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minix/kernel/proc.c
Tomas Hruby 76708e9bf4 mini_receive() clean up 
- for better readability xpp is substitued by sender

- makes sure that the dequeued sender has p_q_link == NULL and that
  this condition holds when enqueuing the sender again. This is a
  sanity check to make sure that the new sender is not enqueued
  already

- Before this change the dequeued sender's p_q_link may not be NULL
  and it was only set to NULL when enqueued again
2010-06-23 10:36:19 +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
*
* 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/endpoint.h>
#include <stddef.h>
#include <signal.h>
#include <minix/syslib.h>
#include <assert.h>
#include "debug.h"
#include "kernel.h"
#include "proc.h"
#include "vm.h"
#include "clock.h"
/* Scheduling and message passing functions */
FORWARD _PROTOTYPE( void idle, (void));
/**
* Made public for use in clock.c (for user-space scheduling)
FORWARD _PROTOTYPE( int mini_send, (struct proc *caller_ptr, endpoint_t dst_e,
message *m_ptr, int flags));
*/
FORWARD _PROTOTYPE( int mini_receive, (struct proc *caller_ptr, endpoint_t 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, proc_nr_t src_dst));
FORWARD _PROTOTYPE( int try_async, (struct proc *caller_ptr));
FORWARD _PROTOTYPE( int try_one, (struct proc *src_ptr, struct proc *dst_ptr,
int *postponed));
FORWARD _PROTOTYPE( struct proc * pick_proc, (void));
FORWARD _PROTOTYPE( void enqueue_head, (struct proc *rp));
#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; \
}
/*===========================================================================*
* idle *
*===========================================================================*/
PRIVATE void idle(void)
{
/* This function is called whenever there is no work to do.
* Halt the CPU, and measure how many timestamp counter ticks are
* spent not doing anything. This allows test setups to measure
* the CPU utiliziation of certain workloads with high precision.
*/
/* start accounting for the idle time */
context_stop(proc_addr(KERNEL));
halt_cpu();
/*
* end of accounting for the idle task does not happen here, the kernel
* is handling stuff for quite a while before it gets back here!
*/
}
/*===========================================================================*
* switch_to_user *
*===========================================================================*/
PUBLIC void switch_to_user(void)
{
/* This function is called an instant before proc_ptr is
* to be scheduled again.
*/
/*
* if the current process is still runnable check the misc flags and let
* it run unless it becomes not runnable in the meantime
*/
if (proc_is_runnable(proc_ptr))
goto check_misc_flags;
/*
* if a process becomes not runnable while handling the misc flags, we
* need to pick a new one here and start from scratch. Also if the
* current process wasn' runnable, we pick a new one here
*/
not_runnable_pick_new:
if (proc_is_preempted(proc_ptr)) {
proc_ptr->p_rts_flags &= ~RTS_PREEMPTED;
if (proc_is_runnable(proc_ptr)) {
if (!is_zero64(proc_ptr->p_cpu_time_left))
enqueue_head(proc_ptr);
else
enqueue(proc_ptr);
}
}
/*
* if we have no process to run, set IDLE as the current process for
* time accounting and put the cpu in and idle state. After the next
* timer interrupt the execution resumes here and we can pick another
* process. If there is still nothing runnable we "schedule" IDLE again
*/
while (!(proc_ptr = pick_proc())) {
proc_ptr = proc_addr(IDLE);
if (priv(proc_ptr)->s_flags & BILLABLE)
bill_ptr = proc_ptr;
idle();
}
switch_address_space(proc_ptr);
check_misc_flags:
assert(proc_ptr);
assert(proc_is_runnable(proc_ptr));
while (proc_ptr->p_misc_flags &
(MF_KCALL_RESUME | MF_DELIVERMSG |
MF_SC_DEFER | MF_SC_TRACE | MF_SC_ACTIVE)) {
assert(proc_is_runnable(proc_ptr));
if (proc_ptr->p_misc_flags & MF_KCALL_RESUME) {
kernel_call_resume(proc_ptr);
}
else if (proc_ptr->p_misc_flags & MF_DELIVERMSG) {
TRACE(VF_SCHEDULING, printf("delivering to %s / %d\n",
proc_ptr->p_name, proc_ptr->p_endpoint););
delivermsg(proc_ptr);
}
else if (proc_ptr->p_misc_flags & MF_SC_DEFER) {
/* Perform the system call that we deferred earlier. */
assert (!(proc_ptr->p_misc_flags & MF_SC_ACTIVE));
arch_do_syscall(proc_ptr);
/* If the process is stopped for signal delivery, and
* not blocked sending a message after the system call,
* inform PM.
*/
if ((proc_ptr->p_misc_flags & MF_SIG_DELAY) &&
!RTS_ISSET(proc_ptr, RTS_SENDING))
sig_delay_done(proc_ptr);
}
else if (proc_ptr->p_misc_flags & MF_SC_TRACE) {
/* Trigger a system call leave event if this was a
* system call. We must do this after processing the
* other flags above, both for tracing correctness and
* to be able to use 'break'.
*/
if (!(proc_ptr->p_misc_flags & MF_SC_ACTIVE))
break;
proc_ptr->p_misc_flags &=
~(MF_SC_TRACE | MF_SC_ACTIVE);
/* Signal the "leave system call" event.
* Block the process.
*/
cause_sig(proc_nr(proc_ptr), SIGTRAP);
}
else if (proc_ptr->p_misc_flags & MF_SC_ACTIVE) {
/* If MF_SC_ACTIVE was set, remove it now:
* we're leaving the system call.
*/
proc_ptr->p_misc_flags &= ~MF_SC_ACTIVE;
break;
}
if (!proc_is_runnable(proc_ptr))
break;
}
/*
* check the quantum left before it runs again. We must do it only here
* as we are sure that a possible out-of-quantum message to the
* scheduler will not collide with the regular ipc
*/
if (is_zero64(proc_ptr->p_cpu_time_left))
proc_no_time(proc_ptr);
/*
* After handling the misc flags the selected process might not be
* runnable anymore. We have to checkit and schedule another one
*/
if (!proc_is_runnable(proc_ptr))
goto not_runnable_pick_new;
TRACE(VF_SCHEDULING, printf("starting %s / %d\n",
proc_ptr->p_name, proc_ptr->p_endpoint););
#if DEBUG_TRACE
proc_ptr->p_schedules++;
#endif
proc_ptr = arch_finish_switch_to_user();
assert(!is_zero64(proc_ptr->p_cpu_time_left));
context_stop(proc_addr(KERNEL));
/* If the process isn't the owner of FPU, enable the FPU exception */
if(fpu_owner != proc_ptr)
enable_fpu_exception();
else
disable_fpu_exception();
/*
* restore_user_context() carries out the actual mode switch from kernel
* to userspace. This function does not return
*/
restore_user_context(proc_ptr);
NOT_REACHABLE;
}
/*
* handler for all synchronous IPC calls
*/
PRIVATE int do_sync_ipc(struct proc * caller_ptr, /* who made the call */
int call_nr, /* system call number and flags */
endpoint_t src_dst_e, /* src or dst of the call */
message *m_ptr) /* users pointer to a message */
{
int result; /* the system call's result */
int src_dst_p; /* Process slot number */
/* Check 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.
*/
assert(call_nr != SENDA);
if (src_dst_e == ANY)
{
if (call_nr != RECEIVE)
{
#if 0
printf("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 = (int) src_dst_e;
}
else
{
/* Require a valid source and/or destination process. */
if(!isokendpt(src_dst_e, &src_dst_p)) {
#if 0
printf("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
printf(
"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
printf("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
printf("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 (call_nr != SENDREC && call_nr != RECEIVE && iskerneln(src_dst_p)) {
#if DEBUG_ENABLE_IPC_WARNINGS
printf("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 */
}
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;
IPC_STATUS_CLEAR(caller_ptr); /* clear IPC status code */
}
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;
default:
result = EBADCALL; /* illegal system call */
}
/* Now, return the result of the system call to the caller. */
return(result);
}
PUBLIC int do_ipc(reg_t r1, reg_t r2, reg_t r3)
{
struct proc * caller_ptr = proc_ptr; /* always the current process */
int call_nr = (int) r1;
assert(!RTS_ISSET(caller_ptr, RTS_SLOT_FREE));
/* If this process is subject to system call tracing, handle that first. */
if (caller_ptr->p_misc_flags & (MF_SC_TRACE | MF_SC_DEFER)) {
/* Are we tracing this process, and is it the first sys_call entry? */
if ((caller_ptr->p_misc_flags & (MF_SC_TRACE | MF_SC_DEFER)) ==
MF_SC_TRACE) {
/* We must notify the tracer before processing the actual
* system call. If we don't, the tracer could not obtain the
* input message. Postpone the entire system call.
*/
caller_ptr->p_misc_flags &= ~MF_SC_TRACE;
caller_ptr->p_misc_flags |= MF_SC_DEFER;
/* Signal the "enter system call" event. Block the process. */
cause_sig(proc_nr(caller_ptr), SIGTRAP);
/* Preserve the return register's value. */
return caller_ptr->p_reg.retreg;
}
/* If the MF_SC_DEFER flag is set, the syscall is now being resumed. */
caller_ptr->p_misc_flags &= ~MF_SC_DEFER;
assert (!(caller_ptr->p_misc_flags & MF_SC_ACTIVE));
/* Set a flag to allow reliable tracing of leaving the system call. */
caller_ptr->p_misc_flags |= MF_SC_ACTIVE;
}
if(caller_ptr->p_misc_flags & MF_DELIVERMSG) {
panic("sys_call: MF_DELIVERMSG on for %s / %d\n",
caller_ptr->p_name, caller_ptr->p_endpoint);
}
/* 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:
case SEND:
case RECEIVE:
case NOTIFY:
case SENDNB:
return do_sync_ipc(caller_ptr, call_nr, (endpoint_t) r2,
(message *) r3);
case SENDA:
{
/*
* Get and check the size of the argument in bytes as it is a
* table
*/
size_t msg_size = (size_t) r2;
/* 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;
return mini_senda(caller_ptr, (asynmsg_t *) r3, msg_size);
}
default:
return EBADCALL; /* illegal system call */
}
}
/*===========================================================================*
* deadlock *
*===========================================================================*/
PRIVATE int deadlock(function, cp, src_dst)
int function; /* trap number */
register struct proc *cp; /* pointer to caller */
proc_nr_t 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 */
#if DEBUG_ENABLE_IPC_WARNINGS
static struct proc *processes[NR_PROCS + NR_TASKS];
processes[0] = cp;
#endif
/* FIXME: this compares a proc_nr_t with a endpoint_t */
while (src_dst != ANY) { /* check while process nr */
endpoint_t dep;
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((dep = P_BLOCKEDON(xp)) == NONE)
return 0;
if(dep == ANY)
/* FIXME: this assigns a proc_nr_t to a endpoint_t */
src_dst = ANY;
else
okendpt(dep, &src_dst);
/* 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)) & RTS_SENDING) {
return(0); /* not a deadlock */
}
}
#if DEBUG_ENABLE_IPC_WARNINGS
{
int i;
printf("deadlock between these processes:\n");
for(i = 0; i < group_size; i++) {
printf(" %10s ", processes[i]->p_name);
}
printf("\n\n");
for(i = 0; i < group_size; i++) {
print_proc(processes[i]);
proc_stacktrace(processes[i]);
}
}
#endif
return(group_size); /* deadlock found */
}
}
return(0); /* not a deadlock */
}
/*===========================================================================*
* mini_send *
*===========================================================================*/
PUBLIC int mini_send(
register struct proc *caller_ptr, /* who is trying to send a message? */
endpoint_t dst_e, /* to whom is message being sent? */
message *m_ptr, /* pointer to message buffer */
const 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;
dst_p = _ENDPOINT_P(dst_e);
dst_ptr = proc_addr(dst_p);
if (RTS_ISSET(dst_ptr, RTS_NO_ENDPOINT))
{
return EDEADSRCDST;
}
/* Check if 'dst' is blocked waiting for this message. The destination's
* RTS_SENDING flag may be set when its SENDREC call blocked while sending.
*/
if (WILLRECEIVE(dst_ptr, caller_ptr->p_endpoint)) {
int call;
/* Destination is indeed waiting for this message. */
assert(!(dst_ptr->p_misc_flags & MF_DELIVERMSG));
if (!(flags & FROM_KERNEL)) {
if(copy_msg_from_user(caller_ptr, m_ptr, &dst_ptr->p_delivermsg))
return EFAULT;
} else {
dst_ptr->p_delivermsg = *m_ptr;
IPC_STATUS_ADD_FLAGS(dst_ptr, IPC_FLG_MSG_FROM_KERNEL);
}
dst_ptr->p_delivermsg.m_source = caller_ptr->p_endpoint;
dst_ptr->p_misc_flags |= MF_DELIVERMSG;
call = (caller_ptr->p_misc_flags & MF_REPLY_PEND ? SENDREC
: (flags & NON_BLOCKING ? SENDNB : SEND));
IPC_STATUS_ADD_CALL(dst_ptr, call);
RTS_UNSET(dst_ptr, RTS_RECEIVING);
} else {
if(flags & NON_BLOCKING) {
return(ENOTREADY);
}
/* Check for a possible deadlock before actually blocking. */
if (deadlock(SEND, caller_ptr, dst_p)) {
return(ELOCKED);
}
/* Destination is not waiting. Block and dequeue caller. */
if (!(flags & FROM_KERNEL)) {
if(copy_msg_from_user(caller_ptr, m_ptr, &caller_ptr->p_sendmsg))
return EFAULT;
} else {
caller_ptr->p_sendmsg = *m_ptr;
/*
* we need to remember that this message is from kernel so we
* can set the delivery status flags when the message is
* actually delivered
*/
caller_ptr->p_misc_flags |= MF_SENDING_FROM_KERNEL;
}
RTS_SET(caller_ptr, RTS_SENDING);
caller_ptr->p_sendto_e = dst_e;
/* Process is now blocked. Put in on the destination's queue. */
assert(caller_ptr->p_q_link == NULL);
xpp = &dst_ptr->p_caller_q; /* find end of list */
while (*xpp) xpp = &(*xpp)->p_q_link;
*xpp = caller_ptr; /* add caller to end */
}
return(OK);
}
/*===========================================================================*
* mini_receive *
*===========================================================================*/
PRIVATE int mini_receive(struct proc * caller_ptr,
int src_e, /* which message source is wanted */
message * m_buff_usr, /* pointer to message buffer */
const 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;
sys_map_t *map;
bitchunk_t *chunk;
int i, r, src_id, src_proc_nr, src_p;
assert(!(caller_ptr->p_misc_flags & MF_DELIVERMSG));
/* This is where we want our message. */
caller_ptr->p_delivermsg_vir = (vir_bytes) m_buff_usr;
if(src_e == ANY) src_p = ANY;
else
{
okendpt(src_e, &src_p);
if (RTS_ISSET(proc_addr(src_p), RTS_NO_ENDPOINT))
{
return EDEADSRCDST;
}
}
/* Check to see if a message from desired source is already available. The
* caller's RTS_SENDING flag may be set if SENDREC couldn't send. If it is
* set, the process should be blocked.
*/
if (!RTS_ISSET(caller_ptr, RTS_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) {
printf("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. */
hisep = proc_addr(src_proc_nr)->p_endpoint;
assert(!(caller_ptr->p_misc_flags & MF_DELIVERMSG));
assert(src_e == ANY || hisep == src_e);
/* assemble message */
BuildNotifyMessage(&caller_ptr->p_delivermsg, src_proc_nr, caller_ptr);
caller_ptr->p_delivermsg.m_source = hisep;
caller_ptr->p_misc_flags |= MF_DELIVERMSG;
IPC_STATUS_ADD_CALL(caller_ptr, NOTIFY);
return(OK);
}
}
/* Check if there are pending senda(). */
if (caller_ptr->p_misc_flags & MF_ASYNMSG)
{
if (src_e != ANY)
r= try_one(proc_addr(src_p), caller_ptr, NULL);
else
r= try_async(caller_ptr);
if (r == OK) {
IPC_STATUS_ADD_CALL(caller_ptr, SENDA);
return OK; /* Got a message */
}
}
/* Check caller queue. Use pointer pointers to keep code simple. */
xpp = &caller_ptr->p_caller_q;
while (*xpp) {
struct proc * sender = *xpp;
if (src_e == ANY || src_p == proc_nr(sender)) {
int call;
assert(!RTS_ISSET(sender, RTS_SLOT_FREE));
assert(!RTS_ISSET(sender, RTS_NO_ENDPOINT));
/* Found acceptable message. Copy it and update status. */
assert(!(caller_ptr->p_misc_flags & MF_DELIVERMSG));
caller_ptr->p_delivermsg = sender->p_sendmsg;
caller_ptr->p_delivermsg.m_source = sender->p_endpoint;
caller_ptr->p_misc_flags |= MF_DELIVERMSG;
RTS_UNSET(sender, RTS_SENDING);
call = (sender->p_misc_flags & MF_REPLY_PEND ? SENDREC : SEND);
IPC_STATUS_ADD_CALL(caller_ptr, call);
/*
* if the message is originaly from the kernel on behalf of this
* process, we must send the status flags accordingly
*/
if (sender->p_misc_flags & MF_SENDING_FROM_KERNEL) {
IPC_STATUS_ADD_FLAGS(caller_ptr, IPC_FLG_MSG_FROM_KERNEL);
/* we can clean the flag now, not need anymore */
sender->p_misc_flags &= ~MF_SENDING_FROM_KERNEL;
}
if (sender->p_misc_flags & MF_SIG_DELAY)
sig_delay_done(sender);
*xpp = sender->p_q_link; /* remove from queue */
sender->p_q_link = NULL;
return(OK); /* report success */
}
xpp = &sender->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)) {
/* Check for a possible deadlock before actually blocking. */
if (deadlock(RECEIVE, caller_ptr, src_p)) {
return(ELOCKED);
}
caller_ptr->p_getfrom_e = src_e;
RTS_SET(caller_ptr, RTS_RECEIVING);
return(OK);
} else {
return(ENOTREADY);
}
}
/*===========================================================================*
* mini_notify *
*===========================================================================*/
PUBLIC int mini_notify(
const 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 */
int dst_p;
if (!isokendpt(dst_e, &dst_p)) {
util_stacktrace();
printf("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.
*/
assert(!(dst_ptr->p_misc_flags & MF_DELIVERMSG));
BuildNotifyMessage(&dst_ptr->p_delivermsg, proc_nr(caller_ptr), dst_ptr);
dst_ptr->p_delivermsg.m_source = caller_ptr->p_endpoint;
dst_ptr->p_misc_flags |= MF_DELIVERMSG;
IPC_STATUS_ADD_CALL(dst_ptr, NOTIFY);
RTS_UNSET(dst_ptr, RTS_RECEIVING);
return(OK);
}
/* Destination is not ready to receive the notification. Add it to the
* bit map with pending notifications. Note the indirectness: the privilege 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) \
printf("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),\
KERNEL, (vir_bytes) &tabent.field, \
sizeof(tabent.field)) != OK) {\
ASCOMPLAIN(caller_ptr, entry, #field); \
return EFAULT; \
}
#define A_INSERT(entry, field) \
if(data_copy(KERNEL, (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(struct proc *caller_ptr, asynmsg_t *table, size_t size)
{
int i, dst_p, done, do_notify;
unsigned flags;
struct proc *dst_ptr;
struct priv *privp;
asynmsg_t tabent;
const vir_bytes table_v = (vir_bytes) table;
privp= priv(caller_ptr);
if (!(privp->s_flags & SYS_PROC))
{
printf(
"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;
}
/* 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|AMF_NOREPLY) ||
!(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 (iskerneln(dst_p))
{
/* Asynchronous sends to the kernel are not allowed */
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 (!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
printf("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);
/* RTS_NO_ENDPOINT should be removed */
if (RTS_ISSET(dst_ptr, RTS_NO_ENDPOINT))
{
tabent.result= EDEADSRCDST;
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.
* If AMF_NOREPLY is set, do not satisfy the receiving part of
* a SENDREC.
*/
if (WILLRECEIVE(dst_ptr, caller_ptr->p_endpoint) &&
(!(flags & AMF_NOREPLY) ||
!(dst_ptr->p_misc_flags & MF_REPLY_PEND)))
{
/* Destination is indeed waiting for this message. */
/* Copy message from sender. */
if(copy_msg_from_user(caller_ptr, &table[i].msg,
&dst_ptr->p_delivermsg))
tabent.result = EFAULT;
else {
dst_ptr->p_delivermsg.m_source = caller_ptr->p_endpoint;
dst_ptr->p_misc_flags |= MF_DELIVERMSG;
IPC_STATUS_ADD_CALL(dst_ptr, SENDA);
RTS_UNSET(dst_ptr, RTS_RECEIVING);
tabent.result = OK;
}
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)
printf("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;
int postponed = FALSE;
/* Try all privilege structures */
for (privp = BEG_PRIV_ADDR; privp < END_PRIV_ADDR; ++privp)
{
if (privp->s_proc_nr == NONE)
continue;
src_ptr= proc_addr(privp->s_proc_nr);
assert(!(caller_ptr->p_misc_flags & MF_DELIVERMSG));
r= try_one(src_ptr, caller_ptr, &postponed);
if (r == OK)
return r;
}
/* Nothing found, clear MF_ASYNMSG unless messages were postponed */
if (postponed == FALSE)
caller_ptr->p_misc_flags &= ~MF_ASYNMSG;
return ESRCH;
}
/*===========================================================================*
* try_one *
*===========================================================================*/
PRIVATE int try_one(struct proc *src_ptr, struct proc *dst_ptr, int *postponed)
{
int i, done;
unsigned flags;
size_t size;
endpoint_t dst_e;
struct priv *privp;
asynmsg_t tabent;
vir_bytes table_v;
struct proc *caller_ptr;
privp= priv(src_ptr);
/* Basic validity checks */
if (privp->s_id == USER_PRIV_ID) return EAGAIN;
if (privp->s_asynsize == 0) return EAGAIN;
if (!may_send_to(src_ptr, proc_nr(dst_ptr))) return EAGAIN;
size= privp->s_asynsize;
table_v = privp->s_asyntab;
caller_ptr = src_ptr;
dst_e= dst_ptr->p_endpoint;
/* Scan the table */
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|AMF_NOREPLY) ||
!(flags & AMF_VALID))
{
printf("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;
}
/* If AMF_NOREPLY is set, do not satisfy the receiving part of
* a SENDREC. Do not unset MF_ASYNMSG later because of this,
* though: this message is still to be delivered later.
*/
if ((flags & AMF_NOREPLY) &&
(dst_ptr->p_misc_flags & MF_REPLY_PEND))
{
if (postponed != NULL)
*postponed = TRUE;
continue;
}
/* Deliver message */
A_RETRIEVE(i, msg);
dst_ptr->p_delivermsg = tabent.msg;
dst_ptr->p_delivermsg.m_source = src_ptr->p_endpoint;
dst_ptr->p_misc_flags |= MF_DELIVERMSG;
tabent.result = OK;
A_INSERT(i, result);
tabent.flags= flags | AMF_DONE;
A_INSERT(i, flags);
if (flags & AMF_NOTIFY)
{
printf("try_one: should notify caller\n");
}
return OK;
}
if (done)
privp->s_asynsize= 0;
return EAGAIN;
}
/*===========================================================================*
* enqueue *
*===========================================================================*/
PUBLIC void enqueue(
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 = rp->p_priority; /* scheduling queue to use */
#if DEBUG_RACE
/* With DEBUG_RACE, schedule everyone at the same priority level. */
rp->p_priority = q = MIN_USER_Q;
#endif
assert(proc_is_runnable(rp));
assert(q >= 0);
/* Now add the process to the queue. */
if (!rdy_head[q]) { /* add to empty queue */
rdy_head[q] = rdy_tail[q] = rp; /* create a new queue */
rp->p_nextready = NULL; /* mark new end */
}
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 = NULL; /* mark new end */
}
/*
* enqueueing a process with a higher priority than the current one, it gets
* preempted. The current process must be preemptible. Testing the priority
* also makes sure that a process does not preempt itself
*/
assert(proc_ptr && proc_ptr_ok(proc_ptr));
if ((proc_ptr->p_priority > rp->p_priority) &&
(priv(proc_ptr)->s_flags & PREEMPTIBLE))
RTS_SET(proc_ptr, RTS_PREEMPTED); /* calls dequeue() */
#if DEBUG_SANITYCHECKS
assert(runqueues_ok());
#endif
}
/*===========================================================================*
* enqueue_head *
*===========================================================================*/
/*
* put a process at the front of its run queue. It comes handy when a process is
* preempted and removed from run queue to not to have a currently not-runnable
* process on a run queue. We have to put this process back at the fron to be
* fair
*/
PRIVATE void enqueue_head(struct proc *rp)
{
const int q = rp->p_priority; /* scheduling queue to use */
assert(proc_ptr_ok(rp));
assert(proc_is_runnable(rp));
/*
* the process was runnable without its quantum expired when dequeued. A
* process with no time left should vahe been handled else and differently
*/
assert(!is_zero64(rp->p_cpu_time_left));
assert(q >= 0);
/* Now add the process to the queue. */
if (!rdy_head[q]) { /* add to empty queue */
rdy_head[q] = rdy_tail[q] = rp; /* create a new queue */
rp->p_nextready = NULL; /* mark new end */
}
else /* add to head of queue */
rp->p_nextready = rdy_head[q]; /* chain head of queue */
rdy_head[q] = rp; /* set new queue head */
#if DEBUG_SANITYCHECKS
assert(runqueues_ok());
#endif
}
/*===========================================================================*
* dequeue *
*===========================================================================*/
PUBLIC void dequeue(const 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;
assert(proc_ptr_ok(rp));
assert(!proc_is_runnable(rp));
/* Side-effect for kernel: check if the task's stack still is ok? */
assert (!iskernelp(rp) || *priv(rp)->s_stack_guard == STACK_GUARD);
/* 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 = NULL;
for (xpp = &rdy_head[q]; *xpp; 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 */
}
break;
}
prev_xp = *xpp; /* save previous in chain */
}
#if DEBUG_SANITYCHECKS
assert(runqueues_ok());
#endif
}
#if DEBUG_RACE
/*===========================================================================*
* random_process *
*===========================================================================*/
PRIVATE struct proc *random_process(struct proc *head)
{
int i, n = 0;
struct proc *rp;
u64_t r;
read_tsc_64(&r);
for(rp = head; rp; rp = rp->p_nextready)
n++;
/* Use low-order word of TSC as pseudorandom value. */
i = r.lo % n;
for(rp = head; i--; rp = rp->p_nextready)
;
assert(rp);
return rp;
}
#endif
/*===========================================================================*
* pick_proc *
*===========================================================================*/
PRIVATE struct proc * pick_proc(void)
{
/* Decide who to run now. A new process is selected an returned.
* 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])) {
TRACE(VF_PICKPROC, printf("queue %d empty\n", q););
continue;
}
#if DEBUG_RACE
rp = random_process(rdy_head[q]);
#endif
TRACE(VF_PICKPROC, printf("found %s / %d on queue %d\n",
rp->p_name, rp->p_endpoint, q););
assert(proc_is_runnable(rp));
if (priv(rp)->s_flags & BILLABLE)
bill_ptr = rp; /* bill for system time */
return rp;
}
return NULL;
}
/*===========================================================================*
* 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)
const char *file;
int line;
#else
PUBLIC int isokendpt_f(e, p, fatalflag)
#endif
endpoint_t e;
int *p;
const int 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
printf("kernel:%s:%d: bad endpoint %d: proc %d out of range\n",
file, line, e, *p);
#endif
} else if(isemptyn(*p)) {
#if 0
printf("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
printf("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: %d", e);
}
return ok;
}
PRIVATE void notify_scheduler(struct proc *p)
{
message m_no_quantum;
int err;
assert(!proc_kernel_scheduler(p));
/* dequeue the process */
RTS_SET(p, RTS_NO_QUANTUM);
/*
* Notify the process's scheduler that it has run out of
* quantum. This is done by sending a message to the scheduler
* on the process's behalf
*/
m_no_quantum.m_source = p->p_endpoint;
m_no_quantum.m_type = SCHEDULING_NO_QUANTUM;
if ((err = mini_send(p, p->p_scheduler->p_endpoint,
&m_no_quantum, FROM_KERNEL))) {
panic("WARNING: Scheduling: mini_send returned %d\n", err);
}
}
PUBLIC void proc_no_time(struct proc * p)
{
if (!proc_kernel_scheduler(p) && priv(p)->s_flags & PREEMPTIBLE) {
/* this dequeues the process */
notify_scheduler(p);
}
else {
/*
* non-preemptible processes only need their quantum to
* be renewed. In fact, they by pass scheduling
*/
p->p_cpu_time_left = ms_2_cpu_time(p->p_quantum_size_ms);
#if DEBUG_RACE
RTS_SET(proc_ptr, RTS_PREEMPTED);
RTS_UNSET(proc_ptr, RTS_PREEMPTED);
#endif
}
}
PUBLIC void copr_not_available_handler(void)
{
/*
* Disable the FPU exception (both for the kernel and for the process
* once it's scheduled), and initialize or restore the FPU state.
*/
disable_fpu_exception();
/* if FPU is not owned by anyone, do not store anything */
if (fpu_owner != NULL) {
assert(fpu_owner != proc_ptr);
save_fpu(fpu_owner);
}
/*
* restore the current process' state and let it run again, do not
* schedule!
*/
restore_fpu(proc_ptr);
fpu_owner = proc_ptr;
context_stop(proc_addr(KERNEL));
restore_user_context(proc_ptr);
NOT_REACHABLE;
}
PUBLIC void release_fpu(void) {
fpu_owner = NULL;
}
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