Add _ublk_sleep() helper function that uses different sleep times
depending on whether tests run in parallel or sequential mode.

Usage: _ublk_sleep <normal_secs> <parallel_secs>

Export JOBS variable from Makefile so test scripts can detect parallel
execution, and use _ublk_sleep in test_part_02.sh to handle the
partition scan delay (1s normal, 5s parallel).

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 tools/testing/selftests/ublk/Makefile        |  1 +
 tools/testing/selftests/ublk/test_common.sh  | 10 ++++++++++
 tools/testing/selftests/ublk/test_part_02.sh |  2 +-
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/ublk/Makefile b/tools/testing/selftests/ublk/Makefile
index 37e012d3a8a7..1ceae611acb7 100644
--- a/tools/testing/selftests/ublk/Makefile
+++ b/tools/testing/selftests/ublk/Makefile
@@ -78,6 +78,7 @@ check:
 # JOBS>1: parallel execution with xargs -P
 # Usage: make run_null JOBS=4
 JOBS ?= 1
+export JOBS
 
 # Auto-detect test groups from TEST_PROGS (test_<group>_<num>.sh -> group)
 TEST_GROUPS := $(shell echo "$(TEST_PROGS)" | tr ' ' '\n' | \
diff --git a/tools/testing/selftests/ublk/test_common.sh b/tools/testing/selftests/ublk/test_common.sh
index 422882c32490..bd27a6875c1a 100755
--- a/tools/testing/selftests/ublk/test_common.sh
+++ b/tools/testing/selftests/ublk/test_common.sh
@@ -15,6 +15,16 @@ _have_program() {
 	return 1
 }
 
+# Sleep with awareness of parallel execution.
+# Usage: _ublk_sleep <normal_secs> <parallel_secs>
+_ublk_sleep() {
+	if [ "${JOBS:-1}" -gt 1 ]; then
+		sleep "$2"
+	else
+		sleep "$1"
+	fi
+}
+
 _get_disk_dev_t() {
 	local dev_id=$1
 	local dev
diff --git a/tools/testing/selftests/ublk/test_part_02.sh b/tools/testing/selftests/ublk/test_part_02.sh
index acd098deda3a..7d42ab4d6e83 100755
--- a/tools/testing/selftests/ublk/test_part_02.sh
+++ b/tools/testing/selftests/ublk/test_part_02.sh
@@ -33,7 +33,7 @@ _test_partition_scan_no_hang()
 	# The add command should return quickly because partition scan is async.
 	# Now sleep briefly to let the async partition scan work start and hit
 	# the delay in the fault_inject handler.
-	sleep 1
+	_ublk_sleep 1 5
 
 	# Kill the ublk daemon while partition scan is potentially blocked
 	# And check state transitions properly
-- 
2.47.0