Hello Namhyung,
could you please adapt your patches from this series to Peter's latest
changes to unwind user and related perf support, especially his new
version c69993ecdd4d ("perf: Support deferred user unwind") available
at:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git perf/core
On 10/24/2025 3:02 PM, Peter Zijlstra wrote:
> On Thu, Oct 02, 2025 at 01:49:38PM -0400, Steven Rostedt wrote:
>> On Mon, 08 Sep 2025 13:53:23 -0400
>> Steven Rostedt <[email protected]> wrote:
>>
>>> +static int evlist__deliver_deferred_samples(struct evlist *evlist,
>>> + const struct perf_tool *tool,
>>> + union perf_event *event,
>>> + struct perf_sample *sample,
>>> + struct machine *machine)
>>> +{
>>> + struct deferred_event *de, *tmp;
>>> + struct evsel *evsel;
>>> + int ret = 0;
>>> +
>>> + if (!tool->merge_deferred_callchains) {
>>> + evsel = evlist__id2evsel(evlist, sample->id);
>>> + return tool->callchain_deferred(tool, event, sample,
>>> + evsel, machine);
>>> + }
>>> +
>>> + list_for_each_entry_safe(de, tmp, &evlist->deferred_samples, list) {
>>> + struct perf_sample orig_sample;
>>
>> orig_sample is not initialized and can then contain junk.
>>
>>> +
>>> + ret = evlist__parse_sample(evlist, de->event, &orig_sample);
>>> + if (ret < 0) {
>>> + pr_err("failed to parse original sample\n");
>>> + break;
>>> + }
>>> +
>>> + if (sample->tid != orig_sample.tid)
>>> + continue;
>>> +
>>> + if (event->callchain_deferred.cookie ==
>>> orig_sample.deferred_cookie)
>>> + sample__merge_deferred_callchain(&orig_sample, sample);
>>
>> The sample__merge_deferred_callchain() initializes both
>> orig_sample.deferred_callchain and the callchain. But now that it's not
>> being called, it can cause the below free to happen with junk as the
>> callchain. This needs:
>>
>> else
>> orig_sample.deferred_callchain = false;
>
> Ah, so I saw crashes from here and just deleted both free()s and got on
> with things ;-)
This needs to be properly resolved. In the meantime I am using Steven's
suggestion above to continue my work on unwind user sframe (s390).
>
>>> +
>>> + evsel = evlist__id2evsel(evlist, orig_sample.id);
>>> + ret = evlist__deliver_sample(evlist, tool, de->event,
>>> + &orig_sample, evsel,> machine); +
>>> + if (orig_sample.deferred_callchain)
>>> + free(orig_sample.callchain);
>>> +
>>> + list_del(&de->list);
>>> + free(de);
>>> +
>>> + if (ret)
>>> + break;
>>> + }
>>> + return ret;
>>> +}
>>
>> -- Steve
Thanks and regards,
Jens
--
Jens Remus
Linux on Z Development (D3303)
+49-7031-16-1128 Office
[email protected]
IBM
IBM Deutschland Research & Development GmbH; Vorsitzender des Aufsichtsrats:
Wolfgang Wendt; Geschäftsführung: David Faller; Sitz der Gesellschaft:
Böblingen; Registergericht: Amtsgericht Stuttgart, HRB 243294
IBM Data Privacy Statement: https://www.ibm.com/privacy/
