/* 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 #include #include #include #include #include #include "debug.h" #include "kernel.h" #include "proc.h" #include "vm.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, 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, 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 */ cycles_accounting_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! */ } /*===========================================================================* * schedcheck * *===========================================================================*/ PUBLIC struct proc * schedcheck(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)) enqueue_head(proc_ptr); } /* * If this process is scheduled by the kernel, we renew it's quantum * and remove it's RTS_NO_QUANTUM flag. */ if (proc_no_quantum(proc_ptr) && proc_kernel_scheduler(proc_ptr)) { /* give new quantum */ proc_ptr->p_ticks_left = proc_ptr->p_quantum_size; RTS_UNSET(proc_ptr, RTS_NO_QUANTUM); } /* * 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)); assert(proc_ptr->p_ticks_left > 0); 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);); if(delivermsg(proc_ptr) == VMSUSPEND) { TRACE(VF_SCHEDULING, printf("suspending %s / %d\n", proc_ptr->p_name, proc_ptr->p_endpoint);); assert(!proc_is_runnable(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; } /* * 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_schedcheck(); assert(proc_ptr->p_ticks_left > 0); cycles_accounting_stop(proc_addr(KERNEL)); return proc_ptr; } /* * 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 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) 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(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 */ 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. */ xpp = &dst_ptr->p_caller_q; /* find end of list */ while (*xpp) xpp = &(*xpp)->p_q_link; *xpp = caller_ptr; /* add caller to end */ caller_ptr->p_q_link = NULL; /* 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 */ 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; phys_bytes linaddr; assert(!(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), 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<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) { if (src_e == ANY || src_p == proc_nr(*xpp)) { int call; assert(!RTS_ISSET(*xpp, RTS_SLOT_FREE)); assert(!RTS_ISSET(*xpp, RTS_NO_ENDPOINT)); /* Found acceptable message. Copy it and update status. */ assert(!(caller_ptr->p_misc_flags & MF_DELIVERMSG)); caller_ptr->p_delivermsg = (*xpp)->p_sendmsg; caller_ptr->p_delivermsg.m_source = (*xpp)->p_endpoint; caller_ptr->p_misc_flags |= MF_DELIVERMSG; RTS_UNSET(*xpp, RTS_SENDING); call = ((*xpp)->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 ((*xpp)->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 */ (*xpp)->p_misc_flags &= ~MF_SENDING_FROM_KERNEL; } if ((*xpp)->p_misc_flags & MF_SIG_DELAY) sig_delay_done(*xpp); *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)) { /* 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; ip_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; is_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 */ 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(rp->p_ticks_left > 0); 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 } /*===========================================================================* * 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; } 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) { /* 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 */ if (proc_kernel_scheduler(p)) { /* * If a scheduler is scheduling itself or has no scheduler, and * runs out of quantum, we don't send a message. The * RTS_NO_QUANTUM flag will be removed by schedcheck in proc.c. */ } else { message m_no_quantum; int err; 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 check_ticks_left(struct proc * p) { if (p->p_ticks_left <= 0) { p->p_ticks_left = 0; if (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_ticks_left = p->p_quantum_size; } } }