MonetDB: Jan2014 - Fix potential race conditions, and avoid kill...

[Sjoerd Mullender]

Changeset: f3bdb8dcaebf for MonetDB
URL: http://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=f3bdb8dcaebf
Modified Files:
        monetdb5/modules/mal/mal_mapi.c
Branch: Jan2014
Log Message:

Fix potential race conditions, and avoid killing threads.


diffs (96 lines):

diff --git a/monetdb5/modules/mal/mal_mapi.c b/monetdb5/modules/mal/mal_mapi.c
--- a/monetdb5/modules/mal/mal_mapi.c
+++ b/monetdb5/modules/mal/mal_mapi.c
@@ -178,9 +178,13 @@ doChallenge(stream *in, stream *out) {
        MSscheduleClient(buf, challenge, bs, fdout);
 }
 
-static MT_Id listener[8];
-static int lastlistener=0;
-static int serveractive=TRUE;
+static volatile ATOMIC_TYPE nlistener = 0; /* nr of listeners */
+static volatile ATOMIC_TYPE serveractive = 0;
+static volatile ATOMIC_TYPE serverexiting = 0; /* listeners should exit */
+#ifdef ATOMIC_LOCK
+/* lock for all three ATOMIC_TYPE variables above */
+static MT_Lock atomicLock MT_LOCK_INITIALIZER("atomicLock");
+#endif
 
 static void
 SERVERlistenThread(SOCKET *Sock)
@@ -199,8 +203,7 @@ SERVERlistenThread(SOCKET *Sock)
                GDKfree(Sock);
        }
 
-       if (lastlistener < 8)
-               listener[lastlistener++] = MT_getpid();
+       (void) ATOMIC_INC(nlistener, atomicLock, "SERVERlistenThread");
 
        do {
                FD_ZERO(&fds);
@@ -221,7 +224,8 @@ SERVERlistenThread(SOCKET *Sock)
                        msgsock = usock;
 #endif
                retval = select((int)msgsock + 1, &fds, NULL, NULL, &tv);
-               if (GDKexiting())
+               if (ATOMIC_GET(serverexiting, atomicLock, "SERVERlistenThread") 
||
+                       GDKexiting())
                        break;
                if (retval == 0) {
                        /* nothing interesting has happened */
@@ -236,7 +240,7 @@ SERVERlistenThread(SOCKET *Sock)
                }
                if (sock != INVALID_SOCKET && FD_ISSET(sock, &fds)) {
                        if ((msgsock = accept(sock, (SOCKPTR)0, (socklen_t 
*)0)) == INVALID_SOCKET) {
-                               if (MT_geterrno() != EINTR || serveractive == 
FALSE) {
+                               if (MT_geterrno() != EINTR || 
!ATOMIC_GET(serveractive, atomicLock, "SERVERlistenThread")) {
                                        msg = "accept failed";
                                        goto error;
                                }
@@ -330,7 +334,9 @@ SERVERlistenThread(SOCKET *Sock)
                doChallenge(
                                socket_rastream(msgsock, "Server read"),
                                socket_wastream(msgsock, "Server write"));
-       } while (!GDKexiting());
+       } while (!ATOMIC_GET(serverexiting, atomicLock, "SERVERlistenThread") &&
+                        !GDKexiting());
+       (void) ATOMIC_DEC(nlistener, atomicLock, "SERVERlistenThread");
        return;
 error:
        fprintf(stderr, "!mal_mapi.listen: %s, terminating listener\n", msg);
@@ -599,12 +605,12 @@ SERVERlisten_port(int *ret, int *pid)
 str
 SERVERstop(int *ret)
 {
-       int i;
-
-printf("SERVERstop\n");
-       for( i=0; i< lastlistener; i++)
-               MT_kill_thread(listener[i]);
-       lastlistener = 0;
+fprintf(stderr, "SERVERstop\n");
+       ATOMIC_SET(serverexiting, 1, atomicLock, "SERVERstop");
+       /* wait until they all exited, but skip the wait if the whole
+        * system is going down */
+       while (ATOMIC_GET(nlistener, atomicLock, "SERVERstop") > 0 && 
!GDKexiting())
+               MT_sleep_ms(100);
        (void) ret;             /* fool compiler */
        return MAL_SUCCEED;
 }
@@ -614,14 +620,14 @@ str
 SERVERsuspend(int *res)
 {
        (void) res;
-       serveractive= FALSE;
+       ATOMIC_SET(serveractive, 0, atomicLock, "SERVERsuspend");
        return MAL_SUCCEED;
 }
 
 str
 SERVERresume(int *res)
 {
-       serveractive= TRUE;
+       ATOMIC_SET(serveractive, 1, atomicLock, "SERVERsuspend");
        (void) res;
        return MAL_SUCCEED;
 }
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