1 175b8a53 2004-04-21 devnull /*
  2 175b8a53 2004-04-21 devnull  * This needs to be callable from a signal handler, so it has been
  3 175b8a53 2004-04-21 devnull  * written to avoid locks.  The only lock is the one used to acquire
  4 175b8a53 2004-04-21 devnull  * an entry in the table, and we make sure that acquiring is done
  5 175b8a53 2004-04-21 devnull  * when not in a handler.  Lookup and delete do not need locks.
  6 175b8a53 2004-04-21 devnull  * It's a scan-forward hash table.  To avoid breaking chains, 
  7 175b8a53 2004-04-21 devnull  * T ((void*)-1) is used as a non-breaking nil.
  8 175b8a53 2004-04-21 devnull  */
  9 175b8a53 2004-04-21 devnull 
 10 fd04aace 2003-11-23 devnull #include <u.h>
 11 fd04aace 2003-11-23 devnull #include <libc.h>
 12 fd04aace 2003-11-23 devnull #include "9proc.h"
 13 fd04aace 2003-11-23 devnull 
 14 175b8a53 2004-04-21 devnull enum { PIDHASH = 1021 };
 15 175b8a53 2004-04-21 devnull 
 16 175b8a53 2004-04-21 devnull #define T ((void*)-1)
 17 175b8a53 2004-04-21 devnull static Uproc *alluproc[PIDHASH];
 18 175b8a53 2004-04-21 devnull static int allupid[PIDHASH];
 19 fd04aace 2003-11-23 devnull static Lock uproclock;
 20 fd04aace 2003-11-23 devnull 
 21 f1bfc54e 2004-05-14 devnull void
 22 f1bfc54e 2004-05-14 devnull _clearuproc(void)
 23 f1bfc54e 2004-05-14 devnull {
 24 f1bfc54e 2004-05-14 devnull 	int i;
 25 f1bfc54e 2004-05-14 devnull 
 26 f1bfc54e 2004-05-14 devnull 	/* called right after fork - no locking needed */
 27 f1bfc54e 2004-05-14 devnull 	for(i=0; i<PIDHASH; i++)
 28 f1bfc54e 2004-05-14 devnull 		if(alluproc[i] != T && alluproc[i] != 0)
 29 f1bfc54e 2004-05-14 devnull 			free(alluproc[i]);
 30 f1bfc54e 2004-05-14 devnull 	memset(alluproc, 0, sizeof alluproc);
 31 f1bfc54e 2004-05-14 devnull 	memset(allupid, 0, sizeof allupid);
 32 f1bfc54e 2004-05-14 devnull }
 33 f1bfc54e 2004-05-14 devnull 		
 34 fd04aace 2003-11-23 devnull Uproc*
 35 175b8a53 2004-04-21 devnull _p9uproc(int inhandler)
 36 fd04aace 2003-11-23 devnull {
 37 175b8a53 2004-04-21 devnull 	int i, h, pid;
 38 fd04aace 2003-11-23 devnull 	Uproc *up;
 39 fd04aace 2003-11-23 devnull 
 40 175b8a53 2004-04-21 devnull 	/* for now, assume getpid is fast or cached */
 41 fd04aace 2003-11-23 devnull 	pid = getpid();
 42 175b8a53 2004-04-21 devnull 
 43 175b8a53 2004-04-21 devnull 	/*
 44 175b8a53 2004-04-21 devnull 	 * this part - the lookup - needs to run without locks
 45 175b8a53 2004-04-21 devnull 	 * so that it can safely be called from within the notify handler.
 46 175b8a53 2004-04-21 devnull 	 * notify calls _p9uproc, and fork and rfork call _p9uproc
 47 175b8a53 2004-04-21 devnull 	 * in both parent and child, so if we're in a signal handler,
 48 175b8a53 2004-04-21 devnull 	 * we should find something in the table.
 49 175b8a53 2004-04-21 devnull 	 */
 50 175b8a53 2004-04-21 devnull 	h = pid%PIDHASH;
 51 175b8a53 2004-04-21 devnull 	for(i=0; i<PIDHASH; i++){
 52 175b8a53 2004-04-21 devnull 		up = alluproc[h];
 53 175b8a53 2004-04-21 devnull 		if(up == nil)
 54 175b8a53 2004-04-21 devnull 			break;
 55 175b8a53 2004-04-21 devnull 		if(allupid[h] == pid)
 56 fd04aace 2003-11-23 devnull 			return up;
 57 175b8a53 2004-04-21 devnull 		if(++h == PIDHASH)
 58 175b8a53 2004-04-21 devnull 			h = 0;
 59 fd04aace 2003-11-23 devnull 	}
 60 fd04aace 2003-11-23 devnull 
 61 b1455f33 2004-04-30 devnull 	if(inhandler){
 62 b1455f33 2004-04-30 devnull 		fprint(2, "%s: did not find uproc for pid %d in signal handler\n", argv0, pid);
 63 b1455f33 2004-04-30 devnull 		abort();	
 64 b1455f33 2004-04-30 devnull 	}
 65 fd04aace 2003-11-23 devnull 
 66 175b8a53 2004-04-21 devnull 	/* need to allocate */
 67 175b8a53 2004-04-21 devnull 	while((up = mallocz(sizeof(Uproc), 1)) == nil)
 68 fd04aace 2003-11-23 devnull 		sleep(1000);
 69 fd04aace 2003-11-23 devnull 
 70 2e965b33 2004-05-05 devnull 	/* fprint(2, "alloc uproc for pid %d\n", pid); */
 71 b1455f33 2004-04-30 devnull 	up->pid = pid;
 72 175b8a53 2004-04-21 devnull 	lock(&uproclock);
 73 175b8a53 2004-04-21 devnull 	h = pid%PIDHASH;
 74 175b8a53 2004-04-21 devnull 	for(i=0; i<PIDHASH; i++){
 75 175b8a53 2004-04-21 devnull 		if(alluproc[h]==T || alluproc[h]==nil){
 76 175b8a53 2004-04-21 devnull 			alluproc[h] = up;
 77 175b8a53 2004-04-21 devnull 			allupid[h] = pid;
 78 0b424d7b 2004-04-21 devnull 			unlock(&uproclock);
 79 175b8a53 2004-04-21 devnull 			return up;
 80 175b8a53 2004-04-21 devnull 		}
 81 175b8a53 2004-04-21 devnull 		if(++h == PIDHASH)
 82 175b8a53 2004-04-21 devnull 			h = 0;
 83 175b8a53 2004-04-21 devnull 	}
 84 fd04aace 2003-11-23 devnull 	unlock(&uproclock);
 85 175b8a53 2004-04-21 devnull 
 86 175b8a53 2004-04-21 devnull 	/* out of pids! */
 87 175b8a53 2004-04-21 devnull 	sysfatal("too many processes in uproc table");
 88 175b8a53 2004-04-21 devnull 	return nil;
 89 fd04aace 2003-11-23 devnull }
 90 fd04aace 2003-11-23 devnull 
 91 fd04aace 2003-11-23 devnull void
 92 fd04aace 2003-11-23 devnull _p9uprocdie(void)
 93 fd04aace 2003-11-23 devnull {
 94 175b8a53 2004-04-21 devnull 	Uproc *up;
 95 175b8a53 2004-04-21 devnull 	int pid, i, h;
 96 fd04aace 2003-11-23 devnull 
 97 fd04aace 2003-11-23 devnull 	pid = getpid();
 98 2e965b33 2004-05-05 devnull 	/* fprint(2, "reap uproc for pid %d\n", pid); */
 99 175b8a53 2004-04-21 devnull 	h = pid%PIDHASH;
100 175b8a53 2004-04-21 devnull 	for(i=0; i<PIDHASH; i++){
101 175b8a53 2004-04-21 devnull 		up = alluproc[h];
102 175b8a53 2004-04-21 devnull 		if(up == nil)
103 175b8a53 2004-04-21 devnull 			break;
104 175b8a53 2004-04-21 devnull 		if(up == T)
105 175b8a53 2004-04-21 devnull 			continue;
106 175b8a53 2004-04-21 devnull 		if(allupid[h] == pid){
107 175b8a53 2004-04-21 devnull 			up = alluproc[h];
108 175b8a53 2004-04-21 devnull 			alluproc[h] = T;
109 fd04aace 2003-11-23 devnull 			free(up);
110 175b8a53 2004-04-21 devnull 			allupid[h] = 0;
111 fd04aace 2003-11-23 devnull 		}
112 fd04aace 2003-11-23 devnull 	}
113 fd04aace 2003-11-23 devnull }