From 2b97956af60810cd382b86b9ce9aea421b889861 Mon Sep 17 00:00:00 2001 From: Nuoqi Gui Date: Fri, 4 Sep 2026 12:41:55 +0200 Subject: selftests/bpf: Test rhtab kptr cancellation semantics 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 [ kkd: Split update and delete coverage and rewrote the commit log ] Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260904104203.345917-5-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- tools/perf/python/tracepoint.py | 55 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) create mode 100755 tools/perf/python/tracepoint.py (limited to 'tools/perf/python/tracepoint.py') diff --git a/tools/perf/python/tracepoint.py b/tools/perf/python/tracepoint.py new file mode 100755 index 000000000..15b0c8268 --- /dev/null +++ b/tools/perf/python/tracepoint.py @@ -0,0 +1,55 @@ +#! /usr/bin/env python +# SPDX-License-Identifier: GPL-2.0 +# -*- python -*- +# -*- coding: utf-8 -*- + +import perf + +def change_proctitle(): + try: + import setproctitle + setproctitle.setproctitle("tracepoint.py") + except: + print("Install the setproctitle python package to help with top and friends") + +def main(): + change_proctitle() + cpus = perf.cpu_map() + threads = perf.thread_map(-1) + evlist = perf.parse_events("sched:sched_switch", cpus, threads) + # Disable tracking of mmaps and similar that are unnecessary. + for ev in evlist: + ev.tracking = False + # Configure evsels with default record options. + evlist.config() + # Simplify the sample_type and read_format of evsels + for ev in evlist: + ev.sample_type = ev.sample_type & ~perf.SAMPLE_IP + ev.read_format = 0 + + evlist.open() + evlist.mmap() + evlist.enable(); + + while True: + evlist.poll(timeout = -1) + for cpu in cpus: + event = evlist.read_on_cpu(cpu) + if not event: + continue + + if not isinstance(event, perf.sample_event): + continue + + print("time %u prev_comm=%s prev_pid=%d prev_prio=%d prev_state=0x%x ==> next_comm=%s next_pid=%d next_prio=%d" % ( + event.sample_time, + event.prev_comm, + event.prev_pid, + event.prev_prio, + event.prev_state, + event.next_comm, + event.next_pid, + event.next_prio)) + +if __name__ == '__main__': + main() -- cgit v1.3.1