[PATCH] test: Have USDT "deferred" tests wait for dtrace to start

[eugene.loh@oracle.com]

From: Eugene Loh <eugene.loh@oracle.com>

Systemwide USDT tracing includes having dtrace track USDT processes
that start after it does.  Associated tests start dtrace first, wait
a few seconds, and then start processes to be traced.

Waiting "a few seconds" can be insufficient, especially on slower
systems or as more work is being performed during dtrace startup.

Change tests to wait for dtrace to start by polling on the output file.

Signed-off-by: Eugene Loh <eugene.loh@oracle.com>
---
 test/unittest/usdt/err.Z_no-w.sh      | 17 ++++++++++++++---
 test/unittest/usdt/tst.defer-Z.sh     | 17 ++++++++++++++---
 test/unittest/usdt/tst.defer.sh       | 17 ++++++++++++++---
 test/unittest/usdt/tst.nusdtprobes.sh | 16 +++++++++++++---
 4 files changed, 55 insertions(+), 12 deletions(-)

diff --git a/test/unittest/usdt/err.Z_no-w.sh b/test/unittest/usdt/err.Z_no-w.sh
index 3833b4400..4f129341d 100755
--- a/test/unittest/usdt/err.Z_no-w.sh
+++ b/test/unittest/usdt/err.Z_no-w.sh
@@ -34,9 +34,20 @@ testprov*:::foo
 	raise(SIGUSR1);
 }' &
 dtpid=$!
-sleep 4
-if [[ ! -d /proc/$dtpid ]]; then
-	echo ERROR dtrace died prematurely
+
+# Wait up to half of the timeout period for dtrace to start up.
+
+iter=$((timeout / 2))
+while [ $iter -gt 0 ]; do
+	sleep 1
+	if [ -e dtrace.out ]; then
+		break
+	fi
+	iter=$((iter - 1))
+done
+if [[ $iter -eq 0 ]]; then
+	echo ERROR starting DTrace job
+	cat dtrace.out
 	exit 1
 fi
 
diff --git a/test/unittest/usdt/tst.defer-Z.sh b/test/unittest/usdt/tst.defer-Z.sh
index 52e92eb6b..ff2c5cbf1 100755
--- a/test/unittest/usdt/tst.defer-Z.sh
+++ b/test/unittest/usdt/tst.defer-Z.sh
@@ -45,9 +45,20 @@ testprov*4:::bar
 	@[pid, 3] = sum(pid % 100);
 }' &
 dtpid=$!
-sleep 2
-if [[ ! -d /proc/$dtpid ]]; then
-	echo ERROR dtrace died
+
+# Wait up to half of the timeout period for dtrace to start up.
+
+iter=$((timeout / 2))
+while [ $iter -gt 0 ]; do
+	sleep 1
+	if [ -e dtrace.out ]; then
+		break
+	fi
+	iter=$((iter - 1))
+done
+if [[ $iter -eq 0 ]]; then
+	echo ERROR starting DTrace job
+	cat dtrace.out
 	exit 1
 fi
 
diff --git a/test/unittest/usdt/tst.defer.sh b/test/unittest/usdt/tst.defer.sh
index 02ed1a767..073af12d5 100755
--- a/test/unittest/usdt/tst.defer.sh
+++ b/test/unittest/usdt/tst.defer.sh
@@ -51,9 +51,20 @@ testprov*'$lastdigit':::bar
 	@[pid, 3] = sum(pid % 100);
 }' &
 dtpid=$!
-sleep 2
-if [[ ! -d /proc/$dtpid ]]; then
-	echo ERROR dtrace died
+
+# Wait up to half of the timeout period for dtrace to start up.
+
+iter=$((timeout / 2))
+while [ $iter -gt 0 ]; do
+	sleep 1
+	if [ -e dtrace.out ]; then
+		break
+	fi
+	iter=$((iter - 1))
+done
+if [[ $iter -eq 0 ]]; then
+	echo ERROR starting DTrace job
+	cat dtrace.out
 	kill -USR1 ${pids[0]}
 	wait       ${pids[0]}
 	exit 1
diff --git a/test/unittest/usdt/tst.nusdtprobes.sh b/test/unittest/usdt/tst.nusdtprobes.sh
index d2d80fe8d..f275f921f 100755
--- a/test/unittest/usdt/tst.nusdtprobes.sh
+++ b/test/unittest/usdt/tst.nusdtprobes.sh
@@ -105,9 +105,19 @@ for nusdt in "" "-xnusdtprobes=40" "-xnusdtprobes=39"; do
 		@[probeprov, probemod, probefunc, probename] = count();
 	}' &
 	dtpid=$!
-	sleep 2
-	if [[ ! -d /proc/$dtpid ]]; then
-		echo ERROR dtrace died
+
+	# Wait a little for dtrace to start up.
+
+	iter=$((timeout / 4))
+	while [ $iter -gt 0 ]; do
+		sleep 1
+		if [ -e dtrace.out ]; then
+			break
+		fi
+		iter=$((iter - 1))
+	done
+	if [[ $iter -eq 0 ]]; then
+		echo ERROR starting DTrace job
 		cat dtrace.out
 		exit 1
 	fi
-- 
2.43.5