qemu-kvm/kvm-iotests-281-Test-lingering-timers.patch

From b56684f6c1bef4fb5bf87ac5a1106d3830c05ad0 Mon Sep 17 00:00:00 2001
From: Hanna Reitz <hreitz@redhat.com>
Date: Fri, 4 Feb 2022 12:10:10 +0100
Subject: [PATCH 4/6] iotests/281: Test lingering timers

RH-Author: Hanna Reitz <hreitz@redhat.com>
RH-MergeRequest: 117: block/nbd: Handle AioContext changes
RH-Commit: [4/6] aaad466941637a34224dc037bbea37d128b5676b
RH-Bugzilla: 2035185
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
RH-Acked-by: Eric Blake <eblake@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

Prior to "block/nbd: Delete reconnect delay timer when done" and
"block/nbd: Delete open timer when done", both of those timers would
remain scheduled even after successfully (re-)connecting to the server,
and they would not even be deleted when the BDS is deleted.

This test constructs exactly this situation:
(1) Configure an @open-timeout, so the open timer is armed, and
(2) Configure a @reconnect-delay and trigger a reconnect situation
    (which succeeds immediately), so the reconnect delay timer is armed.
Then we immediately delete the BDS, and sleep for longer than the
@open-timeout and @reconnect-delay.  Prior to said patches, this caused
one (or both) of the timer CBs to access already-freed data.

Accessing freed data may or may not crash, so this test can produce
false successes, but I do not know how to show the problem in a better
or more reliable way.  If you run this test on "block/nbd: Assert there
are no timers when closed" and without the fix patches mentioned above,
you should reliably see an assertion failure.
(But all other tests that use the reconnect delay timer (264 and 277)
will fail in that configuration, too; as will nbd-reconnect-on-open,
which uses the open timer.)

Remove this test from the quick group because of the two second sleep
this patch introduces.

(I decided to put this test case into 281, because the main bug this
series addresses is in the interaction of the NBD block driver and I/O
threads, which is precisely the scope of 281.  The test case for that
other bug will also be put into the test class added here.

Also, excuse the test class's name, I couldn't come up with anything
better.  The "yield" part will make sense two patches from now.)

Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
(cherry picked from commit eaf1e85d4ddefdbd197f393fa9c5acc7ba8133b0)

Conflict:
- @open-timeout was introduced after the 6.2 release, and has not been
  backported.  Consequently, there is no open_timer, and we can (and
  must) drop the respective parts of the test here.

Signed-off-by: Hanna Reitz <hreitz@redhat.com>
---
 tests/qemu-iotests/281     | 73 ++++++++++++++++++++++++++++++++++++--
 tests/qemu-iotests/281.out |  4 +--
 2 files changed, 73 insertions(+), 4 deletions(-)

diff --git a/tests/qemu-iotests/281 b/tests/qemu-iotests/281
index 956698083f..13c588be75 100755
--- a/tests/qemu-iotests/281
+++ b/tests/qemu-iotests/281
@@ -1,5 +1,5 @@
 #!/usr/bin/env python3
-# group: rw quick
+# group: rw
 #
 # Test cases for blockdev + IOThread interactions
 #
@@ -20,8 +20,9 @@
 #
 
 import os
+import time
 import iotests
-from iotests import qemu_img
+from iotests import qemu_img, QemuStorageDaemon
 
 image_len = 64 * 1024 * 1024
 
@@ -243,6 +244,74 @@ class TestBlockdevBackupAbort(iotests.QMPTestCase):
         # Hangs on failure, we expect this error.
         self.assert_qmp(result, 'error/class', 'GenericError')
 
+# Test for RHBZ#2033626
+class TestYieldingAndTimers(iotests.QMPTestCase):
+    sock = os.path.join(iotests.sock_dir, 'nbd.sock')
+    qsd = None
+
+    def setUp(self):
+        self.create_nbd_export()
+
+        # Simple VM with an NBD block device connected to the NBD export
+        # provided by the QSD
+        self.vm = iotests.VM()
+        self.vm.add_blockdev('nbd,node-name=nbd,server.type=unix,' +
+                             f'server.path={self.sock},export=exp,' +
+                             'reconnect-delay=1')
+
+        self.vm.launch()
+
+    def tearDown(self):
+        self.stop_nbd_export()
+        self.vm.shutdown()
+
+    def test_timers_with_blockdev_del(self):
+        # Stop and restart the NBD server, and do some I/O on the client to
+        # trigger a reconnect and start the reconnect delay timer
+        self.stop_nbd_export()
+        self.create_nbd_export()
+
+        result = self.vm.qmp('human-monitor-command',
+                             command_line='qemu-io nbd "write 0 512"')
+        self.assert_qmp(result, 'return', '')
+
+        # Reconnect is done, so the reconnect delay timer should be gone.
+        # (But there used to be a bug where it remained active, for which this
+        # is a regression test.)
+
+        # Delete the BDS to see whether the timer is gone.  If it is not,
+        # it will remain active, fire later, and then access freed data.
+        # (Or, with "block/nbd: Assert there are no timers when closed"
+        # applied, the assertion added in that patch will fail.)
+        result = self.vm.qmp('blockdev-del', node_name='nbd')
+        self.assert_qmp(result, 'return', {})
+
+        # Give the timer some time to fire (it has a timeout of 1 s).
+        # (Sleeping in an iotest may ring some alarm bells, but note that if
+        # the timing is off here, the test will just always pass.  If we kill
+        # the VM too early, then we just kill the timer before it can fire,
+        # thus not see the error, and so the test will pass.)
+        time.sleep(2)
+
+    def create_nbd_export(self):
+        assert self.qsd is None
+
+        # Simple NBD export of a null-co BDS
+        self.qsd = QemuStorageDaemon(
+            '--blockdev',
+            'null-co,node-name=null,read-zeroes=true',
+
+            '--nbd-server',
+            f'addr.type=unix,addr.path={self.sock}',
+
+            '--export',
+            'nbd,id=exp,node-name=null,name=exp,writable=true'
+        )
+
+    def stop_nbd_export(self):
+        self.qsd.stop()
+        self.qsd = None
+
 if __name__ == '__main__':
     iotests.main(supported_fmts=['qcow2'],
                  supported_protocols=['file'])
diff --git a/tests/qemu-iotests/281.out b/tests/qemu-iotests/281.out
index 89968f35d7..914e3737bd 100644
--- a/tests/qemu-iotests/281.out
+++ b/tests/qemu-iotests/281.out
@@ -1,5 +1,5 @@
-....
+.....
 ----------------------------------------------------------------------
-Ran 4 tests
+Ran 5 tests
 
 OK
-- 
2.27.0