selftests/bpf: Test rhtab kptr cancellation semanticsgrafted

Resizable hash-map updates and deletions must not perform full special-field
destruction in their caller context. In particular, a referenced kptr must
remain attached to the allocation until the memory allocator destructor can
release it safely.

Add separate coverage for both affected paths. The update test stores a task
kptr, replaces the ordinary value bytes with BPF_EXIST, and verifies that the
kptr survived. The delete test removes an element and exchanges its kptr
through the still-valid map-value pointer before the allocation is reclaimed.

Both cases observe a NULL kptr when rhtab uses bpf_obj_free_fields(). They
recover and release the reference after rhtab switches to cancellation
semantics.

Signed-off-by: Nuoqi Gui <gnq25@mails.tsinghua.edu.cn>
[ kkd: Split update and delete coverage and rewrote the commit log ]
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904104203.345917-5-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 36 insertions, 0 deletions

diff --git a/tools/perf/python/counting.py b/tools/perf/python/counting.py
new file mode 100755
index 000000000..02121d2bb
--- /dev/null
+++ b/tools/perf/python/counting.py
@@ -0,0 +1,36 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+# -*- python -*-
+# -*- coding: utf-8 -*-
+
+import argparse
+import perf
+
+def main(event: str):
+    evlist = perf.parse_events(event)
+
+    for evsel in evlist:
+        evsel.read_format = perf.FORMAT_TOTAL_TIME_ENABLED | perf.FORMAT_TOTAL_TIME_RUNNING
+
+    evlist.open()
+    evlist.enable()
+
+    count = 100000
+    while count > 0:
+        count -= 1
+
+    evlist.disable()
+
+    for evsel in evlist:
+        for cpu in evsel.cpus():
+            for thread in evsel.threads():
+                counts = evsel.read(cpu, thread)
+                print(f"For {evsel} val: {counts.val} enable: {counts.ena} run: {counts.run}")
+
+    evlist.close()
+
+if __name__ == '__main__':
+    ap = argparse.ArgumentParser()
+    ap.add_argument('-e', '--event', help="Events to open", default="cpu-clock,task-clock")
+    args = ap.parse_args()
+    main(args.event)