591 lines
23 KiB
C
Executable file
591 lines
23 KiB
C
Executable file
/* This file contains essentially all of the process and message handling.
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* Together with "mpx.s" it forms the lowest layer of the MINIX kernel.
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* There is one entry point from the outside:
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*
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* sys_call: a system call, i.e., the kernel is trapped with an INT
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*
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* As well as several entry points used from the interrupt and task level:
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*
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* lock_notify: notify a process of a system event
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* lock_send: send a message to a process
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* lock_ready: put a process on one of the ready queues
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* lock_unready: remove a process from the ready queues
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* lock_sched: a process has run too long; schedule another one
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*
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* Changes:
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* , 2005 better protection in sys_call() (Jorrit N. Herder)
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* May 26, 2005 optimized message passing functions (Jorrit N. Herder)
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* May 24, 2005 new, queued NOTIFY system call (Jorrit N. Herder)
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* Oct 28, 2004 new, non-blocking SEND and RECEIVE (Jorrit N. Herder)
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* Oct 28, 2004 rewrite of sys_call() function (Jorrit N. Herder)
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* Aug 19, 2004 generalized multilevel scheduling (Jorrit N. Herder)
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*
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* The code here is critical to make everything work and is important for the
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* overall performance of the system. A large fraction of the code deals with
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* list manipulation. To make this both easy to understand and fast to execute
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* pointer pointers are used throughout the code. Pointer pointers prevent
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* exceptions for the head or tail of a linked list.
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*
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* node_t *queue, *new_node; // assume these as global variables
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* node_t **xpp = &queue; // get pointer pointer to head of queue
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* while (*xpp != NULL) // find last pointer of the linked list
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* xpp = &(*xpp)->next; // get pointer to next pointer
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* *xpp = new_node; // now replace the end (the NULL pointer)
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* new_node->next = NULL; // and mark the new end of the list
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*
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* For example, when adding a new node to the end of the list, one normally
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* makes an exception for an empty list and looks up the end of the list for
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* nonempty lists. As shown above, this is not required with pointer pointers.
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*/
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#include "kernel.h"
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#include <minix/callnr.h>
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#include <minix/com.h>
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#include "proc.h"
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#include "debug.h"
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#include "ipc.h"
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#include "sendmask.h"
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/* Scheduling and message passing functions. The functions are available to
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* other parts of the kernel through lock_...(). The lock temporarily disables
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* interrupts to prevent race conditions.
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*/
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FORWARD _PROTOTYPE( int mini_send, (struct proc *caller_ptr, int dst,
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message *m_ptr, unsigned flags) );
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FORWARD _PROTOTYPE( int mini_receive, (struct proc *caller_ptr, int src,
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message *m_ptr, unsigned flags) );
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FORWARD _PROTOTYPE( int mini_notify, (struct proc *caller_ptr, int dst,
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message *m_ptr ) );
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FORWARD _PROTOTYPE( void ready, (struct proc *rp) );
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FORWARD _PROTOTYPE( void unready, (struct proc *rp) );
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FORWARD _PROTOTYPE( void sched, (int queue) );
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FORWARD _PROTOTYPE( void pick_proc, (void) );
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#define BuildMess(m,n) \
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(m).NOTIFY_SOURCE = (n)->n_source, \
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(m).NOTIFY_TYPE = (n)->n_type, \
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(m).NOTIFY_FLAGS = (n)->n_flags, \
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(m).NOTIFY_ARG = (n)->n_arg;
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#if (CHIP == INTEL)
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#define CopyMess(s,sp,sm,dp,dm) \
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cp_mess(s, (sp)->p_memmap[D].mem_phys, (vir_bytes)sm, (dp)->p_memmap[D].mem_phys, (vir_bytes)dm)
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#endif /* (CHIP == INTEL) */
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#if (CHIP == M68000)
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/* M68000 does not have cp_mess() in assembly like INTEL. Declare prototype
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* for cp_mess() here and define the function below. Also define CopyMess.
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*/
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#endif /* (CHIP == M68000) */
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/*===========================================================================*
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* sys_call *
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*===========================================================================*/
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PUBLIC int sys_call(call_nr, src_dst, m_ptr)
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int call_nr; /* system call number and flags */
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int src_dst; /* src to receive from or dst to send to */
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message *m_ptr; /* pointer to message in the caller's space */
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{
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/* System calls are done by trapping to the kernel with an INT instruction.
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* The trap is caught and sys_call() is called to send or receive a message
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* (or both). The caller is always given by 'proc_ptr'.
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*/
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register struct proc *caller_ptr = proc_ptr; /* get pointer to caller */
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int function = call_nr & SYSCALL_FUNC; /* get system call function */
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unsigned flags = call_nr & SYSCALL_FLAGS; /* get flags */
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int mask_entry; /* bit to check in send mask */
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int result; /* the system call's result */
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vir_bytes vb; /* message buffer pointer as vir_bytes */
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vir_clicks vlo, vhi; /* virtual clicks containing message to send */
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/* Check if the process has privileges for the requested call. Calls to the
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* kernel may only be SENDREC, because tasks always reply and may not block
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* if the caller doesn't do receive().
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*/
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if (! (caller_ptr->p_call_mask & (1 << function)) ||
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(iskerneltask(src_dst) && function != SENDREC))
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return(ECALLDENIED);
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/* Require a valid source and/ or destination process, unless echoing. */
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if (! (isokprocn(src_dst) || src_dst == ANY || function == ECHO))
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return(EBADSRCDST);
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/* Check validity of message pointer. */
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vb = (vir_bytes) m_ptr;
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vlo = vb >> CLICK_SHIFT; /* vir click for bottom of message */
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vhi = (vb + MESS_SIZE - 1) >> CLICK_SHIFT; /* vir click for top of msg */
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#if ALLOW_GAP_MESSAGES
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/* This check allows a message to be anywhere in data or stack or gap.
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* It will have to be made more elaborate later for machines which
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* don't have the gap mapped.
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*/
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if (vlo < caller_ptr->p_memmap[D].mem_vir || vlo > vhi ||
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vhi >= caller_ptr->p_memmap[S].mem_vir + caller_ptr->p_memmap[S].mem_len)
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return(EFAULT);
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#else
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/* Check for messages wrapping around top of memory or outside data seg. */
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if (vhi < vlo ||
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vhi - caller_ptr->p_memmap[D].mem_vir >= caller_ptr->p_memmap[D].mem_len)
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return(EFAULT);
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#endif
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/* Now check if the call is known and try to perform the request. The only
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* system calls that exist in MINIX are sending and receiving messages.
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* - SENDREC: combines SEND and RECEIVE in a single system call
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* - SEND: sender blocks until its message has been delivered
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* - RECEIVE: receiver blocks until an acceptable message has arrived
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* - NOTIFY: sender continues; either directly deliver the message or
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* queue the notification message until it can be delivered
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* - ECHO: the message directly will be echoed to the sender
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*/
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switch(function) {
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case SENDREC: /* has FRESH_ANSWER flag */
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/* fall through */
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case SEND:
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if (! isalive(src_dst)) {
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result = EDEADDST; /* cannot send to the dead */
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break;
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}
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mask_entry = isuser(src_dst) ? USER_PROC_NR : src_dst;
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if (! isallowed(caller_ptr->p_sendmask, mask_entry)) {
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kprintf("WARNING: sys_call denied %d ", caller_ptr->p_nr);
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kprintf("sending to %d\n", proc_addr(src_dst)->p_nr);
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result = ECALLDENIED; /* call denied by send mask */
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break;
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}
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result = mini_send(caller_ptr, src_dst, m_ptr, flags);
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if (function == SEND || result != OK) {
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break; /* done, or SEND failed */
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} /* fall through for SENDREC */
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case RECEIVE:
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result = mini_receive(caller_ptr, src_dst, m_ptr, flags);
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break;
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case NOTIFY:
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result = mini_notify(caller_ptr, src_dst, m_ptr);
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break;
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case ECHO:
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kprintf("Echo message from process %s\n", proc_nr(caller_ptr));
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CopyMess(caller_ptr->p_nr, caller_ptr, m_ptr, caller_ptr, m_ptr);
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result = OK;
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break;
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default:
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result = EBADCALL; /* illegal system call */
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}
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/* Now, return the result of the system call to the caller. */
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return(result);
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}
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/*===========================================================================*
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* mini_send *
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*===========================================================================*/
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PRIVATE int mini_send(caller_ptr, dst, m_ptr, flags)
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register struct proc *caller_ptr; /* who is trying to send a message? */
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int dst; /* to whom is message being sent? */
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message *m_ptr; /* pointer to message buffer */
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unsigned flags; /* system call flags */
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{
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/* Send a message from 'caller_ptr' to 'dst'. If 'dst' is blocked waiting
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* for this message, copy the message to it and unblock 'dst'. If 'dst' is
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* not waiting at all, or is waiting for another source, queue 'caller_ptr'.
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*/
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register struct proc *dst_ptr = proc_addr(dst);
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register struct proc **xpp;
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register struct proc *xp;
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/* Check for deadlock by 'caller_ptr' and 'dst' sending to each other. */
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xp = dst_ptr;
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while (xp->p_flags & SENDING) { /* check while sending */
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xp = proc_addr(xp->p_sendto); /* get xp's destination */
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if (xp == caller_ptr) return(ELOCKED); /* deadlock if cyclic */
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}
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/* Check if 'dst' is blocked waiting for this message. The destination's
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* SENDING flag may be set when its SENDREC call blocked while sending.
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*/
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if ( (dst_ptr->p_flags & (RECEIVING | SENDING)) == RECEIVING &&
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(dst_ptr->p_getfrom == ANY || dst_ptr->p_getfrom == caller_ptr->p_nr)) {
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/* Destination is indeed waiting for this message. */
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CopyMess(caller_ptr->p_nr, caller_ptr, m_ptr, dst_ptr,
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dst_ptr->p_messbuf);
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if ((dst_ptr->p_flags &= ~RECEIVING) == 0) ready(dst_ptr);
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} else if ( ! (flags & NON_BLOCKING)) {
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/* Destination is not waiting. Block and queue caller. */
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caller_ptr->p_messbuf = m_ptr;
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if (caller_ptr->p_flags == 0) unready(caller_ptr);
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caller_ptr->p_flags |= SENDING;
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caller_ptr->p_sendto = dst;
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/* Process is now blocked. Put in on the destination's queue. */
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xpp = &dst_ptr->p_caller_q; /* find end of list */
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while (*xpp != NIL_PROC) xpp = &(*xpp)->p_q_link;
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*xpp = caller_ptr; /* add caller to end */
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caller_ptr->p_q_link = NIL_PROC; /* mark new end of list */
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} else {
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return(ENOTREADY);
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}
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return(OK);
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}
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/*===========================================================================*
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* mini_receive *
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*===========================================================================*/
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PRIVATE int mini_receive(caller_ptr, src, m_ptr, flags)
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register struct proc *caller_ptr; /* process trying to get message */
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int src; /* which message source is wanted */
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message *m_ptr; /* pointer to message buffer */
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unsigned flags; /* system call flags */
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{
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/* A process or task wants to get a message. If a message is already queued,
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* acquire it and deblock the sender. If no message from the desired source
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* is available block the caller, unless the flags don't allow blocking.
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*/
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register struct proc **xpp;
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register struct notification **ntf_q_pp;
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message m;
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int bit_nr;
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/* Check to see if a message from desired source is already available.
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* The caller's SENDING flag may be set if SENDREC couldn't send. If it is
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* set, the process should be blocked.
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*/
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if (!(caller_ptr->p_flags & SENDING)) {
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/* Check caller queue. Use pointer pointers to keep code simple. */
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xpp = &caller_ptr->p_caller_q;
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while (*xpp != NIL_PROC) {
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if (src == ANY || src == proc_nr(*xpp)) {
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/* Found acceptable message. Copy it and update status. */
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CopyMess((*xpp)->p_nr, *xpp, (*xpp)->p_messbuf, caller_ptr, m_ptr);
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if (((*xpp)->p_flags &= ~SENDING) == 0) ready(*xpp);
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*xpp = (*xpp)->p_q_link; /* remove from queue */
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return(OK); /* report success */
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}
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xpp = &(*xpp)->p_q_link; /* proceed to next */
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}
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/* Check if there are pending notifications, except for SENDREC. */
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if (! (flags & FRESH_ANSWER)) {
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ntf_q_pp = &caller_ptr->p_ntf_q; /* get pointer pointer */
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while (*ntf_q_pp != NULL) {
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if (src == ANY || src == (*ntf_q_pp)->n_source) {
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/* Found notification. Assemble and copy message. */
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BuildMess(m, *ntf_q_pp);
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CopyMess((*ntf_q_pp)->n_source, proc_addr(HARDWARE), &m,
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caller_ptr, m_ptr);
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/* Remove notification from queue and bit map. */
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bit_nr = (int) (*ntf_q_pp - ¬ify_buffer[0]);
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*ntf_q_pp = (*ntf_q_pp)->n_next;/* remove from queue */
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free_bit(bit_nr, notify_bitmap, NR_NOTIFY_BUFS);
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return(OK); /* report success */
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}
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ntf_q_pp = &(*ntf_q_pp)->n_next; /* proceed to next */
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}
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}
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}
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/* No suitable message is available or the caller couldn't send in SENDREC.
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* Block the process trying to receive, unless the flags tell otherwise.
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*/
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if ( ! (flags & NON_BLOCKING)) {
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caller_ptr->p_getfrom = src;
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caller_ptr->p_messbuf = m_ptr;
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if (caller_ptr->p_flags == 0) unready(caller_ptr);
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caller_ptr->p_flags |= RECEIVING;
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return(OK);
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} else {
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return(ENOTREADY);
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}
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}
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/*===========================================================================*
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* mini_notify *
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*===========================================================================*/
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PRIVATE int mini_notify(caller_ptr, dst, m_ptr)
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register struct proc *caller_ptr; /* process trying to notify */
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int dst; /* which process to notify */
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message *m_ptr; /* pointer to message buffer */
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{
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register struct proc *dst_ptr = proc_addr(dst);
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register struct notification *ntf_p ;
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register struct notification **ntf_q_pp;
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int ntf_index;
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message ntf_mess;
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/* Check to see if target is blocked waiting for this message. A process
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* can be both sending and receiving during a SENDREC system call.
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*/
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if ( (dst_ptr->p_flags & (RECEIVING|SENDING)) == RECEIVING &&
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(dst_ptr->p_getfrom == ANY || dst_ptr->p_getfrom == caller_ptr->p_nr)) {
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/* Destination is indeed waiting for this message. */
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CopyMess(proc_nr(caller_ptr), caller_ptr, m_ptr,
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dst_ptr, dst_ptr->p_messbuf);
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dst_ptr->p_flags &= ~RECEIVING; /* deblock destination */
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if (dst_ptr->p_flags == 0) ready(dst_ptr);
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return(OK);
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}
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/* Destination is not ready. Add the notification to the pending queue.
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* Get pointer to notification message. Don't copy if already in kernel.
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*/
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if (! istaskp(caller_ptr)) {
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CopyMess(proc_nr(caller_ptr), caller_ptr, m_ptr,
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proc_addr(HARDWARE), &ntf_mess);
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m_ptr = &ntf_mess;
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}
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/* Enqueue the message. Existing notifications with the same source
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* and type are overwritten with newer ones. New notifications that
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* are not yet on the list are added to the end.
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*/
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ntf_q_pp = &dst_ptr->p_ntf_q;
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while (*ntf_q_pp != NULL) {
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/* Replace notifications with same source and type. */
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if ((*ntf_q_pp)->n_type == m_ptr->NOTIFY_TYPE &&
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(*ntf_q_pp)->n_source == proc_nr(caller_ptr)) {
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(*ntf_q_pp)->n_flags = m_ptr->NOTIFY_FLAGS;
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(*ntf_q_pp)->n_arg = m_ptr->NOTIFY_ARG;
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return(OK);
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}
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ntf_q_pp = &(*ntf_q_pp)->n_next;
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}
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/* Add to end of queue (found above). Get a free notification buffer. */
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if ((ntf_index = alloc_bit(notify_bitmap, NR_NOTIFY_BUFS)) < 0)
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return(ENOSPC);
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ntf_p = ¬ify_buffer[ntf_index]; /* get pointer to buffer */
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ntf_p->n_source = proc_nr(caller_ptr);/* store notification data */
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ntf_p->n_type = m_ptr->NOTIFY_TYPE;
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ntf_p->n_flags = m_ptr->NOTIFY_FLAGS;
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ntf_p->n_arg = m_ptr->NOTIFY_ARG;
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*ntf_q_pp = ntf_p; /* add to end of queue */
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ntf_p->n_next = NULL; /* mark new end of queue */
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return(OK);
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}
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/*==========================================================================*
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* lock_notify *
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*==========================================================================*/
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PUBLIC int lock_notify(dst, m_ptr)
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int dst; /* to whom is message being sent? */
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message *m_ptr; /* pointer to message buffer */
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{
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/* Safe gateway to mini_notify() for tasks and interrupt handlers. MINIX
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* kernel is not reentrant, which means to interrupts are disabled after
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* the first kernel entry (hardware interrupt, trap, or exception). Locking
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* work is done by temporarily disabling interrupts.
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*/
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int result;
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/* Exception or interrupt occurred, thus already locked. */
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if (k_reenter >= 0) {
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result = mini_notify(proc_addr(HARDWARE), dst, m_ptr);
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}
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/* Call from task level, locking is required. */
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else {
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lock(0, "notify");
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result = mini_notify(proc_ptr, dst, m_ptr);
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unlock(0);
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}
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return(result);
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}
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/*===========================================================================*
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* pick_proc *
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*===========================================================================*/
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PRIVATE void pick_proc()
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{
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/* Decide who to run now. A new process is selected by setting 'next_ptr'.
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* When a fresh user (or idle) process is selected, record it in 'bill_ptr',
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* so the clock task can tell who to bill for system time.
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*/
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register struct proc *rp; /* process to run */
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int q; /* iterate over queues */
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/* Check each of the scheduling queues for ready processes. The number of
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* queues is defined in proc.h, and priorities are set in the task table.
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* The lowest queue contains IDLE, which is always ready.
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*/
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for (q=0; q < NR_SCHED_QUEUES; q++) {
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if ( (rp = rdy_head[q]) != NIL_PROC) {
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next_ptr = rp; /* run process 'rp' next */
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if (isuserp(rp) || isidlep(rp)) /* possible bill 'rp' */
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bill_ptr = rp;
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return;
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}
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}
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}
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/*===========================================================================*
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* ready *
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*===========================================================================*/
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PRIVATE void ready(rp)
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register struct proc *rp; /* this process is now runnable */
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{
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/* Add 'rp' to one of the queues of runnable processes. */
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register int q = rp->p_priority; /* scheduling queue to use */
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|
register struct proc **xpp; /* iterate over queue */
|
|
|
|
#if ENABLE_K_DEBUGGING
|
|
if(rp->p_ready) {
|
|
kprintf("ready() already ready process\n", NO_NUM);
|
|
}
|
|
rp->p_ready = 1;
|
|
#endif
|
|
|
|
/* Processes, in principle, are added to the end of the queue. However,
|
|
* user processes are added in front of the queue, because this is a bit
|
|
* fairer to I/O bound processes.
|
|
*/
|
|
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 (isuserp(rp)) { /* 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 */
|
|
}
|
|
|
|
/* Run 'rp' next if it has a higher priority than 'proc_ptr' or 'next_ptr'.
|
|
* This actually should be done via pick_proc(), but the message passing
|
|
* functions rely on this side-effect. High priorities have a lower number.
|
|
*/
|
|
if (next_ptr && next_ptr->p_priority > rp->p_priority) next_ptr = rp;
|
|
else if (proc_ptr->p_priority > rp->p_priority) next_ptr = rp;
|
|
}
|
|
|
|
/*===========================================================================*
|
|
* unready *
|
|
*===========================================================================*/
|
|
PRIVATE void unready(rp)
|
|
register struct proc *rp; /* this process is no longer runnable */
|
|
{
|
|
/* A process has blocked. See ready for a description of the queues. */
|
|
|
|
register int q = rp->p_priority; /* queue to use */
|
|
register struct proc **xpp; /* iterate over queue */
|
|
register struct proc *prev_xp;
|
|
|
|
#if ENABLE_K_DEBUGGING
|
|
if(!rp->p_ready) {
|
|
kprintf("unready() already unready process\n", NO_NUM);
|
|
}
|
|
rp->p_ready = 0;
|
|
#endif
|
|
|
|
/* Side-effect for tasks: check if the task's stack still is ok? */
|
|
if (istaskp(rp)) {
|
|
if (*rp->p_stguard != STACK_GUARD)
|
|
panic("stack overrun by task", proc_nr(rp));
|
|
}
|
|
|
|
/* Now make sure that the process is not in its ready queue. Remove the
|
|
* process if it is found. A process can be made unready even if it is not
|
|
* running by being sent a signal that kills it.
|
|
*/
|
|
prev_xp = NIL_PROC;
|
|
for (xpp = &rdy_head[q]; *xpp != NIL_PROC; xpp = &(*xpp)->p_nextready) {
|
|
|
|
if (*xpp == rp) { /* found process to remove */
|
|
*xpp = (*xpp)->p_nextready; /* replace with next chain */
|
|
if (rp == rdy_tail[q]) /* queue tail removed */
|
|
rdy_tail[q] = prev_xp; /* set new tail */
|
|
if (rp == proc_ptr || rp == next_ptr) /* active process removed */
|
|
pick_proc(); /* pick new process to run */
|
|
break;
|
|
}
|
|
prev_xp = *xpp; /* save previous in chain */
|
|
}
|
|
}
|
|
|
|
/*===========================================================================*
|
|
* sched *
|
|
*===========================================================================*/
|
|
PRIVATE void sched(q)
|
|
int q; /* scheduling queue to use */
|
|
{
|
|
/* The current process has run too long. If another low priority (user)
|
|
* process is runnable, put the current process on the end of the user queue,
|
|
* possibly promoting another user to head of the queue.
|
|
*/
|
|
if (rdy_head[q] == NIL_PROC) return; /* return for empty queue */
|
|
|
|
/* One or more user processes queued. */
|
|
rdy_tail[q]->p_nextready = rdy_head[q]; /* add expired to end */
|
|
rdy_tail[q] = rdy_head[q]; /* set new queue tail */
|
|
rdy_head[q] = rdy_head[q]->p_nextready; /* set new queue head */
|
|
rdy_tail[q]->p_nextready = NIL_PROC; /* mark new queue end */
|
|
|
|
pick_proc(); /* select next to run */
|
|
}
|
|
|
|
|
|
/*==========================================================================*
|
|
* lock_send *
|
|
*==========================================================================*/
|
|
PUBLIC int lock_send(dst, m_ptr)
|
|
int dst; /* to whom is message being sent? */
|
|
message *m_ptr; /* pointer to message buffer */
|
|
{
|
|
/* Safe gateway to mini_send() for tasks. */
|
|
int result;
|
|
lock(2, "send");
|
|
result = mini_send(proc_ptr, dst, m_ptr, NON_BLOCKING);
|
|
unlock(2);
|
|
return(result);
|
|
}
|
|
|
|
|
|
/*==========================================================================*
|
|
* lock_ready *
|
|
*==========================================================================*/
|
|
PUBLIC void lock_ready(rp)
|
|
struct proc *rp; /* this process is now runnable */
|
|
{
|
|
/* Safe gateway to ready() for tasks. */
|
|
lock(3, "ready");
|
|
ready(rp);
|
|
unlock(3);
|
|
}
|
|
|
|
/*==========================================================================*
|
|
* lock_unready *
|
|
*==========================================================================*/
|
|
PUBLIC void lock_unready(rp)
|
|
struct proc *rp; /* this process is no longer runnable */
|
|
{
|
|
/* Safe gateway to unready() for tasks. */
|
|
lock(4, "unready");
|
|
unready(rp);
|
|
unlock(4);
|
|
}
|
|
|
|
/*==========================================================================*
|
|
* lock_sched *
|
|
*==========================================================================*/
|
|
PUBLIC void lock_sched(queue)
|
|
int queue;
|
|
{
|
|
/* Safe gateway to sched() for tasks. */
|
|
lock(5, "sched");
|
|
sched(queue);
|
|
unlock(5);
|
|
}
|
|
|