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minix/kernel/proc.c
Jorrit Herder ac0995259d *** empty log message ***
2005-05-02 14:30:04 +00:00

565 lines
21 KiB
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/* This file contains essentially all of the process and message handling.
* It has two main entry points from the outside:
*
* sys_call: a system call, that is, the kernel is trapped with an INT
* notify: notify process of a system event (notifications aren't queued)
*
* It also has several minor entry points:
*
* lock_ready: put a process on one of the ready queues so it can be run
* lock_unready: remove a process from the ready queues
* lock_sched: a process has run too long; schedule another one
* lock_pick_proc: pick a process to run (used by system initialization)
* unhold: repeat all held-up notifications
*
* Changes:
* Nov 05, 2004 removed lock_mini_send() (Jorrit N. Herder)
* Oct 28, 2004 non-blocking SEND and RECEIVE (Jorrit N. Herder)
* Oct 28, 2004 rewrite of sys_call() (Jorrit N. Herder)
* Oct 10, 2004 require BOTH for kernel sys_call() (Jorrit N. Herder)
* (to protect kernel tasks from being blocked)
* Sep 25, 2004 generalized notify() function (Jorrit N. Herder)
* Sep 23, 2004 removed PM sig check in mini_rec() (Jorrit N. Herder)
* Aug 19, 2004 generalized ready()/unready() (Jorrit N. Herder)
* Aug 18, 2004 added notify() function (Jorrit N. Herder)
* May 01, 2004 check p_sendmask in mini_send() (Jorrit N. Herder)
*/
#include "kernel.h"
#include <minix/callnr.h>
#include <minix/com.h>
#include "proc.h"
#include "sendmask.h"
PRIVATE unsigned char switching; /* nonzero to inhibit notify() */
FORWARD _PROTOTYPE( int mini_send, (struct proc *caller_ptr, int dest,
message *m_ptr, int may_block) );
FORWARD _PROTOTYPE( int mini_rec, (struct proc *caller_ptr, int src,
message *m_ptr, int may_block) );
FORWARD _PROTOTYPE( void ready, (struct proc *rp) );
FORWARD _PROTOTYPE( void sched, (void) );
FORWARD _PROTOTYPE( void unready, (struct proc *rp) );
FORWARD _PROTOTYPE( void pick_proc, (void) );
#if (CHIP == M68000)
FORWARD _PROTOTYPE( void cp_mess, (int src, struct proc *src_p, message *src_m,
struct proc *dst_p, message *dst_m) );
#endif
#if (CHIP == INTEL)
#define CopyMess(s,sp,sm,dp,dm) \
cp_mess(s, (sp)->p_memmap[D].mem_phys, (vir_bytes)sm, (dp)->p_memmap[D].mem_phys, (vir_bytes)dm)
#endif /* (CHIP == INTEL) */
#if (CHIP == M68000)
/* M68000 does not have cp_mess() in assembly like INTEL. Declare prototype
* for cp_mess() here and define the function below. Also define CopyMess.
*/
#endif /* (CHIP == M68000) */
/* Bit mask operations used to bits of the notification mask. */
#define set_bit(mask, n) ((mask) |= (1 << (n)))
#define clear_bit(mask, n) ((mask) &= ~(1 << (n)))
#define isset_bit(mask, n) ((mask) & (1 << (n)))
/*===========================================================================*
* notify *
*===========================================================================*/
PUBLIC void notify(proc_nr, notify_type)
int proc_nr; /* number of process to be started */
int notify_type; /* notification to be sent */
{
/* A system event has occurred. Send a notification with source HARDWARE to
* the given process. The notify() function was carefully designed so that it
* (1) can be used safely from both interrupt handlers and the task level, and
* (2) realizes asynchronous message passing with at least once semantics,
* that is, the notifications are not queued. If a race condition occurs, the
* notification is queued and repeated later by unhold(). If the receiver is
* not ready, the notification is blocked and checked later in receive().
*/
register struct proc *rp; /* pointer to task's proc entry */
message m; /* message to send the notification */
unsigned int notify_bit; /* bit for this notification */
/* Get notify bit and process pointer. */
notify_bit = (unsigned int) (notify_type - NOTIFICATION);
rp = proc_addr(proc_nr);
/* If this call would compete with other process-switching functions, put
* it on the 'held' queue to be flushed at the next non-competing restart().
* The competing conditions are:
* (1) k_reenter == (typeof k_reenter) -1:
* Call from the task level, typically from an output interrupt
* routine. An interrupt handler might reenter notify(). Rare,
* so not worth special treatment.
* (2) k_reenter > 0:
* Call from a nested interrupt handler. A previous interrupt
* handler might be inside notify() or sys_call().
* (3) switching != 0:
* A process-switching function other than notify() is being called
* from the task level, typically sched() from CLOCK. An interrupt
* handler might call notify() and pass the 'k_reenter' test.
*/
if (k_reenter != 0 || switching) {
lock();
if (! rp->p_ntf_held) { /* already on held queue? */
if (held_head != NIL_PROC)
held_tail->p_ntf_nextheld = rp;
else
held_head = rp;
held_tail = rp;
rp->p_ntf_nextheld = NIL_PROC;
}
set_bit(rp->p_ntf_held, notify_bit); /* add bit to held mask */
unlock();
return;
}
switching = TRUE;
/* If process is not waiting for a notification, record the blockage. */
if ( (rp->p_flags & (RECEIVING | SENDING)) != RECEIVING ||
!isrxhardware(rp->p_getfrom)) {
set_bit(rp->p_ntf_blocked, notify_bit); /* add bit to blocked mask */
switching = FALSE;
return;
}
/* Destination is waiting for a notification. Send it a message with source
* HARDWARE and type 'notify_type'. No more information can be reliably
* provided since notifications are not queued.
*/
m.m_source = HARDWARE; /* direct copy does not work for servers */
m.m_type = notify_type;
CopyMess(HARDWARE, proc_addr(HARDWARE), &m, rp, rp->p_messbuf);
rp->p_flags &= ~RECEIVING;
clear_bit(rp->p_ntf_blocked, notify_bit);
/* Announce the process ready and select a fresh process to run. */
ready(rp);
pick_proc();
switching = FALSE;
}
/*===========================================================================*
* sys_call *
*===========================================================================*/
PUBLIC int sys_call(call_nr, src_dst, m_ptr)
int call_nr; /* (NB_)SEND, (NB_)RECEIVE, BOTH */
int src_dst; /* source to receive from or dest to send to */
message *m_ptr; /* pointer to message in the caller's space */
{
/* System calls are done by trapping to the kernel with an INT instruction.
* The trap is caught and sys_call() is called to send or receive a message
* (or both). The caller is always given by 'proc_ptr'.
*/
register struct proc *caller_ptr = proc_ptr; /* get pointer to caller */
int function = call_nr & SYSCALL_FUNC; /* get system call function */
int may_block = ! (call_nr & NON_BLOCKING); /* (dis)allow blocking? */
int mask_entry; /* bit to check in send mask */
int result; /* the system call's result */
/* Calls directed to the kernel may only be sendrec(), because tasks always
* reply and may not block if the caller doesn't do receive(). Users also
* may only use sendrec() to protect the process manager and file system.
*/
if ((iskernel(src_dst) || isuserp(caller_ptr)) && function != BOTH) {
result = ECALLDENIED; /* BOTH was required */
}
/* Verify that requested source and/ or destination is a valid process. */
else if (! isoksrc_dst(src_dst)) {
result = EBADSRCDST; /* invalid process number */
}
/* Now check if the call is known and try to perform the request. The only
* system calls that exist in MINIX are sending and receiving messages.
* Receiving is straightforward. Sending requires checks to see if sending
* is allowed by the caller's send mask and to see if the destination is
* alive.
*/
else {
switch(function) {
case SEND:
/* fall through, SEND is done in BOTH */
case BOTH:
if (! isalive(src_dst)) {
result = EDEADDST; /* cannot send to the dead */
break;
}
mask_entry = isuser(src_dst) ? USER_PROC_NR : src_dst;
if (! isallowed(caller_ptr->p_sendmask, mask_entry)) {
kprintf("WARNING: sys_call denied %d ", caller_ptr->p_nr);
kprintf("sending to %d\n", proc_addr(src_dst)->p_nr);
result = ECALLDENIED; /* call denied by send mask */
break;
}
result = mini_send(caller_ptr, src_dst, m_ptr, may_block);
if (function == SEND || result != OK) {
break; /* done, or SEND failed */
} /* fall through for BOTH */
case RECEIVE:
result = mini_rec(caller_ptr, src_dst, m_ptr, may_block);
break;
default:
result = EBADCALL; /* illegal system call */
}
}
/* Now, return the result of the system call to the caller. */
return(result);
}
/*===========================================================================*
* mini_send *
*===========================================================================*/
PRIVATE int mini_send(caller_ptr, dest, m_ptr, may_block)
register struct proc *caller_ptr; /* who is trying to send a message? */
int dest; /* to whom is message being sent? */
message *m_ptr; /* pointer to message buffer */
int may_block; /* (dis)allow blocking */
{
/* Send a message from 'caller_ptr' to 'dest'. If 'dest' is blocked waiting
* for this message, copy the message to it and unblock 'dest'. If 'dest' is
* not waiting at all, or is waiting for another source, queue 'caller_ptr'.
*/
register struct proc *dest_ptr, *next_ptr;
vir_bytes vb; /* message buffer pointer as vir_bytes */
vir_clicks vlo, vhi; /* virtual clicks containing message to send */
dest_ptr = proc_addr(dest); /* pointer to destination's proc entry */
#if ALLOW_GAP_MESSAGES
/* This check allows a message to be anywhere in data or stack or gap.
* It will have to be made more elaborate later for machines which
* don't have the gap mapped.
*/
vb = (vir_bytes) m_ptr;
vlo = vb >> CLICK_SHIFT; /* vir click for bottom of message */
vhi = (vb + MESS_SIZE - 1) >> CLICK_SHIFT; /* vir click for top of msg */
if (vlo < caller_ptr->p_memmap[D].mem_vir || vlo > vhi ||
vhi >= caller_ptr->p_memmap[S].mem_vir + caller_ptr->p_memmap[S].mem_len)
return(EFAULT);
#else
/* Check for messages wrapping around top of memory or outside data seg. */
vb = (vir_bytes) m_ptr;
vlo = vb >> CLICK_SHIFT; /* vir click for bottom of message */
vhi = (vb + MESS_SIZE - 1) >> CLICK_SHIFT; /* vir click for top of msg */
if (vhi < vlo ||
vhi - caller_ptr->p_memmap[D].mem_vir >= caller_ptr->p_memmap[D].mem_len)
return(EFAULT);
#endif
/* Check for deadlock by 'caller_ptr' and 'dest' sending to each other. */
if (dest_ptr->p_flags & SENDING) {
next_ptr = proc_addr(dest_ptr->p_sendto);
while (TRUE) {
if (next_ptr == caller_ptr) return(ELOCKED);
if (next_ptr->p_flags & SENDING)
next_ptr = proc_addr(next_ptr->p_sendto);
else
break;
}
}
/* Check to see if 'dest' is blocked waiting for this message. */
if ( (dest_ptr->p_flags & (RECEIVING | SENDING)) == RECEIVING &&
(dest_ptr->p_getfrom == ANY ||
dest_ptr->p_getfrom == proc_number(caller_ptr))) {
/* Destination is indeed waiting for this message. */
CopyMess(proc_number(caller_ptr), caller_ptr, m_ptr, dest_ptr,
dest_ptr->p_messbuf);
dest_ptr->p_flags &= ~RECEIVING; /* deblock destination */
if (dest_ptr->p_flags == 0) ready(dest_ptr);
} else if (may_block) {
/* Destination is not waiting. Block and queue caller. */
caller_ptr->p_messbuf = m_ptr;
if (caller_ptr->p_flags == 0) unready(caller_ptr);
caller_ptr->p_flags |= SENDING;
caller_ptr->p_sendto= dest;
/* Process is now blocked. Put in on the destination's queue. */
if ( (next_ptr = dest_ptr->p_callerq) == NIL_PROC)
dest_ptr->p_callerq = caller_ptr;
else {
while (next_ptr->p_sendlink != NIL_PROC)
next_ptr = next_ptr->p_sendlink;
next_ptr->p_sendlink = caller_ptr;
}
caller_ptr->p_sendlink = NIL_PROC;
} else {
return(ENOTREADY);
}
return(OK);
}
/*===========================================================================*
* mini_rec *
*===========================================================================*/
PRIVATE int mini_rec(caller_ptr, src, m_ptr, may_block)
register struct proc *caller_ptr; /* process trying to get message */
int src; /* which message source is wanted */
message *m_ptr; /* pointer to message buffer */
int may_block; /* (dis)allow blocking */
{
/* A process or task wants to get a message. If one is already queued,
* acquire it and deblock the sender. If no message from the desired source
* is available, block the caller.
*/
register struct proc *sender_ptr;
register struct proc *previous_ptr;
message m;
int i;
/* Check to see if a message from desired source is already available. */
if (!(caller_ptr->p_flags & SENDING)) {
/* Check caller queue. */
for (sender_ptr = caller_ptr->p_callerq; sender_ptr != NIL_PROC;
previous_ptr = sender_ptr, sender_ptr = sender_ptr->p_sendlink) {
if (src == ANY || src == proc_number(sender_ptr)) {
/* An acceptable message has been found. */
CopyMess(proc_number(sender_ptr), sender_ptr,
sender_ptr->p_messbuf, caller_ptr, m_ptr);
if (sender_ptr == caller_ptr->p_callerq)
caller_ptr->p_callerq = sender_ptr->p_sendlink;
else
previous_ptr->p_sendlink = sender_ptr->p_sendlink;
if ((sender_ptr->p_flags &= ~SENDING) == 0)
ready(sender_ptr); /* deblock sender */
return(OK);
}
}
/* Check bit mask for blocked notifications. If multiple bits are set,
* send the first notification encountered; the rest is handled later.
* This effectively prioritizes notifications. Notification also have
* priority of other messages.
*/
if (caller_ptr->p_ntf_blocked && isrxhardware(src)) {
for (i=0; i<NR_NOTIFICATIONS; i++) {
if (isset_bit(caller_ptr->p_ntf_blocked, i)) {
m.m_source = HARDWARE;
m.m_type = NOTIFICATION + i;
CopyMess(HARDWARE, proc_addr(HARDWARE), &m, caller_ptr, m_ptr);
clear_bit(caller_ptr->p_ntf_blocked, i);
return(OK);
}
}
}
}
/* No suitable message is available. Block the process trying to receive,
* unless this is not allowed by the system call.
*/
if (may_block) {
caller_ptr->p_getfrom = src;
caller_ptr->p_messbuf = m_ptr;
if (caller_ptr->p_flags == 0) unready(caller_ptr);
caller_ptr->p_flags |= RECEIVING;
return(OK);
} else {
return(ENOTREADY);
}
}
/*===========================================================================*
* pick_proc *
*===========================================================================*/
PRIVATE void pick_proc()
{
/* Decide who to run now. A new process is selected by setting 'proc_ptr'.
* When a fresh user (or idle) process is selected, record it in 'bill_ptr',
* so the clock task can tell who to bill for system time.
*/
register struct proc *rp; /* process to run */
int q; /* iterate over queues */
/* Check each of the scheduling queues for ready processes. The number of
* queues is defined in proc.h, and priorities are set in the task table.
* The lowest queue contains IDLE, which is always ready.
*/
for (q=0; q < NR_SCHED_QUEUES; q++) {
if ( (rp = rdy_head[q]) != NIL_PROC) {
proc_ptr = rp; /* run process 'rp' next */
if (isuserp(rp) || isidlep(rp)) /* possible bill 'rp' */
bill_ptr = rp;
return;
}
}
}
/*===========================================================================*
* ready *
*===========================================================================*/
PRIVATE void ready(rp)
register struct proc *rp; /* this process is now runnable */
{
/* Add 'rp' to one of the queues of runnable processes. */
int q = rp->p_priority; /* scheduling queue to use */
/* Processes, in principle, are added to the end of the queue. However,
* user processes are added in front of the queue, because this is a bit
* fairer to I/O bound processes.
*/
if (isuserp(rp)) { /* add to front of queue */
if (rdy_head[q] == NIL_PROC)
rdy_tail[q] = rp;
rp->p_nextready = rdy_head[q]; /* add to front of queue */
rdy_head[q] = rp;
}
else {
if (rdy_head[q] != NIL_PROC)
rdy_tail[q]->p_nextready = rp; /* add to end of queue */
else
rdy_head[q] = rp; /* add to empty queue */
rdy_tail[q] = rp;
rp->p_nextready = NIL_PROC;
}
/* Run 'rp' next if it has a higher priority than 'proc_ptr'. This actually
* should be done via pick_proc(), but mini_send() and mini_rec() rely
* on this side-effect.
*/
if (rp->p_priority < proc_ptr->p_priority) proc_ptr = rp;
}
/*===========================================================================*
* unready *
*===========================================================================*/
PRIVATE void unready(rp)
register struct proc *rp; /* this process is no longer runnable */
{
/* A process has blocked. See ready for a description of the queues. */
register struct proc *xp;
register struct proc **qtail; /* queue's rdy_tail */
int q = rp->p_priority; /* queue to use */
/* Side-effect for tasks: check if the task's stack still is ok? */
if (istaskp(rp)) {
if (*rp->p_stguard != STACK_GUARD)
panic("stack overrun by task", proc_number(rp));
}
/* Now make sure that the process is not in its ready queue. Remove the
* process if it is found. The easy part is to check the front of the queue.
*/
if ( (xp = rdy_head[q]) == NIL_PROC) return;
if (xp == rp) {
rdy_head[q] = xp->p_nextready; /* remove head of queue */
if (rp == proc_ptr) /* current process removed */
pick_proc(); /* pick new process to run */
return;
}
/* No match yet. Search body of queue. A process can be made unready even
* if it is not running by being sent a signal that kills it.
*/
while (xp->p_nextready != rp)
if ( (xp = xp->p_nextready) == NIL_PROC) return;
xp->p_nextready = xp->p_nextready->p_nextready;
qtail = &rdy_tail[q];
if (*qtail == rp) *qtail = xp;
}
/*===========================================================================*
* sched *
*===========================================================================*/
PRIVATE void sched()
{
/* The current process has run too long. If another low priority (user)
* process is runnable, put the current process on the end of the user queue,
* possibly promoting another user to head of the queue.
*/
if (rdy_head[PPRI_USER] == NIL_PROC) return;
/* One or more user processes queued. */
rdy_tail[PPRI_USER]->p_nextready = rdy_head[PPRI_USER];
rdy_tail[PPRI_USER] = rdy_head[PPRI_USER];
rdy_head[PPRI_USER] = rdy_head[PPRI_USER]->p_nextready;
rdy_tail[PPRI_USER]->p_nextready = NIL_PROC;
pick_proc();
}
/*==========================================================================*
* lock_pick_proc *
*==========================================================================*/
PUBLIC void lock_pick_proc()
{
/* Safe gateway to pick_proc() for tasks. */
switching = TRUE;
pick_proc();
switching = FALSE;
}
/*==========================================================================*
* lock_ready *
*==========================================================================*/
PUBLIC void lock_ready(rp)
struct proc *rp; /* this process is now runnable */
{
/* Safe gateway to ready() for tasks. */
switching = TRUE;
ready(rp);
switching = FALSE;
}
/*==========================================================================*
* lock_unready *
*==========================================================================*/
PUBLIC void lock_unready(rp)
struct proc *rp; /* this process is no longer runnable */
{
/* Safe gateway to unready() for tasks. */
switching = TRUE;
unready(rp);
switching = FALSE;
}
/*==========================================================================*
* lock_sched *
*==========================================================================*/
PUBLIC void lock_sched()
{
/* Safe gateway to sched() for tasks. */
switching = TRUE;
sched();
switching = FALSE;
}
/*==========================================================================*
* unhold *
*==========================================================================*/
PUBLIC void unhold()
{
/* Flush any held-up notifications. 'k_reenter' must be 0. 'held_head' must
* not be NIL_PROC. Interrupts must be disabled. They will be enabled but
* will be disabled when this returns.
*/
register struct proc *rp; /* current head of held queue */
int i;
if (switching) return;
rp = held_head;
do {
for (i=0; i<NR_NOTIFICATIONS; i++) {
if (isset_bit(rp->p_ntf_held,i)) {
clear_bit(rp->p_ntf_held,i);
if (! rp->p_ntf_held) /* proceed to next in queue? */
if ( (held_head = rp->p_ntf_nextheld) == NIL_PROC)
held_tail = NIL_PROC;
unlock(); /* reduce latency; held queue may change! */
notify(proc_number(rp), NOTIFICATION + i);
lock(); /* protect the held queue again */
}
}
}
while ( (rp = held_head) != NIL_PROC);
}
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