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minix/kernel/proc.c
Ben Gras 41e9fedf87 Mostly bugfixes of bugs triggered by the test set. 
bugfixes:
 SYSTEM:
 . removed
        rc->p_priv->s_flags = 0;
   for the priv struct shared by all user processes in get_priv(). this
   should only be done once. doing a SYS_PRIV_USER in sys_privctl()
   caused the flags of all user processes to be reset, so they were no
   longer PREEMPTIBLE. this happened when RS executed a policy script.
   (this broke test1 in the test set)

 VFS/MFS:
 . chown can change the mode of a file, and chmod arguments are only
   part of the full file mode so the full filemode is slightly magic.
   changed these calls so that the final modes are returned to VFS, so
   that the vnode can be kept up-to-date.
   (this broke test11 in the test set)

 MFS:
 . lookup() checked for sizeof(string) instead of sizeof(user_path),
   truncating long path names
   (caught by test 23)
 . truncate functions neglected to update ctime
   (this broke test16)

 VFS:
 . corner case of an empty filename lookup caused fields of a request
   not to be filled in in the lookup functions, not making it clear
   that the lookup had failed, causing messages to garbage processes,
   causing strange failures.
   (caught by test 30)
 . trust v_size in vnode when doing reads or writes on non-special
   files, truncating i/o where necessary; this is necessary for pipes,
   as MFS can't tell when a pipe has been truncated without it being
   told explicitly each time.
   when the last reader/writer on a pipe closes, tell FS about
   the new size using truncate_vn().
   (this broke test 25, among others)
 . permission check for chdir() had disappeared; added a
   forbidden() call
   (caught by test 23)

new code, shouldn't change anything:
 . introduced RTS_SET, RTS_UNSET, and RTS_ISSET macro's, and their
   LOCK variants. These macros set and clear the p_rts_flags field,
   causing a lot of duplicated logic like

       old_flags = rp->p_rts_flags;            /* save value of the flags */
       rp->p_rts_flags &= ~NO_PRIV;
       if (old_flags != 0 && rp->p_rts_flags == 0) lock_enqueue(rp);

   to change into the simpler

       RTS_LOCK_UNSET(rp, NO_PRIV);

   so the macros take care of calling dequeue() and enqueue() (or lock_*()),
   as the case may be). This makes the code a bit more readable and a
   bit less fragile.
 . removed return code from do_clocktick in CLOCK as it currently
   never replies
 . removed some debug code from VFS
 . fixed grant debug message in device.c
 
preemptive checks, tests, changes:
 . added return code checks of receive() to SYSTEM and CLOCK
 . O_TRUNC should never arrive at MFS (added sanity check and removed
   O_TRUNC code)
 . user_path declared with PATH_MAX+1 to let it be null-terminated
 . checks in MFS to see if strings passed by VFS are null-terminated
 
 IS:
 . static irq name table thrown out
2007-02-01 17:50:02 +00:00

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/* This file contains essentially all of the process and message handling.
* Together with "mpx.s" it forms the lowest layer of the MINIX kernel.
* There is one entry point from the outside:
*
* sys_call: a system call, i.e., the kernel is trapped with an INT
*
* As well as several entry points used from the interrupt and task level:
*
* lock_notify: notify a process of a system event
* lock_send: send a message to a process
* lock_enqueue: put a process on one of the scheduling queues
* lock_dequeue: remove a process from the scheduling queues
*
* Changes:
* Aug 19, 2005 rewrote scheduling code (Jorrit N. Herder)
* Jul 25, 2005 rewrote system call handling (Jorrit N. Herder)
* May 26, 2005 rewrote message passing functions (Jorrit N. Herder)
* May 24, 2005 new notification system call (Jorrit N. Herder)
* Oct 28, 2004 nonblocking send and receive calls (Jorrit N. Herder)
*
* The code here is critical to make everything work and is important for the
* overall performance of the system. A large fraction of the code deals with
* list manipulation. To make this both easy to understand and fast to execute
* pointer pointers are used throughout the code. Pointer pointers prevent
* exceptions for the head or tail of a linked list.
*
* node_t *queue, *new_node; // assume these as global variables
* node_t **xpp = &queue; // get pointer pointer to head of queue
* while (*xpp != NULL) // find last pointer of the linked list
* xpp = &(*xpp)->next; // get pointer to next pointer
* *xpp = new_node; // now replace the end (the NULL pointer)
* new_node->next = NULL; // and mark the new end of the list
*
* For example, when adding a new node to the end of the list, one normally
* makes an exception for an empty list and looks up the end of the list for
* nonempty lists. As shown above, this is not required with pointer pointers.
*/
#include <minix/com.h>
#include <minix/callnr.h>
#include <minix/endpoint.h>
#include "debug.h"
#include "kernel.h"
#include "proc.h"
#include <signal.h>
#include <minix/portio.h>
/* Scheduling and message passing functions. The functions are available to
* other parts of the kernel through lock_...(). The lock temporarily disables
* interrupts to prevent race conditions.
*/
FORWARD _PROTOTYPE( int mini_send, (struct proc *caller_ptr, int dst_e,
message *m_ptr, unsigned flags));
FORWARD _PROTOTYPE( int mini_receive, (struct proc *caller_ptr, int src,
message *m_ptr, unsigned flags));
FORWARD _PROTOTYPE( int mini_notify, (struct proc *caller_ptr, int dst));
FORWARD _PROTOTYPE( int deadlock, (int function,
register struct proc *caller, int src_dst));
FORWARD _PROTOTYPE( void enqueue, (struct proc *rp));
FORWARD _PROTOTYPE( void dequeue, (struct proc *rp));
FORWARD _PROTOTYPE( void sched, (struct proc *rp, int *queue, int *front));
FORWARD _PROTOTYPE( void pick_proc, (void));
#define BuildMess(m_ptr, src, dst_ptr) \
(m_ptr)->m_source = proc_addr(src)->p_endpoint; \
(m_ptr)->m_type = NOTIFY_FROM(src); \
(m_ptr)->NOTIFY_TIMESTAMP = get_uptime(); \
switch (src) { \
case HARDWARE: \
(m_ptr)->NOTIFY_ARG = priv(dst_ptr)->s_int_pending; \
priv(dst_ptr)->s_int_pending = 0; \
break; \
case SYSTEM: \
(m_ptr)->NOTIFY_ARG = priv(dst_ptr)->s_sig_pending; \
priv(dst_ptr)->s_sig_pending = 0; \
break; \
}
#define CopyMess(s,sp,sm,dp,dm) \
cp_mess(proc_addr(s)->p_endpoint, \
(sp)->p_memmap[D].mem_phys, \
(vir_bytes)sm, (dp)->p_memmap[D].mem_phys, (vir_bytes)dm)
/*===========================================================================*
* sys_call *
*===========================================================================*/
PUBLIC int sys_call(call_nr, src_dst_e, m_ptr, bit_map)
int call_nr; /* system call number and flags */
int src_dst_e; /* src to receive from or dst to send to */
message *m_ptr; /* pointer to message in the caller's space */
long bit_map; /* notification event set or flags */
{
/* 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 */
unsigned flags = call_nr & SYSCALL_FLAGS; /* get flags */
int mask_entry; /* bit to check in send mask */
int group_size; /* used for deadlock check */
int result; /* the system call's result */
int src_dst;
vir_clicks vlo, vhi; /* virtual clicks containing message to send */
#if 1
if (RTS_ISSET(caller_ptr, SLOT_FREE))
{
kprintf("called by the dead?!?\n");
return EINVAL;
}
#endif
/* Require a valid source and/ or destination process, unless echoing. */
if (src_dst_e != ANY && function != ECHO) {
if(!isokendpt(src_dst_e, &src_dst)) {
#if DEBUG_ENABLE_IPC_WARNINGS
kprintf("sys_call: trap %d by %d with bad endpoint %d\n",
function, proc_nr(caller_ptr), src_dst_e);
#endif
return EDEADSRCDST;
}
} else src_dst = src_dst_e;
/* Check if the process has privileges for the requested call. Calls to the
* kernel may only be SENDREC, because tasks always reply and may not block
* if the caller doesn't do receive().
*/
if (! (priv(caller_ptr)->s_trap_mask & (1 << function)) ||
(iskerneln(src_dst) && function != SENDREC
&& function != RECEIVE)) {
#if DEBUG_ENABLE_IPC_WARNINGS
kprintf("sys_call: trap %d not allowed, caller %d, src_dst %d\n",
function, proc_nr(caller_ptr), src_dst);
#endif
return(ETRAPDENIED); /* trap denied by mask or kernel */
}
/* If the call involves a message buffer, i.e., for SEND, RECEIVE, SENDREC,
* or ECHO, check the message pointer. This check allows a message to be
* anywhere in data or stack or gap. It will have to be made more elaborate
* for machines which don't have the gap mapped.
*/
if (function & CHECK_PTR) {
vlo = (vir_bytes) m_ptr >> CLICK_SHIFT;
vhi = ((vir_bytes) m_ptr + MESS_SIZE - 1) >> CLICK_SHIFT;
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) {
#if DEBUG_ENABLE_IPC_WARNINGS
kprintf("sys_call: invalid message pointer, trap %d, caller %d\n",
function, proc_nr(caller_ptr));
#endif
return(EFAULT); /* invalid message pointer */
}
}
/* If the call is to send to a process, i.e., for SEND, SENDREC or NOTIFY,
* verify that the caller is allowed to send to the given destination.
*/
if (function & CHECK_DST) {
if (! get_sys_bit(priv(caller_ptr)->s_ipc_to, nr_to_id(src_dst))) {
#if DEBUG_ENABLE_IPC_WARNINGS
kprintf("sys_call: ipc mask denied trap %d from %d to %d\n",
function, proc_nr(caller_ptr), src_dst);
#endif
return(ECALLDENIED); /* call denied by ipc mask */
}
}
/* Check for a possible deadlock for blocking SEND(REC) and RECEIVE. */
if (function & CHECK_DEADLOCK) {
if (group_size = deadlock(function, caller_ptr, src_dst)) {
#if DEBUG_ENABLE_IPC_WARNINGS
kprintf("sys_call: trap %d from %d to %d deadlocked, group size %d\n",
function, proc_nr(caller_ptr), src_dst, group_size);
#endif
return(ELOCKED);
}
}
/* 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.
* - SENDREC: combines SEND and RECEIVE in a single system call
* - SEND: sender blocks until its message has been delivered
* - RECEIVE: receiver blocks until an acceptable message has arrived
* - NOTIFY: nonblocking call; deliver notification or mark pending
* - ECHO: nonblocking call; directly echo back the message
*/
switch(function) {
case SENDREC:
/* A flag is set so that notifications cannot interrupt SENDREC. */
caller_ptr->p_misc_flags |= REPLY_PENDING;
/* fall through */
case SEND:
result = mini_send(caller_ptr, src_dst_e, m_ptr, flags);
if (function == SEND || result != OK) {
break; /* done, or SEND failed */
} /* fall through for SENDREC */
case RECEIVE:
if (function == RECEIVE)
caller_ptr->p_misc_flags &= ~REPLY_PENDING;
result = mini_receive(caller_ptr, src_dst_e, m_ptr, flags);
break;
case NOTIFY:
result = mini_notify(caller_ptr, src_dst);
break;
case ECHO:
CopyMess(caller_ptr->p_nr, caller_ptr, m_ptr, caller_ptr, m_ptr);
result = OK;
break;
default:
result = EBADCALL; /* illegal system call */
}
/* Now, return the result of the system call to the caller. */
return(result);
}
/*===========================================================================*
* deadlock *
*===========================================================================*/
PRIVATE int deadlock(function, cp, src_dst)
int function; /* trap number */
register struct proc *cp; /* pointer to caller */
int src_dst; /* src or dst process */
{
/* Check for deadlock. This can happen if 'caller_ptr' and 'src_dst' have
* a cyclic dependency of blocking send and receive calls. The only cyclic
* depency that is not fatal is if the caller and target directly SEND(REC)
* and RECEIVE to each other. If a deadlock is found, the group size is
* returned. Otherwise zero is returned.
*/
register struct proc *xp; /* process pointer */
int group_size = 1; /* start with only caller */
int trap_flags;
while (src_dst != ANY) { /* check while process nr */
int src_dst_e;
xp = proc_addr(src_dst); /* follow chain of processes */
group_size ++; /* extra process in group */
/* Check whether the last process in the chain has a dependency. If it
* has not, the cycle cannot be closed and we are done.
*/
if (RTS_ISSET(xp, RECEIVING)) { /* xp has dependency */
if(xp->p_getfrom_e == ANY) src_dst = ANY;
else okendpt(xp->p_getfrom_e, &src_dst);
} else if (RTS_ISSET(xp, SENDING)) { /* xp has dependency */
okendpt(xp->p_sendto_e, &src_dst);
} else {
return(0); /* not a deadlock */
}
/* Now check if there is a cyclic dependency. For group sizes of two,
* a combination of SEND(REC) and RECEIVE is not fatal. Larger groups
* or other combinations indicate a deadlock.
*/
if (src_dst == proc_nr(cp)) { /* possible deadlock */
if (group_size == 2) { /* caller and src_dst */
/* The function number is magically converted to flags. */
if ((xp->p_rts_flags ^ (function << 2)) & SENDING) {
return(0); /* not a deadlock */
}
}
return(group_size); /* deadlock found */
}
}
return(0); /* not a deadlock */
}
/*===========================================================================*
* mini_send *
*===========================================================================*/
PRIVATE int mini_send(caller_ptr, dst_e, m_ptr, flags)
register struct proc *caller_ptr; /* who is trying to send a message? */
int dst_e; /* to whom is message being sent? */
message *m_ptr; /* pointer to message buffer */
unsigned flags; /* system call flags */
{
/* Send a message from 'caller_ptr' to 'dst'. If 'dst' is blocked waiting
* for this message, copy the message to it and unblock 'dst'. If 'dst' is
* not waiting at all, or is waiting for another source, queue 'caller_ptr'.
*/
register struct proc *dst_ptr;
register struct proc **xpp;
int dst_p;
dst_p = _ENDPOINT_P(dst_e);
dst_ptr = proc_addr(dst_p);
if (RTS_ISSET(dst_ptr, NO_ENDPOINT)) return EDSTDIED;
/* Check if 'dst' is blocked waiting for this message. The destination's
* SENDING flag may be set when its SENDREC call blocked while sending.
*/
if ( (RTS_ISSET(dst_ptr, RECEIVING) && !RTS_ISSET(dst_ptr, SENDING)) &&
(dst_ptr->p_getfrom_e == ANY
|| dst_ptr->p_getfrom_e == caller_ptr->p_endpoint)) {
/* Destination is indeed waiting for this message. */
CopyMess(caller_ptr->p_nr, caller_ptr, m_ptr, dst_ptr,
dst_ptr->p_messbuf);
RTS_UNSET(dst_ptr, RECEIVING);
} else if ( ! (flags & NON_BLOCKING)) {
/* Destination is not waiting. Block and dequeue caller. */
caller_ptr->p_messbuf = m_ptr;
RTS_SET(caller_ptr, SENDING);
caller_ptr->p_sendto_e = dst_e;
/* Process is now blocked. Put in on the destination's queue. */
xpp = &dst_ptr->p_caller_q; /* find end of list */
while (*xpp != NIL_PROC) xpp = &(*xpp)->p_q_link;
*xpp = caller_ptr; /* add caller to end */
caller_ptr->p_q_link = NIL_PROC; /* mark new end of list */
} else {
return(ENOTREADY);
}
return(OK);
}
/*===========================================================================*
* mini_receive *
*===========================================================================*/
PRIVATE int mini_receive(caller_ptr, src_e, m_ptr, flags)
register struct proc *caller_ptr; /* process trying to get message */
int src_e; /* which message source is wanted */
message *m_ptr; /* pointer to message buffer */
unsigned flags; /* system call flags */
{
/* A process or task wants to get a message. If a message is already queued,
* acquire it and deblock the sender. If no message from the desired source
* is available block the caller, unless the flags don't allow blocking.
*/
register struct proc **xpp;
register struct notification **ntf_q_pp;
message m;
int bit_nr;
sys_map_t *map;
bitchunk_t *chunk;
int i, src_id, src_proc_nr, src_p;
if(src_e == ANY) src_p = ANY;
else
{
okendpt(src_e, &src_p);
if (RTS_ISSET(proc_addr(src_p), NO_ENDPOINT)) return ESRCDIED;
}
/* Check to see if a message from desired source is already available.
* The caller's SENDING flag may be set if SENDREC couldn't send. If it is
* set, the process should be blocked.
*/
if (!RTS_ISSET(caller_ptr, SENDING)) {
/* Check if there are pending notifications, except for SENDREC. */
if (! (caller_ptr->p_misc_flags & REPLY_PENDING)) {
map = &priv(caller_ptr)->s_notify_pending;
for (chunk=&map->chunk[0]; chunk<&map->chunk[NR_SYS_CHUNKS]; chunk++) {
/* Find a pending notification from the requested source. */
if (! *chunk) continue; /* no bits in chunk */
for (i=0; ! (*chunk & (1<<i)); ++i) {} /* look up the bit */
src_id = (chunk - &map->chunk[0]) * BITCHUNK_BITS + i;
if (src_id >= NR_SYS_PROCS) break; /* out of range */
src_proc_nr = id_to_nr(src_id); /* get source proc */
#if DEBUG_ENABLE_IPC_WARNINGS
if(src_proc_nr == NONE) {
kprintf("mini_receive: sending notify from NONE\n");
}
#endif
if (src_e!=ANY && src_p != src_proc_nr) continue;/* source not ok */
*chunk &= ~(1 << i); /* no longer pending */
/* Found a suitable source, deliver the notification message. */
BuildMess(&m, src_proc_nr, caller_ptr); /* assemble message */
CopyMess(src_proc_nr, proc_addr(HARDWARE), &m, caller_ptr, m_ptr);
return(OK); /* report success */
}
}
/* Check caller queue. Use pointer pointers to keep code simple. */
xpp = &caller_ptr->p_caller_q;
while (*xpp != NIL_PROC) {
if (src_e == ANY || src_p == proc_nr(*xpp)) {
#if 1
if (RTS_ISSET(*xpp, SLOT_FREE))
{
kprintf("listening to the dead?!?\n");
return EINVAL;
}
#endif
/* Found acceptable message. Copy it and update status. */
CopyMess((*xpp)->p_nr, *xpp, (*xpp)->p_messbuf, caller_ptr, m_ptr);
RTS_UNSET(*xpp, SENDING);
*xpp = (*xpp)->p_q_link; /* remove from queue */
return(OK); /* report success */
}
xpp = &(*xpp)->p_q_link; /* proceed to next */
}
}
/* No suitable message is available or the caller couldn't send in SENDREC.
* Block the process trying to receive, unless the flags tell otherwise.
*/
if ( ! (flags & NON_BLOCKING)) {
caller_ptr->p_getfrom_e = src_e;
caller_ptr->p_messbuf = m_ptr;
RTS_SET(caller_ptr, RECEIVING);
return(OK);
} else {
return(ENOTREADY);
}
}
/*===========================================================================*
* mini_notify *
*===========================================================================*/
PRIVATE int mini_notify(caller_ptr, dst)
register struct proc *caller_ptr; /* sender of the notification */
int dst; /* which process to notify */
{
register struct proc *dst_ptr = proc_addr(dst);
int src_id; /* source id for late delivery */
message m; /* the notification message */
/* Check to see if target is blocked waiting for this message. A process
* can be both sending and receiving during a SENDREC system call.
*/
if ( (RTS_ISSET(dst_ptr, RECEIVING) && !RTS_ISSET(dst_ptr, SENDING)) &&
! (dst_ptr->p_misc_flags & REPLY_PENDING) &&
(dst_ptr->p_getfrom_e == ANY ||
dst_ptr->p_getfrom_e == caller_ptr->p_endpoint)) {
/* Destination is indeed waiting for a message. Assemble a notification
* message and deliver it. Copy from pseudo-source HARDWARE, since the
* message is in the kernel's address space.
*/
BuildMess(&m, proc_nr(caller_ptr), dst_ptr);
CopyMess(proc_nr(caller_ptr), proc_addr(HARDWARE), &m,
dst_ptr, dst_ptr->p_messbuf);
RTS_UNSET(dst_ptr, RECEIVING);
return(OK);
}
/* Destination is not ready to receive the notification. Add it to the
* bit map with pending notifications. Note the indirectness: the system id
* instead of the process number is used in the pending bit map.
*/
src_id = priv(caller_ptr)->s_id;
set_sys_bit(priv(dst_ptr)->s_notify_pending, src_id);
return(OK);
}
/*===========================================================================*
* lock_notify *
*===========================================================================*/
PUBLIC int lock_notify(src_e, dst_e)
int src_e; /* (endpoint) sender of the notification */
int dst_e; /* (endpoint) who is to be notified */
{
/* Safe gateway to mini_notify() for tasks and interrupt handlers. The sender
* is explicitely given to prevent confusion where the call comes from. MINIX
* kernel is not reentrant, which means to interrupts are disabled after
* the first kernel entry (hardware interrupt, trap, or exception). Locking
* is done by temporarily disabling interrupts.
*/
int result, src, dst;
if(!isokendpt(src_e, &src) || !isokendpt(dst_e, &dst))
return EDEADSRCDST;
/* Exception or interrupt occurred, thus already locked. */
if (k_reenter >= 0) {
result = mini_notify(proc_addr(src), dst);
}
/* Call from task level, locking is required. */
else {
lock(0, "notify");
result = mini_notify(proc_addr(src), dst);
unlock(0);
}
return(result);
}
/*===========================================================================*
* enqueue *
*===========================================================================*/
PRIVATE void enqueue(rp)
register struct proc *rp; /* this process is now runnable */
{
/* Add 'rp' to one of the queues of runnable processes. This function is
* responsible for inserting a process into one of the scheduling queues.
* The mechanism is implemented here. The actual scheduling policy is
* defined in sched() and pick_proc().
*/
int q; /* scheduling queue to use */
int front; /* add to front or back */
#if DEBUG_SCHED_CHECK
check_runqueues("enqueue1");
if (rp->p_ready) kprintf("enqueue() already ready process\n");
#endif
/* Determine where to insert to process. */
sched(rp, &q, &front);
/* Now add the process to the queue. */
if (rdy_head[q] == NIL_PROC) { /* add to empty queue */
rdy_head[q] = rdy_tail[q] = rp; /* create a new queue */
rp->p_nextready = NIL_PROC; /* mark new end */
}
else if (front) { /* add to head of queue */
rp->p_nextready = rdy_head[q]; /* chain head of queue */
rdy_head[q] = rp; /* set new queue head */
}
else { /* add to tail of queue */
rdy_tail[q]->p_nextready = rp; /* chain tail of queue */
rdy_tail[q] = rp; /* set new queue tail */
rp->p_nextready = NIL_PROC; /* mark new end */
}
/* Now select the next process to run. */
pick_proc();
#if DEBUG_SCHED_CHECK
rp->p_ready = 1;
check_runqueues("enqueue2");
#endif
}
/*===========================================================================*
* dequeue *
*===========================================================================*/
PRIVATE void dequeue(rp)
register struct proc *rp; /* this process is no longer runnable */
{
/* A process must be removed from the scheduling queues, for example, because
* it has blocked. If the currently active process is removed, a new process
* is picked to run by calling pick_proc().
*/
register int q = rp->p_priority; /* queue to use */
register struct proc **xpp; /* iterate over queue */
register struct proc *prev_xp;
/* Side-effect for kernel: check if the task's stack still is ok? */
if (iskernelp(rp)) {
if (*priv(rp)->s_stack_guard != STACK_GUARD)
panic("stack overrun by task", proc_nr(rp));
}
#if DEBUG_SCHED_CHECK
check_runqueues("dequeue1");
if (! rp->p_ready) kprintf("%s:%d: dequeue() already unready process\n",
f_str, f_line);
#endif
/* Now make sure that the process is not in its ready queue. Remove the
* process if it is found. A process can be made unready even if it is not
* running by being sent a signal that kills it.
*/
prev_xp = NIL_PROC;
for (xpp = &rdy_head[q]; *xpp != NIL_PROC; xpp = &(*xpp)->p_nextready) {
if (*xpp == rp) { /* found process to remove */
*xpp = (*xpp)->p_nextready; /* replace with next chain */
if (rp == rdy_tail[q]) /* queue tail removed */
rdy_tail[q] = prev_xp; /* set new tail */
if (rp == proc_ptr || rp == next_ptr) /* active process removed */
pick_proc(); /* pick new process to run */
break;
}
prev_xp = *xpp; /* save previous in chain */
}
#if DEBUG_SCHED_CHECK
rp->p_ready = 0;
check_runqueues("dequeue2");
#endif
}
/*===========================================================================*
* sched *
*===========================================================================*/
PRIVATE void sched(rp, queue, front)
register struct proc *rp; /* process to be scheduled */
int *queue; /* return: queue to use */
int *front; /* return: front or back */
{
/* This function determines the scheduling policy. It is called whenever a
* process must be added to one of the scheduling queues to decide where to
* insert it. As a side-effect the process' priority may be updated.
*/
int time_left = (rp->p_ticks_left > 0); /* quantum fully consumed */
/* Check whether the process has time left. Otherwise give a new quantum
* and lower the process' priority, unless the process already is in the
* lowest queue.
*/
if (! time_left) { /* quantum consumed ? */
rp->p_ticks_left = rp->p_quantum_size; /* give new quantum */
if (rp->p_priority < (IDLE_Q-1)) {
rp->p_priority += 1; /* lower priority */
}
}
/* If there is time left, the process is added to the front of its queue,
* so that it can immediately run. The queue to use simply is always the
* process' current priority.
*/
*queue = rp->p_priority;
*front = time_left;
}
/*===========================================================================*
* pick_proc *
*===========================================================================*/
PRIVATE void pick_proc()
{
/* Decide who to run now. A new process is selected by setting 'next_ptr'.
* When a billable process is selected, record it in 'bill_ptr', so that 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) {
next_ptr = rp; /* run process 'rp' next */
if (priv(rp)->s_flags & BILLABLE)
bill_ptr = rp; /* bill for system time */
return;
}
}
}
/*===========================================================================*
* balance_queues *
*===========================================================================*/
#define Q_BALANCE_TICKS 100
PUBLIC void balance_queues(tp)
timer_t *tp; /* watchdog timer pointer */
{
/* Check entire process table and give all process a higher priority. This
* effectively means giving a new quantum. If a process already is at its
* maximum priority, its quantum will be renewed.
*/
static timer_t queue_timer; /* timer structure to use */
register struct proc* rp; /* process table pointer */
clock_t next_period; /* time of next period */
int ticks_added = 0; /* total time added */
for (rp=BEG_PROC_ADDR; rp<END_PROC_ADDR; rp++) {
if (! isemptyp(rp)) { /* check slot use */
lock(5,"balance_queues");
if (rp->p_priority > rp->p_max_priority) { /* update priority? */
if (rp->p_rts_flags == 0) dequeue(rp); /* take off queue */
ticks_added += rp->p_quantum_size; /* do accounting */
rp->p_priority -= 1; /* raise priority */
if (rp->p_rts_flags == 0) enqueue(rp); /* put on queue */
}
else {
ticks_added += rp->p_quantum_size - rp->p_ticks_left;
rp->p_ticks_left = rp->p_quantum_size; /* give new quantum */
}
unlock(5);
}
}
#if DEBUG
kprintf("ticks_added: %d\n", ticks_added);
#endif
/* Now schedule a new watchdog timer to balance the queues again. The
* period depends on the total amount of quantum ticks added.
*/
next_period = MAX(Q_BALANCE_TICKS, ticks_added); /* calculate next */
set_timer(&queue_timer, get_uptime() + next_period, balance_queues);
}
/*===========================================================================*
* lock_send *
*===========================================================================*/
PUBLIC int lock_send(dst_e, m_ptr)
int dst_e; /* to whom is message being sent? */
message *m_ptr; /* pointer to message buffer */
{
/* Safe gateway to mini_send() for tasks. */
int result;
lock(2, "send");
result = mini_send(proc_ptr, dst_e, m_ptr, NON_BLOCKING);
unlock(2);
return(result);
}
/*===========================================================================*
* lock_enqueue *
*===========================================================================*/
PUBLIC void lock_enqueue(rp)
struct proc *rp; /* this process is now runnable */
{
/* Safe gateway to enqueue() for tasks. */
lock(3, "enqueue");
enqueue(rp);
unlock(3);
}
/*===========================================================================*
* lock_dequeue *
*===========================================================================*/
PUBLIC void lock_dequeue(rp)
struct proc *rp; /* this process is no longer runnable */
{
/* Safe gateway to dequeue() for tasks. */
if (k_reenter >= 0) {
/* We're in an exception or interrupt, so don't lock (and ...
* don't unlock).
*/
dequeue(rp);
} else {
lock(4, "dequeue");
dequeue(rp);
unlock(4);
}
}
/*===========================================================================*
* isokendpt_f *
*===========================================================================*/
#if DEBUG_ENABLE_IPC_WARNINGS
PUBLIC int isokendpt_f(file, line, e, p, fatalflag)
char *file;
int line;
#else
PUBLIC int isokendpt_f(e, p, fatalflag)
#endif
endpoint_t e;
int *p, fatalflag;
{
int ok = 0;
/* Convert an endpoint number into a process number.
* Return nonzero if the process is alive with the corresponding
* generation number, zero otherwise.
*
* This function is called with file and line number by the
* isokendpt_d macro if DEBUG_ENABLE_IPC_WARNINGS is defined,
* otherwise without. This allows us to print the where the
* conversion was attempted, making the errors verbose without
* adding code for that at every call.
*
* If fatalflag is nonzero, we must panic if the conversion doesn't
* succeed.
*/
*p = _ENDPOINT_P(e);
if(!isokprocn(*p)) {
#if DEBUG_ENABLE_IPC_WARNINGS
kprintf("kernel:%s:%d: bad endpoint %d: proc %d out of range\n",
file, line, e, *p);
#endif
} else if(isemptyn(*p)) {
#if DEBUG_ENABLE_IPC_WARNINGS
kprintf("kernel:%s:%d: bad endpoint %d: proc %d empty\n", file, line, e, *p);
#endif
} else if(proc_addr(*p)->p_endpoint != e) {
#if DEBUG_ENABLE_IPC_WARNINGS
kprintf("kernel:%s:%d: bad endpoint %d: proc %d has ept %d (generation %d vs. %d)\n", file, line,
e, *p, proc_addr(*p)->p_endpoint,
_ENDPOINT_G(e), _ENDPOINT_G(proc_addr(*p)->p_endpoint));
#endif
} else ok = 1;
if(!ok && fatalflag) {
panic("invalid endpoint ", e);
}
return ok;
}
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