Re: [PATCH for-11.1?] qemu-iotest 161: fix race

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Jul 28, 2026 at 07:39:16PM +0300, Michael Tokarev wrote:
> qemu-iotest 161 fails intermittedly due to a race condition:
> 
> qemu:block / io-qcow2-161             ERROR            2.08s   exit status 1
> ――――――――――――――――――――――――――――――――――― ✀  ―――――――――――――――――――――――――――――――――――――
> stderr:
> --- tests/qemu-iotests/161.out
> +++ scratch/qcow2-file-161/161.out.bad
> @@ -34,6 +34,8 @@
>  *** Commit and then change an option on the backing file
> 
>  Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=1048576
> +qemu-img: TEST_DIR/t.IMGFMT.base: Failed to get "write" lock
> +Is another process using the image [TEST_DIR/t.IMGFMT.base]?
>  Formatting 'TEST_DIR/t.IMGFMT.int', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
>  Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.int backing_fmt=IMGFMT
>  { 'execute': 'qmp_capabilities' }
> 
> This test is run right after a previous test, where we've
> killed qemu process which holds the test image open.

When you say "previous test" can you clarify the scenario you're
hitting. The tests run with TEST_DIR set to a name that is unique
to the test name + format. eg

   qemu.git/build/scratch/raw-file-101

so...

> It looks like when the next test is started (with creating
> the image files), old qemu is still running, so we're racing
> with that qemu, and qemu-img is unable to lock the image file
> properly.

...iiuc this can only happen if the exact same test + format is
re-run ?

Is that what you're doing ?

If so, rather than deleting the image we should do two
things

 * Make sure tests clean up after themselves if we find one that
   is buggy and leaves stuff running
 
 * Make TEST_DIR more unique by adding the current test hardness
   PID to is, so re-runs can never clash

diff --git a/tests/qemu-iotests/testrunner.py b/tests/qemu-iotests/testrunner.py
index dbe2dddc32..9c7f9d733e 100644
--- a/tests/qemu-iotests/testrunner.py
+++ b/tests/qemu-iotests/testrunner.py
@@ -259,7 +259,7 @@ def do_run_test(self, test: str) -> TestResult:
         for d in ['TEST_DIR', 'SOCK_DIR']:
             env[d] = os.path.join(
                 env[d],
-                f"{self.env.imgfmt}-{self.env.imgproto}-{f_test.name}")
+                f"{self.env.imgfmt}-{self.env.imgproto}-{f_test.name}-{os.getpid()}")
             Path(env[d]).mkdir(parents=True, exist_ok=True)
 
         test_dir = env['TEST_DIR']



With regards,
Daniel
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