set pthread stack size to at least PTHREAD_STACK_MIN

Setting the stacksize too small just causes
pthread_attr_setstacksize() to fail, leaving you with the default stack
size. On some architectures, the default stacksize is large, like 10Mb.
Since you start one waiter thread per multipath device, every 100
devices eats up 1Gb of memory.

The other problem is that when I actually read the pthread_attr_init man
page (it can fail. who knew?), I saw that it can fail with ENOMEM. Also,
that it had a function to free it, and that the result of reinitializing
an attr that hadn't been freed was undefined.  Clearly, this function
wasn't intended to be called over and over without ever freeing the
attr, which is how we've been using it in multipathd. So, in the spirit
of writing code to the interface, instead of to how it appears to be
currently implemented, how about this.

1 files changed, 38 insertions, 10 deletions

diff --git a/multipathd/main.c b/multipathd/main.c
index a5b61e6..f5e3e38 100644
--- a/multipathd/main.c
+++ b/multipathd/main.c
@@ -14,6 +14,7 @@
 #include <errno.h>
 #include <sys/time.h>
 #include <sys/resource.h>
+#include <limits.h>
 
 /*
  * libcheckers
@@ -1275,17 +1276,47 @@ set_oom_adj (int val)
 	fclose(fp);
 }
 
+void
+setup_thread_attr(pthread_attr_t *attr, size_t stacksize, int detached)
+{
+	if (pthread_attr_init(attr)) {
+		fprintf(stderr, "can't initialize thread attr: %s\n",
+			strerror(errno));
+		exit(1);
+	}
+	if (stacksize < PTHREAD_STACK_MIN)
+		stacksize = PTHREAD_STACK_MIN;
+
+	if (pthread_attr_setstacksize(attr, stacksize)) {
+		fprintf(stderr, "can't set thread stack size to %lu: %s\n",
+			(unsigned long)stacksize, strerror(errno));
+		exit(1);
+	}
+	if (detached && pthread_attr_setdetachstate(attr,
+						    PTHREAD_CREATE_DETACHED)) {
+		fprintf(stderr, "can't set thread to detached: %s\n",
+			strerror(errno));
+		exit(1);
+	}
+}
+
 static int
 child (void * param)
 {
 	pthread_t check_thr, uevent_thr, uxlsnr_thr;
-	pthread_attr_t attr;
+	pthread_attr_t log_attr, misc_attr;
 	struct vectors * vecs;
 
 	mlockall(MCL_CURRENT | MCL_FUTURE);
 
-	if (logsink)
-		log_thread_start();
+	setup_thread_attr(&misc_attr, 64 * 1024, 1);
+	setup_thread_attr(&waiter_attr, 32 * 1024, 1);
+
+	if (logsink) {
+		setup_thread_attr(&log_attr, 64 * 1024, 0);
+		log_thread_start(&log_attr);
+		pthread_attr_destroy(&log_attr);
+	}
 
 	condlog(2, "--------start up--------");
 	condlog(2, "read " DEFAULT_CONFIGFILE);
@@ -1356,13 +1387,10 @@ child (void * param)
 	/*
 	 * start threads
 	 */
-	pthread_attr_init(&attr);
-	pthread_attr_setstacksize(&attr, 64 * 1024);
-	pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
-
-	pthread_create(&check_thr, &attr, checkerloop, vecs);
-	pthread_create(&uevent_thr, &attr, ueventloop, vecs);
-	pthread_create(&uxlsnr_thr, &attr, uxlsnrloop, vecs);
+	pthread_create(&check_thr, &misc_attr, checkerloop, vecs);
+	pthread_create(&uevent_thr, &misc_attr, ueventloop, vecs);
+	pthread_create(&uxlsnr_thr, &misc_attr, uxlsnrloop, vecs);
+	pthread_attr_destroy(&misc_attr);
 
 	pthread_cond_wait(&exit_cond, &exit_mutex);