《ORANGE’S：一个操作系统的实现》读书笔记（二十八）文件系统（三）文章代码

#include "type.h" #include "config.h" #include "const.h" #include "protect.h" #include "console.h" #include "tty.h" #include "proc.h" #include "proto.h" #include "string.h" #include "fs.h" #include "global.h" PRIVATE void block(PROCESS* p); PRIVATE void unblock(PROCESS* p); PRIVATE int deadlock(int src, int dest); PRIVATE int msg_send(PROCESS* current, int dest, MESSAGE* m); PRIVATE int msg_recevie(PROCESS* current, int src, MESSAGE* m); PUBLIC void scheduld() { PROCESS* p; int greatest_ticks = 0; while (!greatest_ticks) { for (p = &FIRST_PROC; p <= &LAST_PROC; p++) { if (p->p_flags == 0) { if (p->ticks > greatest_ticks) { greatest_ticks = p->ticks; p_proc_ready = p; } } } if (!greatest_ticks) { for (p = &FIRST_PROC; p < &LAST_PROC; p++) { if (p->p_flags == 0) { p->ticks = p->priority; } } } } } /** * <Ring 0> The core routine of system call 'sendrec()'. * * @param function SEND or RECEIVE * @param src_dest To/From whom the message is transferred. * @param m Ptr to the MESSAGE body. * @param p The caller proc. * * @return Zero if success. */ PUBLIC int sys_sendrec(int function, int src_dest, MESSAGE* m, PROCESS* p) { assert(k_reenter == 0); /* make sure we are not in ring0 */ assert((src_dest >= 0 && src_dest < NR_TASKS + NR_PROCS) || src_dest == ANY || src_dest == INTERRUPT); int ret = 0; int caller = proc2pid(p); MESSAGE* mla = (MESSAGE*)va2la(caller, m); mla->source = caller; /** * Actually we have the third message type: BOTH. However, it is not * allowed to be passed to the kernel directly. Kernel doesn't know * it at all. It is transformed into a SEND followed by a RECEVIE * by 'send_recv()' */ if (function == SEND) { ret = msg_send(p, src_dest, m); if (ret != 0) { return ret; } } else if (function == RECEIVE) { ret = msg_recevie(p, src_dest, m); if (ret != 0) { return ret; } } else { panic("{sys_sendrec} invalid function: %d (SEND:%d, RECEIVE:%d).", function, SEND, RECEIVE); } return 0; } /** * <Ring 1~3> IPC syscall. * * It is an encapsulation of `sendrec', * invoking `sendrec' directly should be avoided * * @param function SEND, RECEIVE or BOTH * @param src_dest The caller's proc_nr * @param msg Pointer to the MESSAGE struct * * @return always 0. *****************************************************************************/ PUBLIC int send_recv(int function, int src_dest, MESSAGE* msg) { int ret = 0; if (function == RECEIVE) memset(msg, 0, sizeof(MESSAGE)); switch (function) { case BOTH: ret = sendrec(SEND, src_dest, msg); if (ret == 0) ret = sendrec(RECEIVE, src_dest, msg); break; case SEND: case RECEIVE: ret = sendrec(function, src_dest, msg); break; default: assert((function == BOTH) || (function == SEND) || (function == RECEIVE)); break; } return ret; } /** * <Ring 0~1> Calculate the linear address of a certain segment of a given proc. * * @param p Whose (the proc ptr). * @param idx Whick (one proc has more than one segments). * * @return The required linear address. */ PUBLIC int ldt_seg_linear(PROCESS *p, int idx) { DESCRIPTOR *d = &p->ldts[idx]; return d->base_high << 24 | d->base_mid << 16 | d->base_low; } /** * <Ring 0~1> Virtual addr --> Linear addr. * * @param pid PID of the proc whose address is to be calculated. * @param va Virtual address. * * @return The liner address for the given virtual address. */ PUBLIC void* va2la(int pid, void* va) { PROCESS *p = &proc_table[pid]; u32 seg_base = ldt_seg_linear(p, INDEX_LDT_RW); u32 la = seg_base + (u32)va; if (pid < NR_TASKS + NR_PROCS) { assert(la == (u32)va); } return (void*)la; } /** * <Ring 0~3> Clear up a MESSAGE by setting each byte to 0. * * @param p The message to be cleared. */ PUBLIC void reset_msg(MESSAGE* p) { memset(p, 0, sizeof(MESSAGE)); } /** * <Ring 0> This routine is called after 'p_flags' has been set (!= 0), it * calls 'schedule()' to choose another proc as the 'proc_ready'. * * @attention This routine does not change 'p_flags'. Make sure the 'p_flags' * of the proc to be blocked has been set properly. * * @param p The proc to be blocked. */ PRIVATE void block(PROCESS* p) { assert(p->p_flags); scheduld(); } /** * <Ring 0> This is a dummy routine. It does nothing actually. When it is * called, the 'p_flags' should have been cleared (== 0). * * @param p The unblocked proc. */ PRIVATE void unblock(PROCESS* p) { assert(p->p_flags == 0); } /** * <Ring 0> Check whether it is safe to send a message from src to dest. * The routine will detect if the messaging graph contains a cycle. For * instance, if we have procs trying to send messages like this: * A -> B -> C -> A, then a deadlock occurs, because all of then will * wait forever. If no cycles detected, it is considered as safe. * * @param src Who wants to send message. * @param dest To whom the message is sent. * * @return Zero if success. */ PRIVATE int deadlock(int src, int dest) { PROCESS* p = proc_table + dest; while (1) { if (p->p_flags & SENDING) { if (p->p_sendto == src) { /* print the chain */ p = proc_table + dest; printl("=_=%s", p->p_name); do { assert(p->p_msg); p = proc_table + p->p_sendto; printl("->%s", p->p_name); } while (p != proc_table + src); printl("=_="); return 1; } p = proc_table + p->p_sendto; } else { break; } } return 0; } /** * <Ring 0> Send a message to the dest proc. If dest is blocked waiting for * the message, copy the message to it and unblock dest. Otherwise the caller * will be blocked and appended to the dest's sending queue. * * @param current The caller, the sender. * @param dest To whom the message is sent. * @param m The message. * * @return Zero if success. */ PRIVATE int msg_send(PROCESS* current, int dest, MESSAGE* m) { PROCESS* sender = current; PROCESS* p_dest = proc_table + dest; /* proc dest */ assert(proc2pid(sender) != dest); /* check for deadlock here */ if (deadlock(proc2pid(sender), dest)) { panic(">>DEADLOCK<< %s->%s", sender->p_name, p_dest->p_name); } if ((p_dest->p_flags & RECEIVING) && /* dest is waiting for the msg */ (p_dest->p_recvfrom == proc2pid(sender) || p_dest->p_recvfrom == ANY)) { assert(p_dest->p_msg); assert(m); phys_copy(va2la(dest, p_dest->p_msg), va2la(proc2pid(sender), m), sizeof(MESSAGE)); p_dest->p_msg = 0; p_dest->p_flags &= ~RECEIVING; /* dest has received the msg */ p_dest->p_recvfrom = NO_TASK; unblock(p_dest); assert(p_dest->p_flags == 0); assert(p_dest->p_msg == 0); assert(p_dest->p_recvfrom == NO_TASK); assert(p_dest->p_sendto == NO_TASK); assert(sender->p_flags == 0); assert(sender->p_msg == 0); assert(sender->p_recvfrom == NO_TASK); assert(sender->p_sendto == NO_TASK); } else { /* dest is not waiting for the msg */ sender->p_flags