netdev - [PATCH AUTOSEL 6.17-5.4] selftests: Replace sleep with slowwait

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Message-ID: <20251025160905.3857885-431-sashal@kernel.org>
Date: Sat, 25 Oct 2025 12:01:02 -0400
From: Sasha Levin <sashal@...nel.org>
To: patches@...ts.linux.dev,
	stable@...r.kernel.org
Cc: David Ahern <dsahern@...nel.org>,
	Simon Horman <horms@...nel.org>,
	Jakub Kicinski <kuba@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	davem@...emloft.net,
	edumazet@...gle.com,
	pabeni@...hat.com,
	netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 6.17-5.4] selftests: Replace sleep with slowwait

From: David Ahern <dsahern@...nel.org>

[ Upstream commit 2f186dd5585c3afb415df80e52f71af16c9d3655 ]

Replace the sleep in kill_procs with slowwait.

Signed-off-by: David Ahern <dsahern@...nel.org>
Reviewed-by: Simon Horman <horms@...nel.org>
Link: https://patch.msgid.link/20250910025828.38900-2-dsahern@kernel.org
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---

LLM Generated explanations, may be completely bogus:

YES

- What changed
  - Replaces a fixed delay with a condition-based wait in `kill_procs()`
    so test cleanup actually completes before proceeding:
    `tools/testing/selftests/net/fcnal-test.sh:192`.
  - Old behavior: `sleep 1` after `killall nettest ping ping6`.
  - New behavior: `slowwait 2 sh -c 'test -z "$(pgrep
    "^(nettest|ping|ping6)$")"'` to poll until those processes are gone,
    up to 2 seconds.

- Why it matters
  - `kill_procs()` is called at test start to ensure a clean slate:
    `tools/testing/selftests/net/fcnal-test.sh:161-166`. A fixed sleep
    can be too short on slower or loaded systems, leaving straggler
    `ping`/`ping6`/`nettest` processes that interfere with subsequent
    tests, causing flakiness or false failures. The condition-based wait
    removes that flakiness by verifying process exit.

- How `slowwait` works (and why it’s safe)
  - `slowwait()` is a common helper in net selftests that polls every
    100ms until a command succeeds or a timeout is hit:
    `tools/testing/selftests/net/lib.sh:105-110`. It uses `loopy_wait
    "sleep 0.1" ...`, causing no architectural or API changes, and only
    affects selftest behavior.
  - This is consistent with broader selftests usage (e.g.,
    `tools/testing/selftests/net/rtnetlink.sh:314`,
    `tools/testing/selftests/net/forwarding/lib.sh:566`), standardizing
    on proven patterns already used across the test suite.

- Scope and risk
  - Selftests-only change; no in-kernel code touched.
  - Small and contained; no interface changes.
  - Failure mode is limited: if the processes don’t exit, `slowwait`
    times out in 2s and `kill_procs()`’s non-zero exit code is not fatal
    in callers (no `set -e`); the tests proceed, but the added wait
    significantly lowers flakiness vs. a blind `sleep 1`.
  - The `pgrep` anchored regex `^(nettest|ping|ping6)$` targets the
    exact processes, avoiding false positives.

- Stable backport fit
  - Fixes a real test bug (flaky cleanup) that affects test reliability
    on stable trees.
  - Minimal risk, no architectural changes, not a new feature.
  - Improves determinism of selftests run against stable kernels,
    aligning with stable policy to accept selftest reliability fixes.

Conclusion: This is a low-risk, selftests-only robustness fix that
improves test reliability and should be backported.

 tools/testing/selftests/net/fcnal-test.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/fcnal-test.sh b/tools/testing/selftests/net/fcnal-test.sh
index cf535c23a959a..dfd368371fb3c 100755
--- a/tools/testing/selftests/net/fcnal-test.sh
+++ b/tools/testing/selftests/net/fcnal-test.sh
@@ -189,7 +189,7 @@ show_hint()
 kill_procs()
 {
 	killall nettest ping ping6 >/dev/null 2>&1
-	sleep 1
+	slowwait 2 sh -c 'test -z "$(pgrep '"'^(nettest|ping|ping6)$'"')"'
 }
 
 set_ping_group()
-- 
2.51.0