1010 *
1111 *
1212 * IDENTIFICATION
13- * $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.84 1998/06/08 22:28:26 momjian Exp $
13+ * $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.85 1998/06/09 04:06:12 momjian Exp $
1414 *
1515 * NOTES
1616 *
113113typedef struct bkend
114114{
115115int pid ;/* process id of backend */
116+ long cancel_key ;/* cancel key for cancels for this backend */
116117}Backend ;
117118
118119/* list of active backends. For garbage collection only now. */
@@ -198,7 +199,14 @@ staticsigset_toldsigmask,
198199static int orgsigmask = sigblock (0 );
199200#endif
200201
202+ /*
203+ * State for assigning random salts and cancel keys.
204+ * Also, the global MyCancelKey passes the cancel key assigned to a given
205+ * backend from the postmaster to that backend (via fork).
206+ */
207+
201208static unsignedint random_seed = 0 ;
209+ long MyCancelKey = 0 ;
202210
203211extern char * optarg ;
204212extern int optind ,
@@ -612,17 +620,22 @@ ServerLoop(void)
612620return (STATUS_ERROR );
613621}
614622
615- if (random_seed == 0 )
623+ /*
624+ * Select a random seed at the time of first receiving a request.
625+ */
626+ while (random_seed == 0 )
616627{
617628gettimeofday (& later ,& tz );
618629
619630/*
620631 *We are not sure how much precision is in tv_usec, so we
621- *swap the nibbles of 'later' and XOR them with 'now'
632+ *swap the nibbles of 'later' and XOR them with 'now'.
633+ * On the off chance that the result is 0, we loop until
634+ * it isn't.
622635 */
623636random_seed = now .tv_usec ^
624637((later .tv_usec <<16 ) |
625- ((unsigned int )( later .tv_usec & 0xffff0000 ) >>16 ));
638+ ((later .tv_usec >>16 ) & 0xffff ));
626639}
627640
628641/*
@@ -1085,6 +1098,14 @@ BackendStartup(Port *port)
10851098}
10861099#endif
10871100
1101+ /*
1102+ * Compute the cancel key that will be assigned to this backend.
1103+ * The backend will have its own copy in the forked-off process'
1104+ * value of MyCancelKey, so that it can transmit the key to the
1105+ * frontend.
1106+ */
1107+ MyCancelKey = PostmasterRandom ();
1108+
10881109if (DebugLvl > 2 )
10891110{
10901111char * * p ;
@@ -1098,17 +1119,21 @@ BackendStartup(Port *port)
10981119fprintf (stderr ,"-----------------------------------------\n" );
10991120}
11001121
1122+ /* Flush all stdio channels just before fork,
1123+ * to avoid double-output problems.
1124+ */
1125+ fflush (NULL );
1126+
11011127if ((pid = fork ())== 0 )
11021128{/* child */
11031129if (DoBackend (port ))
11041130{
11051131fprintf (stderr ,"%s child[%d]: BackendStartup: backend startup failed\n" ,
1106- progname ,pid );
1107- /* use _exit to keep from double-flushing stdio */
1108- _exit (1 );
1132+ progname , (int )getpid ());
1133+ exit (1 );
11091134}
11101135else
1111- _exit (0 );
1136+ exit (0 );
11121137}
11131138
11141139/* in parent */
@@ -1140,6 +1165,7 @@ BackendStartup(Port *port)
11401165}
11411166
11421167bn -> pid = pid ;
1168+ bn -> cancel_key = MyCancelKey ;
11431169DLAddHead (BackendList ,DLNewElem (bn ));
11441170
11451171ActiveBackends = TRUE;