/* 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 #include #include #include #include #include #include #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, int *postponed)); FORWARD _PROTOTYPE( void sched, (struct proc *rp, int *queue, int *front)); 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; \ } /*===========================================================================* * 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); } } } #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 struct proc * schedcheck(void) { /* This function is called an instant before proc_ptr is * to be scheduled again. */ NOREC_ENTER(schedch); vmassert(intr_disabled()); /* * 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); } /* this enqueues the process again */ if (proc_no_quantum(proc_ptr)) 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; halt_cpu(); } check_misc_flags: vmassert(proc_ptr); vmassert(proc_is_runnable(proc_ptr)); while (proc_ptr->p_misc_flags & (MF_DELIVERMSG | MF_SC_DEFER | MF_SC_TRACE | MF_SC_ACTIVE)) { vmassert(proc_is_runnable(proc_ptr)); 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);); vmassert(!proc_is_runnable(proc_ptr)); } } else if (proc_ptr->p_misc_flags & MF_SC_DEFER) { /* Perform the system call that we deferred earlier. */ #if DEBUG_SCHED_CHECK if (proc_ptr->p_misc_flags & MF_SC_ACTIVE) minix_panic("MF_SC_ACTIVE and MF_SC_DEFER set", NO_NUM); #endif 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; } /* * 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(); NOREC_RETURN(schedch, proc_ptr); } /*===========================================================================* * 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 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; #if DEBUG_SCHED_CHECK if (caller_ptr->p_misc_flags & MF_SC_ACTIVE) minix_panic("MF_SC_ACTIVE already set", NO_NUM); #endif /* Set a flag to allow reliable tracing of leaving the system call. */ caller_ptr->p_misc_flags |= MF_SC_ACTIVE; } #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, RTS_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, RTS_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, RTS_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)) & RTS_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, RTS_NO_ENDPOINT)) { return EDSTDIED; } /* 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)) { /* 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, RTS_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, 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 != 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), RTS_NO_ENDPOINT)) { return ESRCDIED; } } /* 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) { 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, RTS_SLOT_FREE) || RTS_ISSET(*xpp, RTS_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); if ((*xpp)->p_misc_flags & MF_SIG_DELAY) sig_delay_done(*xpp); RTS_UNSET(*xpp, RTS_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) r= try_one(proc_addr(src_p), caller_ptr, NULL); 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, RTS_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, 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 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; ip_rts_flags & RTS_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. * 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. */ 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, RTS_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; 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); vmassert(!(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(src_ptr, dst_ptr, postponed) struct proc *src_ptr; struct proc *dst_ptr; int *postponed; { 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); /* 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 */ do_notify= FALSE; 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 */ 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 /* * 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 */ vmassert(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_SCHED_CHECK CHECK_RUNQUEUES; #endif NOREC_RETURN(enqueuefunc, ); } /*===========================================================================* * 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) { int q; /* scheduling queue to use */ #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 /* * the process was runnable without its quantum expired when dequeued. A * process with no time left should vahe been handled else and differently */ vmassert(rp->p_ticks_left); vmassert(q >= 0); vmassert(q < IDLE_Q || rp->p_endpoint == IDLE); q = rp->p_priority; /* 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 /* 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_SCHED_CHECK rp->p_ready = 1; CHECK_RUNQUEUES; #endif } /*===========================================================================* * 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 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 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++) { 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);); vmassert(!proc_is_runnable(rp)); if (priv(rp)->s_flags & BILLABLE) bill_ptr = rp; /* bill for system time */ return rp; } return NULL; } /*===========================================================================* * 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; rpp_priority > rp->p_max_priority) { /* update priority? */ if (proc_is_runnable(rp)) dequeue(rp); /* take off queue */ ticks_added += rp->p_quantum_size; /* do accounting */ rp->p_priority -= 1; /* raise priority */ if (proc_is_runnable(rp)) 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; }