Re: [PATCH 2/4] selftests/vfio: Wait out transient -EBUSY on open/bind

[David Matlack <dmatlack@google.com>]

On 2026-09-01 03:53 PM, Alex Williamson wrote:
> If a test is killed, for example due to timeout, fput can be delayed,
> allowing the subsequent test to be started while the failing test still
> holds the device open count elevated.  This results in a cascade of
> failures as each subsequent test fails on open, blocked by the single
> user requirement at the group or device cdev file.
> 
> We can make the test framework more robust, and allow better
> identification of specific failing scenarios, by waiting-out transient
> -EBUSY failures on group open and cdev bind.
> 
> The 20s retry window is heuristically determined in testing on a system
> where scheduling can be significantly delayed due to SMI handling of
> platform errors generated from the mix-and-match test.
> 
> The SR-IOV uAPI and IOMMUFD setup tests retain their non-retry bind
> paths as these are not expected to encounter process kills due to
> underlying platform error handling variability.
> 
> Assisted-by: Qwen3.8-27B
> Signed-off-by: Alex Williamson <alex.williamson@nvidia.com>

I think we should fix this in kselftest_harness.h instead.

If the poll() times out the harness issues SIGKILL but then does not
wait for the process to finish exiting (waitpid(..., WNOHANG). If we
drop WNOHANG then the harness will wait for the killed process to exit
before proceeding with the next test case.

diff --git a/tools/testing/selftests/kselftest_harness.h b/tools/testing/selftests/kselftest_harness.h
index 1e459619fe86..150bd690ca7b 100644
--- a/tools/testing/selftests/kselftest_harness.h
+++ b/tools/testing/selftests/kselftest_harness.h
@@ -1008,7 +1008,7 @@ static void __wait_for_test(struct __test_metadata *t)
         /* signal process group */
         kill(-(t->pid), SIGKILL);
     }
-    child = waitpid(t->pid, &status, WNOHANG);
+    child = waitpid(t->pid, &status, 0);
     if (child == -1 && errno != EINTR) {
         t->exit_code = KSFT_FAIL;
         fprintf(TH_LOG_STREAM,