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minix/kernel/proc.c
Ben Gras cd8b915ed9 Primary goal for these changes is: 
- no longer have kernel have its own page table that is loaded
    on every kernel entry (trap, interrupt, exception). the primary
    purpose is to reduce the number of required reloads.
Result:
  - kernel can only access memory of process that was running when
    kernel was entered
  - kernel must be mapped into every process page table, so traps to
    kernel keep working
Problem:
  - kernel must often access memory of arbitrary processes (e.g. send
    arbitrary processes messages); this can't happen directly any more;
    usually because that process' page table isn't loaded at all, sometimes
    because that memory isn't mapped in at all, sometimes because it isn't
    mapped in read-write.
So:
  - kernel must be able to map in memory of any process, in its own
    address space.
Implementation:
  - VM and kernel share a range of memory in which addresses of
    all page tables of all processes are available. This has two purposes:
      . Kernel has to know what data to copy in order to map in a range
      . Kernel has to know where to write the data in order to map it in
    That last point is because kernel has to write in the currently loaded
    page table.
  - Processes and kernel are separated through segments; kernel segments
    haven't changed.
  - The kernel keeps the process whose page table is currently loaded
    in 'ptproc.'
  - If it wants to map in a range of memory, it writes the value of the
    page directory entry for that range into the page directory entry
    in the currently loaded map. There is a slot reserved for such
    purposes. The kernel can then access this memory directly.
  - In order to do this, its segment has been increased (and the
    segments of processes start where it ends).
  - In the pagefault handler, detect if the kernel is doing
    'trappable' memory access (i.e. a pagefault isn't a fatal
     error) and if so,
       - set the saved instruction pointer to phys_copy_fault,
	 breaking out of phys_copy
       - set the saved eax register to the address of the page
	 fault, both for sanity checking and for checking in
	 which of the two ranges that phys_copy was called
	 with the fault occured
  - Some boot-time processes do not have their own page table,
    and are mapped in with the kernel, and separated with
    segments. The kernel detects this using HASPT. If such a
    process has to be scheduled, any page table will work and
    no page table switch is done.

Major changes in kernel are
  - When accessing user processes memory, kernel no longer
    explicitly checks before it does so if that memory is OK.
    It simply makes the mapping (if necessary), tries to do the
    operation, and traps the pagefault if that memory isn't present;
    if that happens, the copy function returns EFAULT.
    So all of the CHECKRANGE_OR_SUSPEND macros are gone.
  - Kernel no longer has to copy/read and parse page tables.
  - A message copying optimisation: when messages are copied, and
    the recipient isn't mapped in, they are copied into a buffer
    in the kernel. This is done in QueueMess. The next time
    the recipient is scheduled, this message is copied into
    its memory. This happens in schedcheck().
    This eliminates the mapping/copying step for messages, and makes
    it easier to deliver messages. This eliminates soft_notify.
  - Kernel no longer creates a page table at all, so the vm_setbuf
    and pagetable writing in memory.c is gone.

Minor changes in kernel are
  - ipc_stats thrown out, wasn't used
  - misc flags all renamed to MF_*
  - NOREC_* macros to enter and leave functions that should not
    be called recursively; just sanity checks really
  - code to fully decode segment selectors and descriptors
    to print on exceptions
  - lots of vmassert()s added, only executed if DEBUG_VMASSERT is 1
2009-09-21 14:31:52 +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_send: send a message to a process
*
* 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 <stddef.h>
#include <signal.h>
#include <minix/portio.h>
#include <minix/u64.h>
#include "debug.h"
#include "kernel.h"
#include "proc.h"
#include "vm.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, int flags));
FORWARD _PROTOTYPE( int mini_receive, (struct proc *caller_ptr, int src,
message *m_ptr, int flags));
FORWARD _PROTOTYPE( int mini_senda, (struct proc *caller_ptr,
asynmsg_t *table, size_t size));
FORWARD _PROTOTYPE( int deadlock, (int function,
register struct proc *caller, int src_dst));
FORWARD _PROTOTYPE( int try_async, (struct proc *caller_ptr));
FORWARD _PROTOTYPE( int try_one, (struct proc *src_ptr, struct proc *dst_ptr));
FORWARD _PROTOTYPE( void sched, (struct proc *rp, int *queue, int *front));
FORWARD _PROTOTYPE( void pick_proc, (void));
#define PICK_ANY 1
#define PICK_HIGHERONLY 2
#define BuildNotifyMessage(m_ptr, src, dst_ptr) \
(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; \
}
/*===========================================================================*
* QueueMess *
*===========================================================================*/
PRIVATE int QueueMess(endpoint_t ep, vir_bytes msg_lin, struct proc *dst)
{
int k;
phys_bytes addr;
NOREC_ENTER(queuemess);
/* Queue a message from the src process (in memory) to the dst
* process (using dst process table entry). Do actual copy to
* kernel here; it's an error if the copy fails into kernel.
*/
vmassert(!(dst->p_misc_flags & MF_DELIVERMSG));
vmassert(dst->p_delivermsg_lin);
vmassert(isokendpt(ep, &k));
#if 0
if(INMEMORY(dst)) {
PHYS_COPY_CATCH(msg_lin, dst->p_delivermsg_lin,
sizeof(message), addr);
if(!addr) {
PHYS_COPY_CATCH(vir2phys(&ep), dst->p_delivermsg_lin,
sizeof(ep), addr);
if(!addr) {
NOREC_RETURN(queuemess, OK);
}
}
}
#else
FIXME("in-memory process copy");
#endif
PHYS_COPY_CATCH(msg_lin, vir2phys(&dst->p_delivermsg), sizeof(message), addr);
if(addr) {
NOREC_RETURN(queuemess, EFAULT);
}
dst->p_delivermsg.m_source = ep;
dst->p_misc_flags |= MF_DELIVERMSG;
NOREC_RETURN(queuemess, OK);
}
/*===========================================================================*
* schedcheck *
*===========================================================================*/
PUBLIC void schedcheck(void)
{
/* This function is called an instant before proc_ptr is
* to be scheduled again.
*/
NOREC_ENTER(schedch);
vmassert(intr_disabled());
if(next_ptr) {
proc_ptr = next_ptr;
next_ptr = NULL;
}
vmassert(proc_ptr);
vmassert(!proc_ptr->p_rts_flags);
while(proc_ptr->p_misc_flags & MF_DELIVERMSG) {
vmassert(!next_ptr);
vmassert(!proc_ptr->p_rts_flags);
TRACE(VF_SCHEDULING, printf("delivering to %s / %d\n",
proc_ptr->p_name, proc_ptr->p_endpoint););
if(delivermsg(proc_ptr) == VMSUSPEND) {
vmassert(next_ptr);
TRACE(VF_SCHEDULING, printf("suspending %s / %d\n",
proc_ptr->p_name, proc_ptr->p_endpoint););
vmassert(proc_ptr->p_rts_flags);
vmassert(next_ptr != proc_ptr);
proc_ptr = next_ptr;
vmassert(!proc_ptr->p_rts_flags);
next_ptr = NULL;
}
}
TRACE(VF_SCHEDULING, printf("starting %s / %d\n",
proc_ptr->p_name, proc_ptr->p_endpoint););
#if DEBUG_TRACE
proc_ptr->p_schedules++;
#endif
NOREC_RETURN(schedch, );
}
/*===========================================================================*
* 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 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_p; /* Process slot number */
size_t msg_size;
#if DEBUG_SCHED_CHECK
if(caller_ptr->p_misc_flags & MF_DELIVERMSG) {
kprintf("sys_call: MF_DELIVERMSG on for %s / %d\n",
caller_ptr->p_name, caller_ptr->p_endpoint);
minix_panic("MF_DELIVERMSG on", NO_NUM);
}
#endif
#if 0
if(src_dst_e != 4 && src_dst_e != 5 &&
caller_ptr->p_endpoint != 4 && caller_ptr->p_endpoint != 5) {
if(call_nr == SEND)
kprintf("(%d SEND to %d) ", caller_ptr->p_endpoint, src_dst_e);
else if(call_nr == RECEIVE)
kprintf("(%d RECEIVE from %d) ", caller_ptr->p_endpoint, src_dst_e);
else if(call_nr == SENDREC)
kprintf("(%d SENDREC to %d) ", caller_ptr->p_endpoint, src_dst_e);
else
kprintf("(%d %d to/from %d) ", caller_ptr->p_endpoint, call_nr, src_dst_e);
}
#endif
#if DEBUG_SCHED_CHECK
if (RTS_ISSET(caller_ptr, SLOT_FREE))
{
kprintf("called by the dead?!?\n");
return EINVAL;
}
#endif
/* Check destination. SENDA is special because its argument is a table and
* not a single destination. RECEIVE is the only call that accepts ANY (in
* addition to a real endpoint). The other calls (SEND, SENDREC,
* and NOTIFY) require an endpoint to corresponds to a process. In addition,
* it is necessary to check whether a process is allowed to send to a given
* destination.
*/
if (call_nr == SENDA)
{
/* No destination argument */
}
else if (src_dst_e == ANY)
{
if (call_nr != RECEIVE)
{
#if 0
kprintf("sys_call: trap %d by %d with bad endpoint %d\n",
call_nr, proc_nr(caller_ptr), src_dst_e);
#endif
return EINVAL;
}
src_dst_p = src_dst_e;
}
else
{
/* Require a valid source and/or destination process. */
if(!isokendpt(src_dst_e, &src_dst_p)) {
#if 0
kprintf("sys_call: trap %d by %d with bad endpoint %d\n",
call_nr, proc_nr(caller_ptr), src_dst_e);
#endif
return EDEADSRCDST;
}
/* If the call is to send to a process, i.e., for SEND, SENDNB,
* SENDREC or NOTIFY, verify that the caller is allowed to send to
* the given destination.
*/
if (call_nr != RECEIVE)
{
if (!may_send_to(caller_ptr, src_dst_p)) {
#if DEBUG_ENABLE_IPC_WARNINGS
kprintf(
"sys_call: ipc mask denied trap %d from %d to %d\n",
call_nr, caller_ptr->p_endpoint, src_dst_e);
#endif
return(ECALLDENIED); /* call denied by ipc mask */
}
}
}
/* Only allow non-negative call_nr values less than 32 */
if (call_nr < 0 || call_nr >= 32)
{
#if DEBUG_ENABLE_IPC_WARNINGS
kprintf("sys_call: trap %d not allowed, caller %d, src_dst %d\n",
call_nr, proc_nr(caller_ptr), src_dst_p);
#endif
return(ETRAPDENIED); /* trap denied by mask or kernel */
}
/* 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 << call_nr))) {
#if DEBUG_ENABLE_IPC_WARNINGS
kprintf("sys_call: trap %d not allowed, caller %d, src_dst %d\n",
call_nr, proc_nr(caller_ptr), src_dst_p);
#endif
return(ETRAPDENIED); /* trap denied by mask or kernel */
}
if ((iskerneln(src_dst_p) && call_nr != SENDREC && call_nr != RECEIVE)) {
#if DEBUG_ENABLE_IPC_WARNINGS
kprintf("sys_call: trap %d not allowed, caller %d, src_dst %d\n",
call_nr, proc_nr(caller_ptr), src_dst_e);
#endif
return(ETRAPDENIED); /* trap denied by mask or kernel */
}
/* Get and check the size of the argument in bytes.
* Normally this is just the size of a regular message, but in the
* case of SENDA the argument is a table.
*/
if(call_nr == SENDA) {
msg_size = (size_t) src_dst_e;
/* Limit size to something reasonable. An arbitrary choice is 16
* times the number of process table entries.
*/
if (msg_size > 16*(NR_TASKS + NR_PROCS))
return EDOM;
msg_size *= sizeof(asynmsg_t); /* convert to bytes */
} else {
msg_size = sizeof(*m_ptr);
}
/* Check for a possible deadlock for blocking SEND(REC) and RECEIVE. */
if (call_nr == SEND || call_nr == SENDREC || call_nr == RECEIVE) {
if (group_size = deadlock(call_nr, caller_ptr, src_dst_p)) {
#if 0
kprintf("sys_call: trap %d from %d to %d deadlocked, group size %d\n",
call_nr, proc_nr(caller_ptr), src_dst_p, 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: asynchronous call; deliver notification or mark pending
* - SENDA: list of asynchronous send requests
*/
switch(call_nr) {
case SENDREC:
/* A flag is set so that notifications cannot interrupt SENDREC. */
caller_ptr->p_misc_flags |= MF_REPLY_PEND;
/* fall through */
case SEND:
result = mini_send(caller_ptr, src_dst_e, m_ptr, 0);
if (call_nr == SEND || result != OK)
break; /* done, or SEND failed */
/* fall through for SENDREC */
case RECEIVE:
if (call_nr == RECEIVE)
caller_ptr->p_misc_flags &= ~MF_REPLY_PEND;
result = mini_receive(caller_ptr, src_dst_e, m_ptr, 0);
break;
case NOTIFY:
result = mini_notify(caller_ptr, src_dst_e);
break;
case SENDNB:
result = mini_send(caller_ptr, src_dst_e, m_ptr, NON_BLOCKING);
break;
case SENDA:
result = mini_senda(caller_ptr, (asynmsg_t *)m_ptr, (size_t)src_dst_e);
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;
#if DEBUG_ENABLE_IPC_WARNINGS
static struct proc *processes[NR_PROCS + NR_TASKS];
processes[0] = cp;
#endif
while (src_dst != ANY) { /* check while process nr */
int src_dst_e;
xp = proc_addr(src_dst); /* follow chain of processes */
#if DEBUG_ENABLE_IPC_WARNINGS
processes[group_size] = xp;
#endif
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 */
}
}
#if DEBUG_ENABLE_IPC_WARNINGS
{
int i;
kprintf("deadlock between these processes:\n");
for(i = 0; i < group_size; i++) {
kprintf(" %10s ", processes[i]->p_name);
proc_stacktrace(processes[i]);
}
}
#endif
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 */
int 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;
phys_bytes linaddr;
vir_bytes addr;
int r;
if(!(linaddr = umap_local(caller_ptr, D, (vir_bytes) m_ptr,
sizeof(message)))) {
return EFAULT;
}
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 (WILLRECEIVE(dst_ptr, caller_ptr->p_endpoint)) {
/* Destination is indeed waiting for this message. */
vmassert(!(dst_ptr->p_misc_flags & MF_DELIVERMSG));
if((r=QueueMess(caller_ptr->p_endpoint, linaddr, dst_ptr)) != OK)
return r;
RTS_UNSET(dst_ptr, RECEIVING);
} else {
if(flags & NON_BLOCKING) {
return(ENOTREADY);
}
/* Destination is not waiting. Block and dequeue caller. */
PHYS_COPY_CATCH(linaddr, vir2phys(&caller_ptr->p_sendmsg),
sizeof(message), addr);
if(addr) { return EFAULT; }
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 */
}
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 */
int 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.
*/
register struct proc **xpp;
register struct notification **ntf_q_pp;
message m;
int bit_nr;
sys_map_t *map;
bitchunk_t *chunk;
int i, r, src_id, src_proc_nr, src_p;
phys_bytes linaddr;
vmassert(!(caller_ptr->p_misc_flags & MF_DELIVERMSG));
if(!(linaddr = umap_local(caller_ptr, D, (vir_bytes) m_ptr,
sizeof(message)))) {
return EFAULT;
}
/* This is where we want our message. */
caller_ptr->p_delivermsg_lin = linaddr;
caller_ptr->p_delivermsg_vir = (vir_bytes) m_ptr;
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 & MF_REPLY_PEND)) {
map = &priv(caller_ptr)->s_notify_pending;
for (chunk=&map->chunk[0]; chunk<&map->chunk[NR_SYS_CHUNKS]; chunk++) {
endpoint_t hisep;
/* 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. */
BuildNotifyMessage(&m, src_proc_nr, caller_ptr); /* assemble message */
hisep = proc_addr(src_proc_nr)->p_endpoint;
vmassert(!(caller_ptr->p_misc_flags & MF_DELIVERMSG));
vmassert(src_e == ANY || hisep == src_e);
if((r=QueueMess(hisep, vir2phys(&m), caller_ptr)) != OK) {
minix_panic("mini_receive: local QueueMess failed", NO_NUM);
}
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 DEBUG_SCHED_CHECK
if (RTS_ISSET(*xpp, SLOT_FREE) || RTS_ISSET(*xpp, NO_ENDPOINT))
{
kprintf("%d: receive from %d; found dead %d (%s)?\n",
caller_ptr->p_endpoint, src_e, (*xpp)->p_endpoint,
(*xpp)->p_name);
return EINVAL;
}
#endif
/* Found acceptable message. Copy it and update status. */
vmassert(!(caller_ptr->p_misc_flags & MF_DELIVERMSG));
QueueMess((*xpp)->p_endpoint,
vir2phys(&(*xpp)->p_sendmsg), caller_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 */
}
if (caller_ptr->p_misc_flags & MF_ASYNMSG)
{
if (src_e != ANY)
{
#if 0
kprintf("mini_receive: should try async from %d\n", src_e);
#endif
r= EAGAIN;
}
else
{
r= try_async(caller_ptr);
}
if (r == OK)
return OK; /* Got a message */
}
}
/* 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;
RTS_SET(caller_ptr, RECEIVING);
return(OK);
} else {
return(ENOTREADY);
}
}
/*===========================================================================*
* mini_notify *
*===========================================================================*/
PUBLIC int mini_notify(caller_ptr, dst_e)
register struct proc *caller_ptr; /* sender of the notification */
endpoint_t dst_e; /* which process to notify */
{
register struct proc *dst_ptr;
int src_id; /* source id for late delivery */
message m; /* the notification message */
int r;
int proc_nr;
int dst_p;
vmassert(intr_disabled());
if (!isokendpt(dst_e, &dst_p)) {
util_stacktrace();
kprintf("mini_notify: bogus endpoint %d\n", dst_e);
return EDEADSRCDST;
}
dst_ptr = proc_addr(dst_p);
/* 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 (WILLRECEIVE(dst_ptr, caller_ptr->p_endpoint) &&
! (dst_ptr->p_misc_flags & MF_REPLY_PEND)) {
/* 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.
*/
BuildNotifyMessage(&m, proc_nr(caller_ptr), dst_ptr);
vmassert(!(dst_ptr->p_misc_flags & MF_DELIVERMSG));
if((r=QueueMess(caller_ptr->p_endpoint, vir2phys(&m), dst_ptr)) != OK) {
minix_panic("mini_notify: local QueueMess failed", NO_NUM);
}
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);
}
#define ASCOMPLAIN(caller, entry, field) \
kprintf("kernel:%s:%d: asyn failed for %s in %s " \
"(%d/%d, tab 0x%lx)\n",__FILE__,__LINE__, \
field, caller->p_name, entry, priv(caller)->s_asynsize, priv(caller)->s_asyntab)
#define A_RETRIEVE(entry, field) \
if(data_copy(caller_ptr->p_endpoint, \
table_v + (entry)*sizeof(asynmsg_t) + offsetof(struct asynmsg,field),\
SYSTEM, (vir_bytes) &tabent.field, \
sizeof(tabent.field)) != OK) {\
ASCOMPLAIN(caller_ptr, entry, #field); \
return EFAULT; \
}
#define A_INSERT(entry, field) \
if(data_copy(SYSTEM, (vir_bytes) &tabent.field, \
caller_ptr->p_endpoint, \
table_v + (entry)*sizeof(asynmsg_t) + offsetof(struct asynmsg,field),\
sizeof(tabent.field)) != OK) {\
ASCOMPLAIN(caller_ptr, entry, #field); \
return EFAULT; \
}
/*===========================================================================*
* mini_senda *
*===========================================================================*/
PRIVATE int mini_senda(caller_ptr, table, size)
struct proc *caller_ptr;
asynmsg_t *table;
size_t size;
{
int i, dst_p, done, do_notify, r;
unsigned flags;
struct proc *dst_ptr;
struct priv *privp;
message *m_ptr;
asynmsg_t tabent;
vir_bytes table_v = (vir_bytes) table;
vir_bytes linaddr;
privp= priv(caller_ptr);
if (!(privp->s_flags & SYS_PROC))
{
kprintf(
"mini_senda: warning caller has no privilege structure\n");
return EPERM;
}
/* Clear table */
privp->s_asyntab= -1;
privp->s_asynsize= 0;
if (size == 0)
{
/* Nothing to do, just return */
return OK;
}
if(!(linaddr = umap_local(caller_ptr, D, (vir_bytes) table,
size * sizeof(*table)))) {
printf("mini_senda: umap_local failed; 0x%lx len 0x%lx\n",
table, size * sizeof(*table));
return EFAULT;
}
/* Limit size to something reasonable. An arbitrary choice is 16
* times the number of process table entries.
*
* (this check has been duplicated in sys_call but is left here
* as a sanity check)
*/
if (size > 16*(NR_TASKS + NR_PROCS))
{
return EDOM;
}
/* Scan the table */
do_notify= FALSE;
done= TRUE;
for (i= 0; i<size; i++)
{
/* Read status word */
A_RETRIEVE(i, flags);
flags= tabent.flags;
/* Skip empty entries */
if (flags == 0)
continue;
/* Check for reserved bits in the flags field */
if (flags & ~(AMF_VALID|AMF_DONE|AMF_NOTIFY) ||
!(flags & AMF_VALID))
{
return EINVAL;
}
/* Skip entry if AMF_DONE is already set */
if (flags & AMF_DONE)
continue;
/* Get destination */
A_RETRIEVE(i, dst);
if (!isokendpt(tabent.dst, &dst_p))
{
/* Bad destination, report the error */
tabent.result= EDEADSRCDST;
A_INSERT(i, result);
tabent.flags= flags | AMF_DONE;
A_INSERT(i, flags);
if (flags & AMF_NOTIFY)
do_notify= 1;
continue;
}
if (!may_send_to(caller_ptr, dst_p))
{
/* Send denied by IPC mask */
tabent.result= ECALLDENIED;
A_INSERT(i, result);
tabent.flags= flags | AMF_DONE;
A_INSERT(i, flags);
if (flags & AMF_NOTIFY)
do_notify= 1;
continue;
}
#if 0
kprintf("mini_senda: entry[%d]: flags 0x%x dst %d/%d\n",
i, tabent.flags, tabent.dst, dst_p);
#endif
dst_ptr = proc_addr(dst_p);
/* NO_ENDPOINT should be removed */
if (dst_ptr->p_rts_flags & NO_ENDPOINT)
{
tabent.result= EDSTDIED;
A_INSERT(i, result);
tabent.flags= flags | AMF_DONE;
A_INSERT(i, flags);
if (flags & AMF_NOTIFY)
do_notify= TRUE;
continue;
}
/* 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 ( (dst_ptr->p_rts_flags & (RECEIVING | SENDING)) ==
RECEIVING &&
(dst_ptr->p_getfrom_e == ANY ||
dst_ptr->p_getfrom_e == caller_ptr->p_endpoint))
{
/* Destination is indeed waiting for this message. */
m_ptr= &table[i].msg; /* Note: pointer in the
* caller's address space.
*/
/* Copy message from sender. */
tabent.result= QueueMess(caller_ptr->p_endpoint,
linaddr + (vir_bytes) &table[i].msg -
(vir_bytes) table, dst_ptr);
if(tabent.result == OK)
RTS_UNSET(dst_ptr, RECEIVING);
A_INSERT(i, result);
tabent.flags= flags | AMF_DONE;
A_INSERT(i, flags);
if (flags & AMF_NOTIFY)
do_notify= 1;
continue;
}
else
{
/* Should inform receiver that something is pending */
dst_ptr->p_misc_flags |= MF_ASYNMSG;
done= FALSE;
continue;
}
}
if (do_notify)
kprintf("mini_senda: should notify caller\n");
if (!done)
{
privp->s_asyntab= (vir_bytes)table;
privp->s_asynsize= size;
}
return OK;
}
/*===========================================================================*
* try_async *
*===========================================================================*/
PRIVATE int try_async(caller_ptr)
struct proc *caller_ptr;
{
int r;
struct priv *privp;
struct proc *src_ptr;
/* Try all privilege structures */
for (privp = BEG_PRIV_ADDR; privp < END_PRIV_ADDR; ++privp)
{
if (privp->s_proc_nr == NONE || privp->s_id == USER_PRIV_ID)
continue;
if (privp->s_asynsize == 0)
continue;
src_ptr= proc_addr(privp->s_proc_nr);
if (!may_send_to(src_ptr, proc_nr(caller_ptr)))
continue;
vmassert(!(caller_ptr->p_misc_flags & MF_DELIVERMSG));
r= try_one(src_ptr, caller_ptr);
if (r == OK)
return r;
}
/* Nothing found, clear MF_ASYNMSG */
caller_ptr->p_misc_flags &= ~MF_ASYNMSG;
return ESRCH;
}
/*===========================================================================*
* try_one *
*===========================================================================*/
PRIVATE int try_one(src_ptr, dst_ptr)
struct proc *src_ptr;
struct proc *dst_ptr;
{
int i, do_notify, done;
unsigned flags;
size_t size;
endpoint_t dst_e;
asynmsg_t *table_ptr;
message *m_ptr;
struct priv *privp;
asynmsg_t tabent;
vir_bytes table_v;
struct proc *caller_ptr;
int r;
privp= priv(src_ptr);
size= privp->s_asynsize;
table_v = privp->s_asyntab;
caller_ptr = src_ptr;
dst_e= dst_ptr->p_endpoint;
/* Scan the table */
do_notify= FALSE;
done= TRUE;
for (i= 0; i<size; i++)
{
/* Read status word */
A_RETRIEVE(i, flags);
flags= tabent.flags;
/* Skip empty entries */
if (flags == 0)
{
continue;
}
/* Check for reserved bits in the flags field */
if (flags & ~(AMF_VALID|AMF_DONE|AMF_NOTIFY) ||
!(flags & AMF_VALID))
{
kprintf("try_one: bad bits in table\n");
privp->s_asynsize= 0;
return EINVAL;
}
/* Skip entry is AMF_DONE is already set */
if (flags & AMF_DONE)
{
continue;
}
/* Clear done. We are done when all entries are either empty
* or done at the start of the call.
*/
done= FALSE;
/* Get destination */
A_RETRIEVE(i, dst);
if (tabent.dst != dst_e)
{
continue;
}
/* Deliver message */
table_ptr= (asynmsg_t *)privp->s_asyntab;
m_ptr= &table_ptr[i].msg; /* Note: pointer in the
* caller's address space.
*/
A_RETRIEVE(i, msg);
r = QueueMess(src_ptr->p_endpoint, vir2phys(&tabent.msg),
dst_ptr);
tabent.result= r;
A_INSERT(i, result);
tabent.flags= flags | AMF_DONE;
A_INSERT(i, flags);
if (flags & AMF_NOTIFY)
{
kprintf("try_one: should notify caller\n");
}
return OK;
}
if (done)
privp->s_asynsize= 0;
return EAGAIN;
}
/*===========================================================================*
* 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_p;
vmassert(!intr_disabled());
if (!isokendpt(src_e, &src_p)) {
kprintf("lock_notify: bogus src: %d\n", src_e);
return EDEADSRCDST;
}
lock;
vmassert(intr_disabled());
result = mini_notify(proc_addr(src_p), dst_e);
vmassert(intr_disabled());
unlock;
vmassert(!intr_disabled());
return(result);
}
/*===========================================================================*
* enqueue *
*===========================================================================*/
PUBLIC 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 */
NOREC_ENTER(enqueuefunc);
#if DEBUG_SCHED_CHECK
if(!intr_disabled()) { minix_panic("enqueue with interrupts enabled", NO_NUM); }
if (rp->p_ready) minix_panic("enqueue already ready process", NO_NUM);
#endif
/* Determine where to insert to process. */
sched(rp, &q, &front);
vmassert(q >= 0);
vmassert(q < IDLE_Q || rp->p_endpoint == IDLE);
/* 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 */
}
#if DEBUG_SCHED_CHECK
rp->p_ready = 1;
CHECK_RUNQUEUES;
#endif
/* Now select the next process to run, if there isn't a current
* process yet or current process isn't ready any more, or
* it's PREEMPTIBLE.
*/
vmassert(proc_ptr);
if((proc_ptr->p_priority > rp->p_priority) &&
(priv(proc_ptr)->s_flags & PREEMPTIBLE))
pick_proc();
#if DEBUG_SCHED_CHECK
CHECK_RUNQUEUES;
#endif
NOREC_RETURN(enqueuefunc, );
}
/*===========================================================================*
* dequeue *
*===========================================================================*/
PUBLIC 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;
NOREC_ENTER(dequeuefunc);
#if DEBUG_STACK_CHECK
/* Side-effect for kernel: check if the task's stack still is ok? */
if (iskernelp(rp)) {
if (*priv(rp)->s_stack_guard != STACK_GUARD)
minix_panic("stack overrun by task", proc_nr(rp));
}
#endif
#if DEBUG_SCHED_CHECK
if(!intr_disabled()) { minix_panic("dequeue with interrupts enabled", NO_NUM); }
if (! rp->p_ready) minix_panic("dequeue() already unready process", NO_NUM);
#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 DEBUG_SCHED_CHECK
rp->p_ready = 0;
CHECK_RUNQUEUES;
#endif
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
CHECK_RUNQUEUES;
#endif
NOREC_RETURN(dequeuefunc, );
}
/*===========================================================================*
* 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 */
NOREC_ENTER(pick);
/* 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++) {
int found = 0;
if(!(rp = rdy_head[q])) {
TRACE(VF_PICKPROC, printf("queue %d empty\n", q););
continue;
}
TRACE(VF_PICKPROC, printf("found %s / %d on queue %d\n",
rp->p_name, rp->p_endpoint, q););
next_ptr = rp; /* run process 'rp' next */
vmassert(proc_ptr != next_ptr);
vmassert(!next_ptr->p_rts_flags);
if (priv(rp)->s_flags & BILLABLE)
bill_ptr = rp; /* bill for system time */
NOREC_RETURN(pick, );
}
}
/*===========================================================================*
* 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 */
vmassert(!intr_disabled());
lock;
for (rp=BEG_PROC_ADDR; rp<END_PROC_ADDR; rp++) {
if (! isemptyp(rp)) { /* check slot use */
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;
/* 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;
result = mini_send(proc_ptr, dst_e, m_ptr, 0);
unlock;
return(result);
}
/*===========================================================================*
* endpoint_lookup *
*===========================================================================*/
PUBLIC struct proc *endpoint_lookup(endpoint_t e)
{
int n;
if(!isokendpt(e, &n)) return NULL;
return proc_addr(n);
}
/*===========================================================================*
* 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 0
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) {
minix_panic("invalid endpoint ", e);
}
return ok;
}
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