel stack to use?
are interrupts turned on in the kernel? probably.
per-cpu curproc
one tss per process, or one per cpu?
one segment array per cpu, or per process?
pass curproc explicitly, or implicit from cpu #? pass curproc explicitly, or implicit from cpu #?
e.g. argument to newproc()? e.g. argument to newproc()?
hmm, you need a global curproc[cpu] for trap() &c hmm, you need a global curproc[cpu] for trap() &c
test stack expansion no stack expansion
test running out of memory, process slots test running out of memory, process slots
we can't really use a separate stack segment, since stack addresses we can't really use a separate stack segment, since stack addresses
@ -56,16 +38,6 @@ data vs text. how can we have a gap between data and stack, so that
both can grow, without committing 4GB of physical memory? does this both can grow, without committing 4GB of physical memory? does this
mean we need paging? mean we need paging?
what's the simplest way to add the paging we need?
one page table, re-write it each time we leave the kernel?
page table per process?
probably need to use 0-0xffffffff segments, so that
both data and stack pointers always work
so is it now worth it to make a process's phys mem contiguous?
or could use segment limits and 4 meg pages?
but limits would prevent using stack pointers as data pointers
how to write-protect text? not important?
perhaps have fixed-size stack, put it in the data segment? perhaps have fixed-size stack, put it in the data segment?
oops, if kernel stack is in contiguous user phys mem, then moving oops, if kernel stack is in contiguous user phys mem, then moving
@ -87,19 +59,6 @@ test children being inherited by grandparent &c
some sleep()s should be interruptible by kill() some sleep()s should be interruptible by kill()
cli/sti in acquire/release should nest!
in case you acquire two locks
what would need fixing if we got rid of kernel_lock?
console output
proc_exit() needs lock on proc *array* to deallocate
kill() needs lock on proc *array*
allocator's free list
global fd table (really free-ness)
sys_close() on fd table
fork on proc list, also next pid
hold lock until public slots in proc struct initialized
locks locks
init_lock init_lock
sequences CPU startup sequences CPU startup
@ -110,37 +69,17 @@ locks
memory allocator memory allocator
printf printf
wakeup needs proc_table_lock
so we need recursive locks?
or you must hold the lock to call wakeup?
in general, the table locks protect both free-ness and in general, the table locks protect both free-ness and
public variables of table elements public variables of table elements
in many cases you can use table elements w/o a lock in many cases you can use table elements w/o a lock
e.g. if you are the process, or you are using an fd e.g. if you are the process, or you are using an fd
lock code shouldn't call cprintf...
nasty hack to allow locks before first process,
and to allow them in interrupts when curproc may be zero
race between release and sleep in sys_wait()
race between sys_exit waking up parent and setting state=ZOMBIE
race in pipe code when full/empty
lock order lock order
per-pipe lock per-pipe lock
proc_table_lock fd_table_lock kalloc_lock proc_table_lock fd_table_lock kalloc_lock
console_lock console_lock
condition variable + mutex that protects it do you have to be holding the mutex in order to call wakeup()? yes
proc * (for wait()), proc_table_lock
pipe structure, pipe lock
systematic way to test sleep races?
print something at the start of sleep?
do you have to be holding the mutex in order to call wakeup()?
device interrupts don't clear FL_IF device interrupts don't clear FL_IF
so a recursive timer interrupt is possible so a recursive timer interrupt is possible
@ -156,202 +95,11 @@ inode->count counts in-memory pointers to the struct
blocks and inodes have ad-hoc sleep-locks blocks and inodes have ad-hoc sleep-locks
provide a single mechanism? provide a single mechanism?
need to lock bufs in bio between bread and brelse
test 14-character file names test 14-character file names
and file arguments longer than 14 and file arguments longer than 14
and directories longer than one sector
kalloc() can return 0; do callers handle this right? kalloc() can return 0; do callers handle this right?
why directing interrupts to cpu 1 causes trouble
cpu 1 turns on interrupts with no tss!
and perhaps a stale gdt (from boot)
since it has never run a process, never called setupsegs()
but does cpu really need the tss?
not switching stacks
fake process per cpu, just for tss?
seems like a waste
move tss to cpu[]?
but tss points to per-process kernel stack
would also give us a gdt
OOPS that wasn't the problem
wait for other cpu to finish starting before enabling interrupts?
some kind of crash in ide_init ioapic_enable cprintf
move ide_init before mp_start?
didn't do any good
maybe cpu0 taking ide interrupt, cpu1 getting a nested lock error
cprintfs are screwed up if locking is off
often loops forever
hah, just use lpt alone
looks like cpu0 took the ide interrupt and was the last to hold
the lock, but cpu1 thinks it is nested
cpu0 is in load_icode / printf / cons_putc
probably b/c cpu1 cleared use_console_lock
cpu1 is in scheduler() / printf / acquire
1: init timer
0: init timer
cpu 1 initial nlock 1
ne0s:t iidd el_occnkt rc
onsole cpu 1 old caller stack 1001A5 10071D 104DFF 1049FE
panic: acquire
^CNext at t=33002418
(0) [0x00100091] 0008:0x00100091 (unk. ctxt): jmp .+0xfffffffe ; ebfe
(1) [0x00100332] 0008:0x00100332 (unk. ctxt): jmp .+0xfffffffe
why is output interleaved even before panic?
does release turn on interrupts even inside an interrupt handler?
overflowing cpu[] stack?
probably not, change from 512 to 4096 didn't do anything
1: init timer
0: init timer
cnpeus te11 linnitki aclo nnoolleek cp1u
ss oarltd sccahleldeul esrt aocnk cpu 0111 Ej6 buf1 01A3140 C5118
0
la anic1::7 0a0c0 uuirr e
^CNext at t=31691050
(0) [0x00100373] 0008:0x00100373 (unk. ctxt): jmp .+0xfffffffe ; ebfe
(1) [0x00100091] 0008:0x00100091 (unk. ctxt): jmp .+0xfffffffe ; ebfe
cpu0:
0: init timer
nested lock console cpu 0 old caller stack 1001e6 101a34 1 0
(that's mpmain)
panic: acquire
cpu1:
1: init timer
cpu 1 initial nlock 1
start scheduler on cpu 1 jmpbuf ...
la 107000 lr ...
that is, nlock != 0
maybe a race; acquire does
locked = 1
cpu = cpu()
what if another acquire calls holding w/ locked = 1 but
before cpu is set?
if I type a lot (kbd), i get a panic
cpu1 in scheduler: panic "holding locks in scheduler"
cpu0 also in the same panic!
recursive interrupt?
FL_IF is probably set during interrupt... is that correct?
again:
olding locks in scheduler
trap v 33 eip 100ED3 c (that is, interrupt while holding a lock)
100ed3 is in lapic_write
again:
trap v 33 eip 102A3C cpu 1 nlock 1 (in acquire)
panic: interrupt while holding a lock
again:
trap v 33 eip 102A3C cpu 1 nlock 1
panic: interrupt while holding a lock
OR is it the cprintf("kbd overflow")?
no, get panic even w/o that cprintf
OR a release() at interrupt time turns interrupts back on?
of course i don't think they were off...
OK, fixing trap.c to make interrupts turn off FL_IF
that makes it take longer, but still panics
(maybe b/c release sets FL_IF)
shouldn't something (PIC?) prevent recursive interrupts of same IRQ?
or should FL_IF be clear during all interrupts?
maybe acquire should remember old FL_IF value, release should restore
if acquire did cli()
DUH the increment of nlock in acquire() happens before the cli!
so the panic is probably not a real problem
test nlock, cli(), then increment?
BUT now userfs doesn't do the final cat README
AND w/ cprintf("kbd overflow"), panic holding locks in scheduler
maybe also simulataneous panic("interrupt while holding a lock")
again (holding down x key):
kbd overflow
kbd oaaniicloowh
olding locks in scheduler
trap v 33 eip 100F5F c^CNext at t=32166285
(0) [0x0010033e] 0008:0010033e (unk. ctxt): jmp .+0xfffffffe (0x0010033e) ; ebfe
(1) [0x0010005c] 0008:0010005c (unk. ctxt): jmp .+0xfffffffe (0x0010005c) ; ebfe
cpu0 paniced due to holding locks in scheduler
cpu1 got panic("interrupt while holding a lock")
again in lapic_write.
while re-enabling an IRQ?
again:
cpu 0 panic("holding locks in scheduler")
but didn't trigger related panics earlier in scheduler or sched()
of course the panic is right after release() and thus sti()
so we may be seeing an interrupt that left locks held
cpu 1 unknown panic
why does it happen to both cpus at the same time?
again:
cpu 0 panic("holding locks in scheduler")
but trap() didn't see any held locks on return
cpu 1 no apparent panic
again:
cpu 0 panic: holding too many locks in scheduler
cpu 1 panic: kbd_intr returned while holding a lock
again:
cpu 0 panic: holding too man
la 10d70c lr 10027b
those don't seem to be locks...
only place non-constant lock is used is sleep()'s 2nd arg
maybe register not preserved across context switch?
it's in %esi...
sched() doesn't touch %esi
%esi is evidently callee-saved
something to do with interrupts? since ordinarily it works
cpu 1 panic: kbd_int returned while holding a lock
la 107340 lr 107300
console_lock and kbd_lock
maybe console_lock is often not released due to change
in use_console_lock (panic on other cpu)
again:
cpu 0: panic: h...
la 10D78C lr 102CA0
cpu 1: panic: acquire FL_IF (later than cpu 0)
but if sleep() were acquiring random locks, we'd see panics
in release, after sleep() returned.
actually when system is idle, maybe no-one sleeps at all.
just scheduler() and interrupts
questions:
does userfs use pipes? or fork?
no
does anything bad happen if process 1 exits? eg exit() in cat.c
looks ok
are there really no processes left?
lock_init() so we can have a magic number?
HMM maybe the variables at the end of struct cpu are being overwritten
nlocks, lastacquire, lastrelease
by cpu->stack?
adding junk buffers maybe causes crash to take longer...
when do we run on cpu stack?
just in scheduler()?
and interrupts from scheduler()
OH! recursive interrupts will use up any amount of cpu[].stack! OH! recursive interrupts will use up any amount of cpu[].stack!
underflow and wrecks *previous* cpu's struct underflow and wrecks *previous* cpu's struct
@ -360,15 +108,26 @@ mkdir
sh arguments sh arguments
sh redirection sh redirection
indirect blocks indirect blocks
two bugs in unlink: don't just return if nlink > 0,
and search for name, not inum
is there a create/create race for same file name? is there a create/create race for same file name?
resulting in two entries w/ same name in directory? resulting in two entries w/ same name in directory?
why does shell often ignore first line of input?
test: one process unlinks a file while another links to it test: one process unlinks a file while another links to it
test: simultaneous create of same file
test: one process opens a file while another deletes it test: one process opens a file while another deletes it
test: mkdir. deadlock d/.. vs ../d
wdir should use writei, to avoid special-case block allocation make proc[0] runnable
also readi cpu early tss and gdt
is dir locked? probably how do we get cpu0 scheduler() to use mpstack, not proc[0].kstack?
when iget() first sleeps, where does it longjmp to?
maybe set up proc[0] to be runnable, with entry proc0main(), then
have main() call scheduler()?
perhaps so proc[0] uses right kstack?
and scheduler() uses mpstack?
ltr sets the busy bit in the TSS, faults if already set
so gdt and TSS per cpu?
we don't want to be using some random process's gdt when it changes it.
maybe get rid of per-proc gdt and ts
one per cpu
refresh it when needed
setupsegs(proc *)

380
fstests.c Normal file
View file

@ -0,0 +1,380 @@
#include "user.h"
#include "fcntl.h"
char buf[512];
// two processes write to the same file descriptor
// is the offset shared? does inode locking work?
void
sharedfd()
{
int fd, pid, i, n, nc, np;
char buf[10];
unlink("sharedfd");
fd = open("sharedfd", O_CREATE|O_RDWR);
if(fd < 0){
printf(1, "fstests: cannot open sharedfd for writing");
return;
}
pid = fork();
memset(buf, pid==0?'c':'p', sizeof(buf));
for(i = 0; i < 100; i++){
if(write(fd, buf, sizeof(buf)) != sizeof(buf)){
printf(1, "fstests: write sharedfd failed\n");
break;
}
}
if(pid == 0)
exit();
else
wait();
close(fd);
fd = open("sharedfd", 0);
if(fd < 0){
printf(1, "fstests: cannot open sharedfd for reading\n");
return;
}
nc = np = 0;
while((n = read(fd, buf, sizeof(buf))) > 0){
for(i = 0; i < sizeof(buf); i++){
if(buf[i] == 'c')
nc++;
if(buf[i] == 'p')
np++;
}
}
close(fd);
unlink("sharedfd");
if(nc == 1000 && np == 1000)
printf(1, "sharedfd ok\n");
else
printf(1, "sharedfd oops %d %d\n", nc, np);
}
// two processes write two different files at the same
// time, to test block allocation.
void
twofiles()
{
int fd, pid, i, j, n, total;
char *fname;
unlink("f1");
unlink("f2");
pid = fork();
if(pid < 0){
puts("fork failed\n");
return;
}
fname = pid ? "f1" : "f2";
fd = open(fname, O_CREATE | O_RDWR);
if(fd < 0){
puts("create failed\n");
exit();
}
memset(buf, pid?'p':'c', 512);
for(i = 0; i < 12; i++){
if((n = write(fd, buf, 500)) != 500){
printf(1, "write failed %d\n", n);
exit();
}
}
close(fd);
if(pid)
wait();
else
exit();
for(i = 0; i < 2; i++){
fd = open(i?"f1":"f2", 0);
total = 0;
while((n = read(fd, buf, sizeof(buf))) > 0){
for(j = 0; j < n; j++){
if(buf[j] != (i?'p':'c')){
puts("wrong char\n");
exit();
}
}
total += n;
}
close(fd);
if(total != 12*500){
printf(1, "wrong length %d\n", total);
exit();
}
}
unlink("f1");
unlink("f2");
puts("twofiles ok\n");
}
// two processes create and delete files in same directory
void
createdelete()
{
int pid, i, fd;
int n = 20;
char name[32];
pid = fork();
if(pid < 0){
puts("fork failed\n");
exit();
}
name[0] = pid ? 'p' : 'c';
name[2] = '\0';
for(i = 0; i < n; i++){
name[1] = '0' + i;
fd = open(name, O_CREATE | O_RDWR);
if(fd < 0){
puts("create failed\n");
exit();
}
close(fd);
if(i > 0 && (i % 2 ) == 0){
name[1] = '0' + (i / 2);
if(unlink(name) < 0){
puts("unlink failed\n");
exit();
}
}
}
if(pid)
wait();
else
exit();
for(i = 0; i < n; i++){
name[0] = 'p';
name[1] = '0' + i;
fd = open(name, 0);
if((i == 0 || i >= n/2) && fd < 0){
printf(1, "oops createdelete %s didn't exist\n", name);
} else if((i >= 1 && i < n/2) && fd >= 0){
printf(1, "oops createdelete %s did exist\n", name);
}
if(fd >= 0)
close(fd);
name[0] = 'c';
name[1] = '0' + i;
fd = open(name, 0);
if((i == 0 || i >= n/2) && fd < 0){
printf(1, "oops createdelete %s didn't exist\n", name);
} else if((i >= 1 && i < n/2) && fd >= 0){
printf(1, "oops createdelete %s did exist\n", name);
}
if(fd >= 0)
close(fd);
}
for(i = 0; i < n; i++){
name[0] = 'p';
name[1] = '0' + i;
unlink(name);
name[0] = 'c';
unlink(name);
}
printf(1, "createdelete ok\n");
}
// can I unlink a file and still read it?
void
unlinkread()
{
int fd, fd1;
fd = open("unlinkread", O_CREATE | O_RDWR);
if(fd < 0){
puts("create unlinkread failed\n");
exit();
}
write(fd, "hello", 5);
close(fd);
fd = open("unlinkread", O_RDWR);
if(fd < 0){
puts("open unlinkread failed\n");
exit();
}
if(unlink("unlinkread") != 0){
puts("unlink unlinkread failed\n");
exit();
}
fd1 = open("xxx", O_CREATE | O_RDWR);
write(fd1, "yyy", 3);
close(fd1);
if(read(fd, buf, sizeof(buf)) != 5){
puts("unlinkread read failed");
exit();
}
if(buf[0] != 'h'){
puts("unlinkread wrong data\n");
exit();
}
if(write(fd, buf, 10) != 10){
puts("unlinkread write failed\n");
exit();
}
close(fd);
unlink("xxx");
puts("unlinkread ok\n");
}
void
linktest()
{
int fd;
unlink("lf1");
unlink("lf2");
fd = open("lf1", O_CREATE|O_RDWR);
if(fd < 0){
puts("create lf1 failed\n");
exit();
}
if(write(fd, "hello", 5) != 5){
puts("write lf1 failed\n");
exit();
}
close(fd);
if(link("lf1", "lf2") < 0){
puts("link lf1 lf2 failed\n");
exit();
}
unlink("lf1");
if(open("lf1", 0) >= 0){
puts("unlinked lf1 but it is still there!\n");
exit();
}
fd = open("lf2", 0);
if(fd < 0){
puts("open lf2 failed\n");
exit();
}
if(read(fd, buf, sizeof(buf)) != 5){
puts("read lf2 failed\n");
exit();
}
close(fd);
if(link("lf2", "lf2") >= 0){
puts("link lf2 lf2 succeeded! oops\n");
exit();
}
unlink("lf2");
if(link("lf2", "lf1") >= 0){
puts("link non-existant succeeded! oops\n");
exit();
}
if(link(".", "lf1") >= 0){
puts("link . lf1 succeeded! oops\n");
exit();
}
puts("linktest ok\n");
}
// test concurrent create of the same file
void
concreate()
{
char file[3];
int i, pid, n, fd;
char fa[40];
struct {
unsigned short inum;
char name[14];
} de;
file[0] = 'C';
file[2] = '\0';
for(i = 0; i < 40; i++){
file[1] = '0' + i;
unlink(file);
pid = fork();
if(pid && (i % 3) == 1){
link("C0", file);
} else if(pid == 0 && (i % 5) == 1){
link("C0", file);
} else {
fd = open(file, O_CREATE | O_RDWR);
if(fd < 0){
puts("concreate create failed\n");
exit();
}
close(fd);
}
if(pid == 0)
exit();
else
wait();
}
memset(fa, 0, sizeof(fa));
fd = open(".", 0);
n = 0;
while(read(fd, &de, sizeof(de)) > 0){
if(de.inum == 0)
continue;
if(de.name[0] == 'C' && de.name[2] == '\0'){
i = de.name[1] - '0';
if(i < 0 || i >= sizeof(fa)){
printf(1, "concreate weird file %s\n", de.name);
exit();
}
if(fa[i]){
printf(1, "concreate duplicate file %s\n", de.name);
exit();
}
fa[i] = 1;
n++;
}
}
close(fd);
if(n != 40){
puts("concreate not enough files in directory listing\n");
exit();
}
for(i = 0; i < 40; i++){
file[1] = '0' + i;
unlink(file);
}
puts("concreate ok\n");
}
int
main(int argc, char *argv[])
{
puts("fstests starting\n");
concreate();
linktest();
unlinkread();
createdelete();
twofiles();
sharedfd();
puts("fstests finished\n");
exit();
}

23
main.c
View file

@ -29,10 +29,14 @@ main0(void)
// clear BSS // clear BSS
memset(edata, 0, end - edata); memset(edata, 0, end - edata);
// switch to cpu0's cpu stack
asm volatile("movl %0, %%esp" : : "r" (cpus[0].mpstack + MPSTACK - 32));
asm volatile("movl %0, %%ebp" : : "r" (cpus[0].mpstack + MPSTACK));
// Make sure interrupts stay disabled on all processors // Make sure interrupts stay disabled on all processors
// until each signals it is ready, by pretending to hold // until each signals it is ready, by pretending to hold
// an extra lock. // an extra lock.
// xxx maybe replace w/ acquire remembering if FL_IF // xxx maybe replace w/ acquire remembering if FL_IF was already clear
for(i=0; i<NCPU; i++){ for(i=0; i<NCPU; i++){
cpus[i].nlock++; cpus[i].nlock++;
cpus[i].guard1 = 0xdeadbeef; cpus[i].guard1 = 0xdeadbeef;
@ -55,16 +59,9 @@ main0(void)
fd_init(); fd_init();
iinit(); iinit();
// create a fake process per CPU
// so each CPU always has a tss and a gdt
for(p = &proc[0]; p < &proc[NCPU]; p++){
p->state = IDLEPROC;
p->kstack = cpus[p-proc].mpstack;
p->pid = p - proc;
}
// fix process 0 so that copyproc() will work // fix process 0 so that copyproc() will work
p = &proc[0]; p = &proc[0];
p->state = IDLEPROC;
p->sz = 4 * PAGE; p->sz = 4 * PAGE;
p->mem = kalloc(p->sz); p->mem = kalloc(p->sz);
memset(p->mem, 0, p->sz); memset(p->mem, 0, p->sz);
@ -74,8 +71,9 @@ main0(void)
p->tf->es = p->tf->ds = p->tf->ss = (SEG_UDATA << 3) | 3; p->tf->es = p->tf->ds = p->tf->ss = (SEG_UDATA << 3) | 3;
p->tf->cs = (SEG_UCODE << 3) | 3; p->tf->cs = (SEG_UCODE << 3) | 3;
p->tf->eflags = FL_IF; p->tf->eflags = FL_IF;
setupsegs(p);
// curproc[cpu()] = p; // make sure there's a TSS
setupsegs(0);
// initialize I/O devices, let them enable interrupts // initialize I/O devices, let them enable interrupts
console_init(); console_init();
@ -117,7 +115,8 @@ mpmain(void)
lapic_timerinit(); lapic_timerinit();
lapic_enableintr(); lapic_enableintr();
setupsegs(&proc[cpu()]); // make sure there's a TSS
setupsegs(0);
cpuid(0, 0, 0, 0, 0); // memory barrier cpuid(0, 0, 0, 0, 0); // memory barrier
cpus[cpu()].booted = 1; cpus[cpu()].booted = 1;

69
proc.c
View file

@ -11,7 +11,7 @@ struct spinlock proc_table_lock;
struct proc proc[NPROC]; struct proc proc[NPROC];
struct proc *curproc[NCPU]; struct proc *curproc[NCPU];
int next_pid = NCPU; int next_pid = 1;
extern void forkret(void); extern void forkret(void);
extern void forkret1(struct trapframe*); extern void forkret1(struct trapframe*);
@ -22,28 +22,39 @@ pinit(void)
} }
/* /*
* set up a process's task state and segment descriptors * set up CPU's segment descriptors and task state for a
* correctly, given its current size and address in memory. * given process. If p==0, set up for "idle" state for
* this should be called whenever the latter change. * when scheduler() isn't running any process.
* doesn't change the cpu's current segmentation setup.
*/ */
void void
setupsegs(struct proc *p) setupsegs(struct proc *p)
{ {
memset(&p->ts, 0, sizeof(struct taskstate)); struct cpu *c = &cpus[cpu()];
p->ts.ss0 = SEG_KDATA << 3;
p->ts.esp0 = (uint)(p->kstack + KSTACKSIZE); c->ts.ss0 = SEG_KDATA << 3;
if(p){
c->ts.esp0 = (uint)(p->kstack + KSTACKSIZE);
} else {
c->ts.esp0 = 0xffffffff;
}
// XXX it may be wrong to modify the current segment table! // XXX it may be wrong to modify the current segment table!
p->gdt[0] = SEG_NULL; c->gdt[0] = SEG_NULL;
p->gdt[SEG_KCODE] = SEG(STA_X|STA_R, 0, 0x100000 + 64*1024, 0); // xxx c->gdt[SEG_KCODE] = SEG(STA_X|STA_R, 0, 0x100000 + 64*1024, 0); // xxx
p->gdt[SEG_KDATA] = SEG(STA_W, 0, 0xffffffff, 0); c->gdt[SEG_KDATA] = SEG(STA_W, 0, 0xffffffff, 0);
p->gdt[SEG_TSS] = SEG16(STS_T32A, (uint) &p->ts, c->gdt[SEG_TSS] = SEG16(STS_T32A, (uint) &c->ts, sizeof(c->ts), 0);
sizeof(p->ts), 0); c->gdt[SEG_TSS].s = 0;
p->gdt[SEG_TSS].s = 0; if(p){
p->gdt[SEG_UCODE] = SEG(STA_X|STA_R, (uint)p->mem, p->sz, 3); c->gdt[SEG_UCODE] = SEG(STA_X|STA_R, (uint)p->mem, p->sz, 3);
p->gdt[SEG_UDATA] = SEG(STA_W, (uint)p->mem, p->sz, 3); c->gdt[SEG_UDATA] = SEG(STA_W, (uint)p->mem, p->sz, 3);
} else {
c->gdt[SEG_UCODE] = SEG_NULL;
c->gdt[SEG_UDATA] = SEG_NULL;
}
lgdt(c->gdt, sizeof c->gdt);
ltr(SEG_TSS << 3);
} }
// Look in the process table for an UNUSED proc. // Look in the process table for an UNUSED proc.
@ -101,9 +112,6 @@ copyproc(struct proc* p)
np->state = UNUSED; np->state = UNUSED;
return 0; return 0;
} }
// Initialize segment table.
setupsegs(np);
// Copy trapframe registers from parent. // Copy trapframe registers from parent.
np->tf = (struct trapframe*)(np->kstack + KSTACKSIZE) - 1; np->tf = (struct trapframe*)(np->kstack + KSTACKSIZE) - 1;
@ -159,26 +167,11 @@ scheduler(void)
if(p->state != RUNNABLE) if(p->state != RUNNABLE)
continue; continue;
// Run this process.
// XXX move this into swtch or trapret or something.
// It can run on the other stack.
// h/w sets busy bit in TSS descriptor sometimes, and faults
// if it's set in LTR. so clear tss descriptor busy bit.
p->gdt[SEG_TSS].type = STS_T32A;
// XXX should probably have an lgdt() function in x86.h
// to confine all the inline assembly.
// XXX probably ought to lgdt on trap return too, in case
// a system call has moved a program or changed its size.
lgdt(p->gdt, sizeof p->gdt);
// asm volatile("lgdt %0" : : "g" (p->gdt_pd.lim));
ltr(SEG_TSS << 3);
// Switch to chosen process. It is the process's job // Switch to chosen process. It is the process's job
// to release proc_table_lock and then reacquire it // to release proc_table_lock and then reacquire it
// before jumping back to us. // before jumping back to us.
if(0) cprintf("cpu%d: run %d\n", cpu(), p-proc);
setupsegs(p);
curproc[cpu()] = p; curproc[cpu()] = p;
p->state = RUNNING; p->state = RUNNING;
if(setjmp(&cpus[cpu()].jmpbuf) == 0) if(setjmp(&cpus[cpu()].jmpbuf) == 0)
@ -199,9 +192,7 @@ scheduler(void)
panic("scheduler lock"); panic("scheduler lock");
} }
setupsegs(&proc[cpu()]); setupsegs(0);
// XXX if not holding proc_table_lock panic.
} }
release(&proc_table_lock); release(&proc_table_lock);

4
proc.h
View file

@ -48,8 +48,6 @@ struct proc{
struct fd *fds[NOFILE]; struct fd *fds[NOFILE];
struct inode *cwd; struct inode *cwd;
struct taskstate ts; // only to give cpu address of kernel stack
struct segdesc gdt[NSEGS];
uint esp; // kernel stack pointer uint esp; // kernel stack pointer
uint ebp; // kernel frame pointer uint ebp; // kernel frame pointer
@ -67,6 +65,8 @@ extern struct proc *curproc[NCPU]; // can be NULL if no proc running.
struct cpu { struct cpu {
uchar apicid; // Local APIC ID uchar apicid; // Local APIC ID
struct jmpbuf jmpbuf; struct jmpbuf jmpbuf;
struct taskstate ts; // only to give cpu address of kernel stack
struct segdesc gdt[NSEGS];
int guard1; int guard1;
char mpstack[MPSTACK]; // per-cpu start-up stack char mpstack[MPSTACK]; // per-cpu start-up stack
int guard2; int guard2;

7
trap.c
View file

@ -41,8 +41,8 @@ trap(struct trapframe *tf)
panic("interrupt while holding a lock"); panic("interrupt while holding a lock");
} }
if(cpu() == 1 && curproc[cpu()] == 0){ if(curproc[cpu()] == 0){
if(&tf < cpus[cpu()].mpstack || &tf > cpus[cpu()].mpstack + 512){ if(&tf < cpus[cpu()].mpstack || &tf > cpus[cpu()].mpstack + MPSTACK){
cprintf("&tf %x mpstack %x\n", &tf, cpus[cpu()].mpstack); cprintf("&tf %x mpstack %x\n", &tf, cpus[cpu()].mpstack);
panic("trap cpu stack"); panic("trap cpu stack");
} }
@ -125,7 +125,8 @@ trap(struct trapframe *tf)
return; return;
} }
cprintf("trap %d\n", v); cprintf("trap %d from cpu %d eip %x\n", v, cpu(), tf->eip);
panic("trap");
return; return;
} }

294
usertests.c
View file

@ -115,305 +115,11 @@ exitwait(void)
puts("exitwait ok\n"); puts("exitwait ok\n");
} }
// two processes write to the same file descriptor
// is the offset shared? does inode locking work?
void
sharedfd()
{
int fd, pid, i, n, nc, np;
char buf[10];
unlink("sharedfd");
fd = open("sharedfd", O_CREATE|O_RDWR);
if(fd < 0){
printf(1, "usertests: cannot open sharedfd for writing");
return;
}
pid = fork();
memset(buf, pid==0?'c':'p', sizeof(buf));
for(i = 0; i < 100; i++){
if(write(fd, buf, sizeof(buf)) != sizeof(buf)){
printf(1, "usertests: write sharedfd failed\n");
break;
}
}
if(pid == 0)
exit();
else
wait();
close(fd);
fd = open("sharedfd", 0);
if(fd < 0){
printf(1, "usertests: cannot open sharedfd for reading\n");
return;
}
nc = np = 0;
while((n = read(fd, buf, sizeof(buf))) > 0){
for(i = 0; i < sizeof(buf); i++){
if(buf[i] == 'c')
nc++;
if(buf[i] == 'p')
np++;
}
}
close(fd);
unlink("sharedfd");
if(nc == 1000 && np == 1000)
printf(1, "sharedfd ok\n");
else
printf(1, "sharedfd oops %d %d\n", nc, np);
}
// two processes write two different files at the same
// time, to test block allocation.
void
twofiles()
{
int fd, pid, i, j, n, total;
char *fname;
unlink("f1");
unlink("f2");
pid = fork();
if(pid < 0){
puts("fork failed\n");
return;
}
fname = pid ? "f1" : "f2";
fd = open(fname, O_CREATE | O_RDWR);
if(fd < 0){
puts("create failed\n");
exit();
}
memset(buf, pid?'p':'c', 512);
for(i = 0; i < 12; i++){
if((n = write(fd, buf, 500)) != 500){
printf(1, "write failed %d\n", n);
exit();
}
}
close(fd);
if(pid)
wait();
else
exit();
for(i = 0; i < 2; i++){
fd = open(i?"f1":"f2", 0);
total = 0;
while((n = read(fd, buf, sizeof(buf))) > 0){
for(j = 0; j < n; j++){
if(buf[j] != (i?'p':'c')){
puts("wrong char\n");
exit();
}
}
total += n;
}
close(fd);
if(total != 12*500){
printf(1, "wrong length %d\n", total);
exit();
}
}
unlink("f1");
unlink("f2");
puts("twofiles ok\n");
}
// two processes create and delete files in same directory
void
createdelete()
{
int pid, i, fd;
int n = 20;
char name[32];
pid = fork();
if(pid < 0){
puts("fork failed\n");
exit();
}
name[0] = pid ? 'p' : 'c';
name[2] = '\0';
for(i = 0; i < n; i++){
name[1] = '0' + i;
fd = open(name, O_CREATE | O_RDWR);
if(fd < 0){
puts("create failed\n");
exit();
}
close(fd);
if(i > 0 && (i % 2 ) == 0){
name[1] = '0' + (i / 2);
if(unlink(name) < 0){
puts("unlink failed\n");
exit();
}
}
}
if(pid)
wait();
else
exit();
for(i = 0; i < n; i++){
name[0] = 'p';
name[1] = '0' + i;
fd = open(name, 0);
if((i == 0 || i >= n/2) && fd < 0){
printf(1, "oops createdelete %s didn't exist\n", name);
} else if((i >= 1 && i < n/2) && fd >= 0){
printf(1, "oops createdelete %s did exist\n", name);
}
if(fd >= 0)
close(fd);
name[0] = 'c';
name[1] = '0' + i;
fd = open(name, 0);
if((i == 0 || i >= n/2) && fd < 0){
printf(1, "oops createdelete %s didn't exist\n", name);
} else if((i >= 1 && i < n/2) && fd >= 0){
printf(1, "oops createdelete %s did exist\n", name);
}
if(fd >= 0)
close(fd);
}
for(i = 0; i < n; i++){
name[0] = 'p';
name[1] = '0' + i;
unlink(name);
name[0] = 'c';
unlink(name);
}
printf(1, "createdelete ok\n");
}
// can I unlink a file and still read it?
void
unlinkread()
{
int fd, fd1;
fd = open("unlinkread", O_CREATE | O_RDWR);
if(fd < 0){
puts("create unlinkread failed\n");
exit();
}
write(fd, "hello", 5);
close(fd);
fd = open("unlinkread", O_RDWR);
if(fd < 0){
puts("open unlinkread failed\n");
exit();
}
if(unlink("unlinkread") != 0){
puts("unlink unlinkread failed\n");
exit();
}
fd1 = open("xxx", O_CREATE | O_RDWR);
write(fd1, "yyy", 3);
close(fd1);
if(read(fd, buf, sizeof(buf)) != 5){
puts("unlinkread read failed");
exit();
}
if(buf[0] != 'h'){
puts("unlinkread wrong data\n");
exit();
}
if(write(fd, buf, 10) != 10){
puts("unlinkread write failed\n");
exit();
}
close(fd);
unlink("xxx");
puts("unlinkread ok\n");
}
void
linktest()
{
int fd;
unlink("lf1");
unlink("lf2");
fd = open("lf1", O_CREATE|O_RDWR);
if(fd < 0){
puts("create lf1 failed\n");
exit();
}
if(write(fd, "hello", 5) != 5){
puts("write lf1 failed\n");
exit();
}
close(fd);
if(link("lf1", "lf2") < 0){
puts("link lf1 lf2 failed\n");
exit();
}
unlink("lf1");
if(open("lf1", 0) >= 0){
puts("unlinked lf1 but it is still there!\n");
exit();
}
fd = open("lf2", 0);
if(fd < 0){
puts("open lf2 failed\n");
exit();
}
if(read(fd, buf, sizeof(buf)) != 5){
puts("read lf2 failed\n");
exit();
}
close(fd);
if(link("lf2", "lf2") >= 0){
puts("link lf2 lf2 succeeded! oops\n");
exit();
}
unlink("lf2");
if(link("lf2", "lf1") >= 0){
puts("link non-existant succeeded! oops\n");
exit();
}
if(link(".", "lf1") >= 0){
puts("link . lf1 succeeded! oops\n");
exit();
}
puts("linktest ok\n");
}
int int
main(int argc, char *argv[]) main(int argc, char *argv[])
{ {
puts("usertests starting\n"); puts("usertests starting\n");
linktest();
unlinkread();
createdelete();
twofiles();
sharedfd();
pipe1(); pipe1();
preempt(); preempt();
exitwait(); exitwait();