From 35497c7c3369718cae08bb5dcf95dd487d214008 Mon Sep 17 00:00:00 2001
From: Frantisek Sumsal <frantisek@sumsal.cz>
Date: Fri, 10 Sep 2021 17:16:51 +0200
Subject: [PATCH] test: coverage for #19946

---
 test/TEST-64-UDEV-STORAGE/test.sh | 16 +++++++++++++
 test/units/testsuite-64.sh        | 37 +++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/test/TEST-64-UDEV-STORAGE/test.sh b/test/TEST-64-UDEV-STORAGE/test.sh
index accbe092554..2b9d0735e34 100755
--- a/test/TEST-64-UDEV-STORAGE/test.sh
+++ b/test/TEST-64-UDEV-STORAGE/test.sh
@@ -230,6 +230,22 @@ EOF
     test_run_one "${1:?}"
 }
 
+# Test case for issue https://github.com/systemd/systemd/issues/19946
+testcase_simultaneous_events() {
+    local qemu_opts=("-device virtio-scsi-pci,id=scsi")
+    local partdisk="${TESTDIR:?}/simultaneousevents.img"
+
+    dd if=/dev/zero of="$partdisk" bs=1M count=110
+    qemu_opts+=(
+        "-device scsi-hd,drive=drive1,serial=deadbeeftest"
+        "-drive format=raw,cache=unsafe,file=$partdisk,if=none,id=drive1"
+    )
+
+    KERNEL_APPEND="systemd.setenv=TEST_FUNCTION_NAME=${FUNCNAME[0]} ${USER_KERNEL_APPEND:-}"
+    QEMU_OPTIONS="${qemu_opts[*]} ${USER_QEMU_OPTIONS:-}"
+    test_run_one "${1:?}"
+}
+
 # Allow overriding which tests should be run from the "outside", useful for manual
 # testing (make -C test/... TESTCASES="testcase1 testcase2")
 if [[ -v "TESTCASES" && -n "$TESTCASES" ]]; then
diff --git a/test/units/testsuite-64.sh b/test/units/testsuite-64.sh
index 8e8f27d23c3..ab688207bf3 100755
--- a/test/units/testsuite-64.sh
+++ b/test/units/testsuite-64.sh
@@ -140,6 +140,43 @@ EOF
     rm -fr "$mpoint"
 }
 
+testcase_simultaneous_events() {
+    local blockdev part partscript
+
+    blockdev="$(readlink -f /dev/disk/by-id/scsi-*_deadbeeftest)"
+    partscript="$(mktemp)"
+
+    if [[ ! -b "$blockdev" ]]; then
+        echo "ERROR: failed to find the test SCSI block device"
+        return 1
+    fi
+
+    cat >"$partscript" <<EOF
+$(printf 'name="test%d", size=2M\n' {1..50})
+EOF
+
+    # Initial partition table
+    sfdisk -q -X gpt "$blockdev" <"$partscript"
+
+    # Delete the partitions, immediatelly recreate them, wait for udev to settle
+    # down, and then check if we have any dangling symlinks in /dev/disk/. Rinse
+    # and repeat.
+    #
+    # On unpatched udev versions the delete-recreate cycle may trigger a race
+    # leading to dead symlinks in /dev/disk/
+    for i in {1..100}; do
+        sfdisk -q --delete "$blockdev"
+        sfdisk -q -X gpt "$blockdev" <"$partscript"
+
+        if ((i % 10 == 0)); then
+            udevadm settle
+            helper_check_device_symlinks
+        fi
+    done
+
+    rm -f "$partscript"
+}
+
 : >/failed
 
 udevadm settle