make the worker thread size configurable and choose a sensible small default

README.rst

@@ -492,6 +492,11 @@ Parameter            CLI Option Description
 -------------------- ---------- ----------------------------------------------------------------------------------------- -------
 ``nworkers``                    Number of worker threads used to send messages to the message broker(s).                  1
 -------------------- ---------- ----------------------------------------------------------------------------------------- -------
+``worker.stack``                Stack size for worker threads started by trackrdrd.                                       131072
+                                Note: mq modules may start additional threads to which this limit does not apply
+                                Observed actual stack sizes are <64k, so the default leaves plenty of room.               (128 KB)
+                                Increase only if segmentation faults on stack addresses are observed
+-------------------- ---------- ----------------------------------------------------------------------------------------- -------
 ``max.records``                 The maximum number of buffered records waiting to be sent to message brokers.             1024
 -------------------- ---------- ----------------------------------------------------------------------------------------- -------
 ``max.reclen``                  The maximum length of a data record in characters. Should be at least as large the        1024

src/config.c

@@ -140,6 +140,7 @@ CONF_Add(const char *lval, const char *rval)
     confUnsigned("maxkeylen", maxkeylen);
     confUnsigned("qlen.goal", qlen_goal);
     confUnsigned("nworkers", nworkers);
+    confUnsigned("worker.stack", worker_stack);
     confUnsigned("restarts", restarts);
     confUnsigned("restart.pause", restart_pause);
     confUnsigned("thread.restarts", thread_restarts);
@@ -239,6 +240,7 @@ CONF_Init(void)
     config.mq_module[0] = '\0';
     config.mq_config_file[0] = '\0';
     config.nworkers = 1;
+    config.worker_stack = 128 * 1024;
     config.restarts = 1;
     config.restart_pause = 1;
     config.thread_restarts = 1;

src/test/Makefile.am

@@ -99,4 +99,6 @@ test_worker_LDADD = \
 	../data.$(OBJEXT) \
 	../assert.$(OBJEXT) \
 	../vtim.$(OBJEXT) \
+	../config.$(OBJEXT) \
+	../config_common.$(OBJEXT) \
 	-L${VARNISH_PKG_LIB}/varnish -lvarnish

src/test/test_worker.c

@@ -109,11 +109,9 @@ static char
 
     printf("... testing worker initialization\n");
 
-    config.max_records = DEF_MAX_RECORDS;
-    config.max_reclen = DEF_MAX_RECLEN;
-    config.maxkeylen = DEF_MAXKEYLEN;
+    CONF_Init();
+
     config.nworkers = NWORKERS;
-    config.chunk_size = DEF_CHUNK_SIZE;
     strcpy(config.mq_config_file, MQ_CONFIG);
 
     error = mqf.global_init(config.nworkers, config.mq_config_file);

src/trackrdrd.h

@@ -219,6 +219,7 @@ struct config {
 #define DEF_QLEN_GOAL 512
 
     unsigned	nworkers;
+    size_t	worker_stack;
     unsigned	restarts;
     unsigned	restart_pause;
     unsigned	thread_restarts;

src/worker.c

@@ -405,22 +405,37 @@ WRK_Init(void)
     return 0;
 }
 
+void
+wrk_pthread_attr_init(pthread_attr_t *attr)
+{
+    AZ(pthread_attr_init(attr));
+    AZ(pthread_attr_setstacksize(attr, config.worker_stack));
+}
+
 void
 WRK_Start(void)
 {
+    pthread_attr_t attr;
+
+    wrk_pthread_attr_init(&attr);
     run = 1;
     for (int i = 0; i < config.nworkers; i++) {
         CHECK_OBJ_NOTNULL(thread_data[i].wrk_data, WORKER_DATA_MAGIC);
-        AZ(pthread_create(&thread_data[i].worker, NULL, wrk_main,
+        AZ(pthread_create(&thread_data[i].worker, &attr, wrk_main,
                           thread_data[i].wrk_data));
     }
+    AZ(pthread_attr_destroy(&attr));
 }
 
 int
 WRK_Restart(void)
 {
+    int err = 0;
     worker_data_t *wrk;
-    
+    pthread_attr_t attr;
+
+    wrk_pthread_attr_init(&attr);
+
     for (int i = 0; i < config.nworkers; i++) {
         CHECK_OBJ_NOTNULL(thread_data[i].wrk_data, WORKER_DATA_MAGIC);
         wrk = thread_data[i].wrk_data;
@@ -442,18 +457,20 @@ WRK_Restart(void)
             wrk->restarts++;
             MON_StatsUpdate(STATS_RESTART, 0, 0);
             wrk->state = WRK_NOTSTARTED;
-            if (pthread_create(&thread_data[i].worker, NULL, wrk_main, wrk)
+            if (pthread_create(&thread_data[i].worker, &attr, wrk_main, wrk)
                 != 0) {
                 /* EAGAIN means we've hit a system limit trying to restart
                    threads, so it's time to give up. Any other errno is a
                    programming error.
                 */
                 assert(errno == EAGAIN);
-                return errno;
+                err = errno;
+                break;
             }
         }
     }
-    return 0;
+    AZ(pthread_attr_destroy(&attr));
+    return err;
 }
 
 void